Name: purification of viral dna for the identification of associated viral and cellular proteins
Uploaded: 2017-08-31T15:00:00
Description: Watch this Scientific Journal Video about Purification of Viral DNA for the Identification of Associated Viral and Cellular Proteins at JoVE.com

We acknowledge Hannah Fox for help in the preparation of this manuscript. This work was supported by the NIH grant R01AI030612.

1. Cell Culture, Viral Infection, and EdC Labeling (Figure 1)
The following protocol involves working with viruses. Please refer to your institution&#39;s bio-safety protocols regarding safe handling of viruses and other biological agents. This protocol was approved by the Institutional Review Board of the University of Pittsburgh.
<ol>
	<li>Trypsinize a confluent 150 cm2 tissue culture flask of MRC-5 cells and transfer the cells to a 600 cm2</su...

<ol>
	<li>Knipe, D. M., Howley, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Fields virology. , (2013).</li><li>Engel, E. A., Song, R., Koyuncu, O. O., Enquist, L. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigating+the+biology+of+alpha+herpesviruses+with+MS-based+proteomics.">Investigating the biology of alpha herpesviruses with MS-based proteomics.</a> Proteomics. 15, 1943-1956 (2015).</li><li>Wagner, L. M., DeLuca, N. 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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteomics+of+herpes+simplex+virus+infected+cell+protein+27:+association+with+translation+initiation+factors.">Proteomics of herpes simplex virus infected cell protein 27: association with translation initiation factors.</a> Virology. 330, 487-492 (2004).</li><li>Greco, T. M., Diner, B. A., Cristea, I. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Impact+of+Mass+Spectrometry-Based+Proteomics+on+Fundamental+Discoveries+in+Virology.">The Impact of Mass Spectrometry-Based Proteomics on Fundamental Discoveries in Virology.</a> Annu Rev Virol. 1, 581-604 (2014).</li><li>Conwell, S. E., White, A. E., Harper, J. W., Knipe, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+TRIM27+as+a+novel+degradation+target+of+herpes+simplex+virus+1+ICP0.">Identification of TRIM27 as a novel degradation target of herpes simplex virus 1 ICP0.</a> J Virol. 89, 220-229 (2015).</li><li>Suk, H., Knipe, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteomic+analysis+of+the+herpes+simplex+virus+1+virion+protein+16+transactivator+protein+in+infected+cells.">Proteomic analysis of the herpes simplex virus 1 virion protein 16 transactivator protein in infected cells.</a> Proteomics. 15, 1957-1967 (2015).</li><li>Balasubramanian, N., Bai, P., Buchek, G., Korza, G., Weller, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physical+interaction+between+the+herpes+simplex+virus+type+1+exonuclease,+UL12,+and+the+DNA+double-strand+break-sensing+MRN+complex.">Physical interaction between the herpes simplex virus type 1 exonuclease, UL12, and the DNA double-strand break-sensing MRN complex.</a> J Virol. 84, 12504-12514 (2010).</li><li>Sampath, P., Deluca, N. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Binding+of+ICP4,+TATA-binding+protein,+and+RNA+polymerase+II+to+herpes+simplex+virus+type+1+immediate-early,+early,+and+late+promoters+in+virus-infected+cells.">Binding of ICP4, TATA-binding protein, and RNA polymerase II to herpes simplex virus type 1 immediate-early, early, and late promoters in virus-infected cells.</a> J Virol. 82, 2339-2349 (2008).</li><li>Amelio, A. L., McAnany, P. K., Bloom, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+chromatin+insulator-like+element+in+the+herpes+simplex+virus+type+1+latency-associated+transcript+region+binds+CCCTC-binding+factor+and+displays+enhancer-blocking+and+silencing+activities.">A chromatin insulator-like element in the herpes simplex virus type 1 latency-associated transcript region binds CCCTC-binding factor and displays enhancer-blocking and silencing activities.</a> J Virol. 80, 2358-2368 (2006).</li><li>Cliffe, A. R., Knipe, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Herpes+simplex+virus+ICP0+promotes+both+histone+removal+and+acetylation+on+viral+DNA+during+lytic+infection.">Herpes simplex virus ICP0 promotes both histone removal and acetylation on viral DNA during lytic infection.</a> J Virol. 82, 12030-12038 (2008).</li><li>Herrera, F. J., Triezenberg, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=VP16-dependent+association+of+chromatin-modifying+coactivators+and+underrepresentation+of+histones+at+immediate-early+gene+promoters+during+herpes+simplex+virus+infection.">VP16-dependent association of chromatin-modifying coactivators and underrepresentation of histones at immediate-early gene promoters during herpes simplex virus infection.</a> J Virol. 78, 9689-9696 (2004).</li><li>Kent, J. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=During+lytic+infection+herpes+simplex+virus+type+1+is+associated+with+histones+bearing+modifications+that+correlate+with+active+transcription.">During lytic infection herpes simplex virus type 1 is associated with histones bearing modifications that correlate with active transcription.</a> J Virol. 78, 10178-10186 (2004).</li><li>Oh, J., Fraser, N. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temporal+association+of+the+herpes+simplex+virus+genome+with+histone+proteins+during+a+lytic+infection.">Temporal association of the herpes simplex virus genome with histone proteins during a lytic infection.</a> J Virol. 82, 3530-3537 (2008).</li><li>Catez, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HSV-1+genome+subnuclear+positioning+and+associations+with+host-cell+PML-NBs+and+centromeres+regulate+LAT+locus+transcription+during+latency+in+neurons.">HSV-1 genome subnuclear positioning and associations with host-cell PML-NBs and centromeres regulate LAT locus transcription during latency in neurons.</a> PLoS Pathog. 8, e1002852 (2012).</li><li>Everett, R. D., Murray, J., Orr, A., Preston, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Herpes+simplex+virus+type+1+genomes+are+associated+with+ND10+nuclear+substructures+in+quiescently+infected+human+fibroblasts.">Herpes simplex virus type 1 genomes are associated with ND10 nuclear substructures in quiescently infected human fibroblasts.</a> J Virol. 81, 10991-11004 (2007).</li><li>Tang, Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+minimum+herpes+simplex+virus+type+1+components+necessary+to+localize+transcriptionally+active+DNA+to+ND10.">Determination of minimum herpes simplex virus type 1 components necessary to localize transcriptionally active DNA to ND10.</a> J Virol. 77, 5821-5828 (2003).</li><li>Ishov, A. M., Maul, G. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+periphery+of+nuclear+domain+10+(ND10)+as+site+of+DNA+virus+deposition.">The periphery of nuclear domain 10 (ND10) as site of DNA virus deposition.</a> J Cell Biol. 134, 815-826 (1996).</li><li>Maroui, M. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Latency+Entry+of+Herpes+Simplex+Virus+1+Is+Determined+by+the+Interaction+of+Its+Genome+with+the+Nuclear+Environment.">Latency Entry of Herpes Simplex Virus 1 Is Determined by the Interaction of Its Genome with the Nuclear Environment.</a> PLoS Pathog. 12, e1005834 (2016).</li><li>Sirbu, B. M., Couch, F. B., Cortez, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monitoring+the+spatiotemporal+dynamics+of+proteins+at+replication+forks+and+in+assembled+chromatin+using+isolation+of+proteins+on+nascent+DNA.">Monitoring the spatiotemporal dynamics of proteins at replication forks and in assembled chromatin using isolation of proteins on nascent DNA.</a> Nat Protoc. 7, 594-605 (2012).</li><li>Leung, K. H., Abou El Hassan, M., Bremner, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+rapid+and+efficient+method+to+purify+proteins+at+replication+forks+under+native+conditions.">A rapid and efficient method to purify proteins at replication forks under native conditions.</a> BioTechniques. 55, 204-206 (2013).</li><li>Hobbs, W. E., DeLuca, N. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Perturbation+of+cell+cycle+progression+and+cellular+gene+expression+as+a+function+of+herpes+simplex+virus+ICP0.">Perturbation of cell cycle progression and cellular gene expression as a function of herpes simplex virus ICP0.</a> J Virol. 73, 8245-8255 (1999).</li><li>Lomonte, P., Everett, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Herpes+simplex+virus+type+1+immediate-early+protein+Vmw110+inhibits+progression+of+cells+through+mitosis+and+from+G(1)+into+S+phase+of+the+cell+cycle.">Herpes simplex virus type 1 immediate-early protein Vmw110 inhibits progression of cells through mitosis and from G(1) into S phase of the cell cycle.</a> J Virol. 73, 9456-9467 (1999).</li><li>Dembowski, J. A., DeLuca, N. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+recruitment+of+nuclear+factors+to+productively+replicating+herpes+simplex+virus+genomes.">Selective recruitment of nuclear factors to productively replicating herpes simplex virus genomes.</a> PLoS Pathog. 11, e1004939 (2015).</li><li>Dembowski, J. A., Dremel, S. E., DeLuca, N. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Replication-Coupled+Recruitment+of+Viral+and+Cellular+Factors+to+Herpes+Simplex+Virus+Type+1+Replication+Forks+for+the+Maintenance+and+Expression+of+Viral+Genomes.">Replication-Coupled Recruitment of Viral and Cellular Factors to Herpes Simplex Virus Type 1 Replication Forks for the Maintenance and Expression of Viral Genomes.</a> PLoS Pathog. 13, e1006166 (2017).</li><li>Bjornberg, O., Nyman, P. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+dUTPases+from+herpes+simplex+virus+type+1+and+mouse+mammary+tumour+virus+are+less+specific+than+the+Escherichia+coli+enzyme.">The dUTPases from herpes simplex virus type 1 and mouse mammary tumour virus are less specific than the Escherichia coli enzyme.</a> J Gen Virol. 77 (Pt 12), 3107-3111 (1996).</li><li>Chiou, S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DNA-+and+protein-scission+activities+of+ascorbate+in+the+presence+of+copper+ion+and+a+copper-peptide+complex.">DNA- and protein-scission activities of ascorbate in the presence of copper ion and a copper-peptide complex.</a> J Biochem. 94, 1259-1267 (1983).</li><li>Kennedy, D. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+consequences+of+copper+complexes+used+to+catalyze+bioorthogonal+click+reactions.">Cellular consequences of copper complexes used to catalyze bioorthogonal click reactions.</a> J Am Chem Soc. 133, 17993-18001 (2011).</li><li>Snel, B., Lehmann, G., Bork, P., Huynen, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=STRING:+a+web-server+to+retrieve+and+display+the+repeatedly+occurring+neighbourhood+of+a+gene.">STRING: a web-server to retrieve and display the repeatedly occurring neighbourhood of a gene.</a> Nucleic Acids Res. 28, 3442-3444 (2000).</li></ol>

This protocol includes multiple steps which, if not followed carefully, can result in significantly reduced protein yield or contamination with cellular DNA. It is critical that stationary cells are used for all experiments to ensure that cellular DNA is not labeled and purified. This can be confirmed by the absence of cellular DNA polymerases in the protein sample because HSV-1 does not utilize cellular DNA polymerase for genome synthesis. During EdC labeling and nuclei harvesting steps, samples should be staggered to e...

Viruses have a limited capacity to carry out essential functions and therefore depend on host factors to facilitate critical aspects of infection including viral gene expression, replication, repair, recombination, and transport. The activities of these host factors are often augmented by virally encoded proteins. In addition, viruses must avoid detection and interference by cellular responses to viral infection. Therefore, virus host interactions dictate the outcome of infection. Of paramount importance is understanding how viruses alter the cellular environment to adapt the cellular machinery to facilitate viral processes. Of particular interest is identifying which factors and processes act on viral genomes throughout the infectious cycle.
Herpes simplex virus type 1 (HSV-1) is a double stranded DNA virus that infects a substantial proportion of the human population. Within the first hour of infection, the viral genome enters the nucleus, where an ordered cascade of viral gene expression ensues in coordination with viral DNA (vDNA) replication1. In the nucleus, genomes are subject to epigenetic regulation, undergo repair and recombination, and are packaged into capsids, such that the first progeny virions are produced within less than six hours. The comprehensive evaluation of viral genome associated proteins throughout the course of infection will lay the groundwork to investigate the molecular details of processes that act on viral genomes, and will provide insight into which viral and cellular factors are involved in various stages of infection.
Previous methods for the investigation of host factors involved in viral infection include affinity purification of viral proteins for the analysis of associated cellular proteins2,3,4,5,6,7,8,9. These assays have been instrumental for the identification of cellular factors involved in host antiviral responses, as well as viral chromatin modification, gene expression, and DNA repair. However, it is difficult to ascertain whether interactions depend on the association with vDNA, and proteomics only provide insight into interactions that occur as a function of a specific viral factor. Chromatin immunoprecipitation (ChIP) has been used to identify where specific viral and cellular proteins bind to viral genomes10,11,12,13,14,15 and fluorescent in situ hybridization (FISH) combined with immunocytochemistry has enabled the visualization of cellular factors that colocalize with vDNA16,17,18,19,20. These assays allow for spatial and temporal analysis. However, limitations include the need for highly specific antibodies, limited sensitivity, and the need for previous insight into virus host interactions. We therefore developed a method based on iPOND (isolation of proteins on nascent DNA)21 and aniPOND (accelerated native iPOND)22 to selectively label and purify vDNA from infected cells for the unbiased identification of viral genome associated proteins by mass spectrometry. iPOND has been instrumental for the investigation of cellular replication fork dynamics.
For the selective purification of viral genomes from infected cells, replicating vDNA is labeled with ethynyl modified nucleosides, 5-ethynyl-2&#180;-deoxyuridine (EdU) or 5-ethynyl-2&#180;-deoxycytidine (EdC) (Figure 1), followed by covalent conjugation to biotin azide via click chemistry to facilitate single step purification of viral genomes and associated proteins on streptavidin-coated beads (Figure 2B). Importantly, infections are carried out in stationary cells, which are not engaged in cellular DNA replication to enable specific labeling of vDNA. Furthermore, HSV-1 infection causes cell cycle arrest and inhibits cellular DNA replication23,24. Virus can be prelabeled before infection for the analysis of proteins associated with incoming viral genomes (Figure 1A) or labeled during DNA replication for the analysis of proteins associated with newly synthesized vDNA (Figure 1B)25. Furthermore, pulse chase analysis can be used to investigate the nature of proteins associated with viral replication forks (Figure 1C)26. In addition, ethynyl-modified vDNA can be covalently conjugated to a fluorophore for spatial investigation of protein dynamics (Figure 2A and Figure 3). Imaging allows for the direct visualization of vDNA and is a complimentary approach for the validation of vDNA-protein interactions, and can be adapted to track viral genomes throughout infection. We anticipate that these approaches could be further modified to study any aspect of herpesviral infection, including latency and reactivation, and to study other DNA viruses. Moreover, labeling with 5-ethynyl uridine (EU) could allow for the analysis of RNA viral genomes.

<table border="0" cellpadding="0" cellspacing="0" width="1930">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">MRC-5 cells</td>
			<td style="width:197px;">ATCC</td>
			<td style="width:101px;">CCL-171</td>
			<td style="width:1215px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Fetal Bovine Serum (FBS)</td>
			<td style="width:197px;">Gibco</td>
			<td style="width:101px;">26140-179</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Dulbecco&#39;s Modified Eagle Medium (DMEM)</td>
			<td style="width:197px;">Gibco</td>
			<td style="width:101px;">12800-082</td>
			<td>substituted with 10% FBS, 2 mM L-glutamine, 12 mM&#160; (for growth in flasks) or 30 mM (for growth in dishes) sodium-bicarbinate</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:419px;">600 cm2 tissue culture dish</td>
			<td style="width:197px;">Thermo Fisher Scientific</td>
			<td align="right" style="width:101px;">166508</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Tris Buffered Saline (TBS), pH 7.4</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td>137 mM NaCl, 5 mM KCl, 491 mM MgCl, 680 mM CaCl, 25.1 mM Tricine</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:419px;">HSV-1 stock</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td>stocks with titers greater than 1x109 PFU/mL work best</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Sephadex G-25&#160; column (PD-10 Desalting Column)</td>
			<td style="width:197px;">GE Healthcare</td>
			<td align="right" style="width:101px;">17085101</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Dimethyl sulfoxide (DMSO)</td>
			<td style="width:197px;">Fisher Scientific</td>
			<td style="width:101px;">D128-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">5&#180;-Ethynyl-2&#180;-deoxycytidine (EdC)</td>
			<td style="width:197px;">Sigma-Aldrich</td>
			<td style="width:101px;">T511307</td>
			<td>Dissolve in DMSO to prepare 40 mM stock, aliquot, and store at -20 &#176;C&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">2&#180;-deoxycytidine (deoxyC)</td>
			<td style="width:197px;">Sigma-Aldrich</td>
			<td style="width:101px;">D3897</td>
			<td>Dissolve in water to prepare 40 mM stock, aliquot, and store at -20 &#176;C&#160;</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:419px;">Nuclear Extraction Buffer (NEB)</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td>prepare fresh (20 mM Hepes pH 7.2, 50 mM NaCl, 3 mM MgCl2, 300 mM Sucrose, 0.5% Igepal)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Cell scraper</td>
			<td style="width:197px;">Bellco glass</td>
			<td style="width:101px;">7731-22000</td>
			<td>Autoclave before use</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Trypan blue solution</td>
			<td style="width:197px;">Sigma-Aldrich</td>
			<td style="width:101px;">T8154</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:419px;">PBS, pH 7.2 (10x)</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td>1.37 M NaCl, 27 mM KCl, 100 mM Na2HPO4, 18 mM KH2PO4 (dilute to 1x in sterile water before use)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Copper (II) sulfate pentahydrate (CuSO4-5H2O)</td>
			<td style="width:197px;">Fisher Scientific</td>
			<td style="width:101px;">C489</td>
			<td>Prepare 100 mM stock and store at 4 &#176;C for up to 1 month</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">(+) Sodium L-ascorbate</td>
			<td style="width:197px;">Sigma-Aldrich</td>
			<td style="width:101px;">A4034</td>
			<td>Freshly prepare 100 mM stock and store on ice until use</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Biotin azide</td>
			<td style="width:197px;">Invitrogen</td>
			<td style="width:101px;">B10184</td>
			<td>Prepare 10 mM stock in DMSO, aliquot, and store at -20 &#176;C for up to 1 year&#160;</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:419px;">Click Reaction Mix</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td>prepare immediately before use by adding reagents in the indicated order (10 mL: 8.8 mL 1x PBS, 200 mL 100 mM CuSO4, 25mL 10 mM Biotin Azide, 1 mL 100 mM sodium ascorbate)&#160;&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">cOmplete Protease Inhibitor Cocktail</td>
			<td style="width:197px;">Roche</td>
			<td align="right" style="width:101px;">11697498001</td>
			<td>Dissolve in 1 mL water to prepare 50x stock, can store at 4 &#176;C for up to 1 week, or directly add 1 pill to 50 mL buffer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">freezing buffer</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td>prepare fresh (7 mL 100% glycerol, 3 mL NEB, 200 &#956;L 50x protease inhibitor)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Buffer B1</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td>prepare fresh (25 mM NaCl, 2 mM EDTA, 50 mM Tris-HCl pH 8, 1% Igepal, 1x protease inhibitor)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Buffer B2</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td>prepare fresh (150 mM NaCl, 2 mM EDTA, 50 mM Tris-HCl pH 8, 0.5% Igepal, 1x protease inhibitor)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Buffer B3</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td>prepare fresh (150 mM NaCl, 2 mM EDTA, 50 mM Tris-HCl pH 8, 1x protease inhibitor)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Vibra Cell Ultra Sonic Processer equipped with a 3 mm microtip probe</td>
			<td style="width:197px;">Sonics</td>
			<td style="width:101px;">VCX 130</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Cell strainer</td>
			<td style="width:197px;">Falcon</td>
			<td align="right" style="width:101px;">352360</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Dynabeads MyOne Streptavidin T1</td>
			<td style="width:197px;">Life Technologies</td>
			<td align="right" style="width:101px;">65601</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">DynaMag-2 Magnet</td>
			<td style="width:197px;">Life Technologies</td>
			<td style="width:101px;">12321D</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Mini-Tube Rotator</td>
			<td style="width:197px;">Fisher Scientific</td>
			<td style="width:101px;">260750F</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">2X Laemmli sample buffer</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td>Mix 400 mg of SDS, 2 mL 100% glycerol, 1.25 mL of 1 M Tris (pH 6.8), and 10 mg of bromophenol blue in 8 mL water. Store at 4&#160; &#176;C for up to 6 months. Before use add 1 M DTT to a final concentration of 200 mM.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">cap locks for 1.5 mL tube</td>
			<td style="width:197px;">Fisher Scientific</td>
			<td style="width:101px;">NC9679153</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Standard western blotting reagents</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">NOVEX Colloidal Blue Staining Kit</td>
			<td style="width:197px;">Invitrogen</td>
			<td style="width:101px;">LC6025</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">12-well tissue culture dish</td>
			<td style="width:197px;">Corning</td>
			<td align="right" style="width:101px;">3513</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Coverslips</td>
			<td style="width:197px;">Fisher Scientific</td>
			<td style="width:101px;">12-545-100</td>
			<td>Autoclave before use</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Microscope slides</td>
			<td style="width:197px;">Fisher Scientific</td>
			<td style="width:101px;">12-552-5</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:419px;">16% paraformaldehyde</td>
			<td style="width:197px;">Electron Microscopy Sciences</td>
			<td align="right" style="width:101px;">15710</td>
			<td>dilute to 3.7% in 1x PBS before use</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Bovine serum albumin (BSA)</td>
			<td style="width:197px;">Fisher Scientific</td>
			<td style="width:101px;">BP1605</td>
			<td>prepare 3% in 1x PBS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Permeabilization buffer (0.5% Triton-X 100)</td>
			<td style="width:197px;">Sigma-Aldrich</td>
			<td style="width:101px;">T8787</td>
			<td>prepare 0.5% Triton-X 100 in 1x PBS</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:419px;">Click reaction cocktail - Click-iT EdU Alexa Fluor 488 Imaging Kit</td>
			<td style="width:197px;">Molecular Probes</td>
			<td style="width:101px;">C10337</td>
			<td>prepare according to manufactorer&#39;s protocol</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Hoechst 33342</td>
			<td style="width:197px;">Life Technologies</td>
			<td style="width:101px;">H1399</td>
			<td>prepare 10 mg/mL in water, can store at 4 &#176;C for up to 1 year</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">mouse anti-ICP8 primary antibody</td>
			<td style="width:197px;">Abcam</td>
			<td style="width:101px;">ab20194</td>
			<td>Use a 1:200 dilution in 1x PBS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">mouse anti-UL42 primary antibody (2H4)</td>
			<td style="width:197px;">Abcam</td>
			<td style="width:101px;">ab19311</td>
			<td>Use a 1:200 dilution in 1x PBS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Goat anti-mouse 594-conjugated secondary antibody</td>
			<td style="width:197px;">Life Technologies</td>
			<td style="width:101px;">a11005</td>
			<td>Use a 1:500 dilution in 1x PBS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Immu-mount</td>
			<td style="width:197px;">Thermo Fisher Scientific</td>
			<td align="right" style="width:101px;">9990402</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">2x SDS-bicarb solution</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td>2% SDS, 200 mM NaHCO3</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Phenol:chloroform:isoamyl alcohol</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td>mix 25:24:1 at least 1 day before use, store at 4 &#176;C in the dark</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">chloroform:isoamyl alcohol</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td>mix 24:1 at least 1 day before use, store at room temperature in the dark</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">10x Tris EDTA (TE), pH 8.0</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td>100 mM Tris, 10 mM EDTA (dilute to 1x before use)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Qiaquick PCR purification kit</td>
			<td style="width:197px;">Qiagen</td>
			<td align="right" style="width:101px;">28104</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">3 M sodium acetate pH 5.2</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Qubit 2.0 Fluorometer</td>
			<td style="width:197px;">Invitrogen</td>
			<td style="width:101px;">Q32866</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Qubit dsDNA HS Assay Kit</td>
			<td style="width:197px;">Invitrogen</td>
			<td style="width:101px;">Q32851</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Qubit assay tubes</td>
			<td style="width:197px;">Invitrogen</td>
			<td style="width:101px;">Q32856</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Fluorescence microscope equipped with imaging software</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Microcentrifuge for 1.5 mL tubes</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Tabletop centrifuge for 15 and 50 mL tubes</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Cell culture incubator</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Biosafety cabinet</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:419px;">Heat blocks</td>
			<td style="width:197px;"></td>
			<td style="width:101px;"></td>
			<td>65 &#176;C and 95 &#176;C</td>
		</tr>
	</tbody>
</table>

purification of viral dna for the identification of associated viral and cellular proteins

The goal of this protocol is to isolate herpes simplex virus type 1 (HSV-1) DNA from infected cells for the identification of associated viral and cellular proteins by mass spectrometry. Although proteins that interact with viral genomes play major roles in determining the outcome of infection, a comprehensive analysis of viral genome associated proteins was not previously feasible. Here we demonstrate a method that enables the direct purification of HSV-1 genomes from infected cells. Replicating viral DNA is selectively labeled with modified nucleotides that contain an alkyne functional group. Labeled DNA is then specifically and irreversibly tagged via the covalent attachment of biotin azide via a copper(I)-catalyzed azide-alkyne cycloaddition or click reaction. Biotin-tagged DNA is purified on streptavidin-coated beads and associated proteins are eluted and identified by mass spectrometry. This method enables the selective targeting and isolation of HSV-1 replication forks or whole genomes from complex biological environments. Furthermore, adaptation of this approach will allow for the investigation of various aspects of herpesviral infection, as well as the examination of the genomes of other DNA viruses.

The use of click chemistry for the purification of DNA from cells was first accomplished by the iPOND method21. The purpose of iPOND is to purify cellular replication forks for the identification of associated proteins. We have adapted this technique to specifically study vDNA protein interactions during infection. Manipulation of the approach to label viral genomes with EdC (Figure 1), combined with synchronized infections, has allowe...

Watch this Scientific Journal Video about Purification of Viral DNA for the Identification of Associated Viral and Cellular Proteins at JoVE.com

Purification of Viral DNA for the Identification of Associated Viral and Cellular Proteins

The goal of this protocol is to specifically tag and selectively isolate viral DNA from infected cells for the characterization of viral genome associated proteins.

The goal of this protocol is to isolate herpes simplex virus type 1 (HSV-1) DNA from infected cells for the identification of associated viral and ...

The overall goal of this method is to purify Herpes Simplex virus type one DNA from infected cells for the proteomic analysis of viral genome associated proteins. This method provides key insights into the involvement of cellular factors and Herpes virus infection. The main advantage of this technique is that it can be adapted to directly purify different populations of viral DNA from infected cells, allowing for the analysis of multiple aspects of infection.Begin this procedure with culturing of MRC five cells as described in the text protocol. Then, dilute HSV-1 in cold tris-buffered saline or TBS. For the following steps, it is important to turn off the blower and the tissue culture hood to prevent cells from drying out.Use a pipette to transfer the growth medium from the MRC 5 cells to a sterile bottle to add back to the cells after infection. Infect the cells by adding seven milliliters of diluted virus to the cells. Rock the cells every 10 minutes for one hour at room temperature.Following absorption, aspirate the innoculum, rinse the cells with 50 milliliters of room temperature TBS and replace the original growth medium. Then, incubate the cells at 37 degrees celsius in the presence of 5%carbon dioxide. After the onset of viral DNA replication, around four hours post infection, label replicating viral DNA.To do so, dilute EdC in one milliliter of growth medium and add it to the cell culture medium of infected cells for two to four hours. To harvest nuclei, replace the growth medium with 20 milliliters of nuclei extraction buffer and incubate for 20 minutes at four degree celsius with occasional rocking. After incubation, scrape nuclei from the plate using a cell scraper and transfer them to a 50 milliliter conical tube on ice.Centrifuge for 10 minutes at 2, 500 x g and four degree celsius to pellet the nuclei. Following centrifugation, discard the supernatant. Gently dislodge the nuclear pellet in 10 milliliters of phosphate buffer saline or PBS and transfer it to a 50 milliliter conical tube.Then, centrifuge the sample as before. After completely removing the PBS, re-suspend the nuclear pellet in 10 milliliters of click reaction mix, by gently pipetting up and down five times with a 10 milliliter pipette. Rotate the sample for one hour at four degree celsius, before pelleting the nuclei as before.Completely remove the quick reaction mix, then, wash the pellet by gently re-suspending it in 10 milliliters of PBS and centrifuging again. Now, carefully re-suspend the nuclear pellet in one milliliter PBS and transfer the solution to a 1.5 milliliter microcentrifuge tube. Following centrifugation, completely remove the PBS and flash freeze the pellet in liquid nitrogen.At this point, the pellet can be stored at 80 degree celsius or the procedure can be continued. To lyse the nuclei and fragment the DNA, re-suspend the thawed nuclei in 500 microliters of Buffer B1 by pipetting up and down. Incubate the suspension on ice for 45 minutes.Then, sonicate the samples six times for 30 seconds each at 40%amplitude, using a three millimeter microtip probe. Place the samples on ice for at least 30 seconds between pulses. After sonication, samples should appear clear, not cloudy.Pellet the cell debris by centrifuging at 14, 000 x G for 10 minutes at four degrees celsius. The pellet size should decrease substantially, filter the supernatant through a 100 micron cell strainer and retain the flow through. Then, add 500 microliters of Buffer B2 to the filtered supernatant.To bind the biotinylated DNA to streptavidin coated beads, prepare the streptavidin magnetic beads by transferring 300 microliters of bead slurry to a 1.5 milliliter microcentrifuge tube. Prepare one tube of beads per sample. Wash the beads three times with milliliter of Buffer B2 by vortexing to re-suspend, applying to a magnet to separate the beads and aspirating the wash buffer.Then, add 900 microliters of the sample to the washed beads. The remainder of the sample will be used for input DNA and protein isolation. Rotate the suspension overnight at four degree celsius.The next day, place the samples into a magnetic microfuge tube rack and remove the supernatant. Gently re-suspend the beads in one milliliter of Buffer B2, before rotating at four degree celsius for five minutes. Remove the supernatant again using the magnetic microfuge tube rack.This time, gently re-suspend the beads in one milliliter Buffer B3 and rotate at four degree celsius for five minutes. After removing the supernatant from the bead mixture using the magnet, re-suspend the beads in 50 microliters of 2x Laemmli sample buffer to allude DNA protein complexes. Next, boil the samples at 95 degrees celsius for 15 minutes.Vortex a mix before quickly spinning the samples in a microfuge. Apply the samples to the magnet and transfer the allot to a new tube. Finally, flash freeze the samples and store them at 80 degrees celsius.Perform protein analysis as described in the text protocol. EdC labeling was carried out for zero, 20, 40 or 60 minutes followed by the purification of viral DNA and associated proteins. The eluted proteins were subject to coomassie blue staining and western blotting with the antibody specific for viral DNA binding proteins, ICP4 and UL42.The arrow indicates streptavidin that was stripped from the beads during elution which is present under all conditions. Proteins isolated by this method are then subject to mass spectrometry. The pie chart illustrates the number of proteins in each functional category that were found to be associated with Herpes Simplex virus type on genomes at six hours post infection.A closer look at protein-protein interactions amongst identified proteins was carried out using the string functional protein association network database. The results reveal sub-complexes of proteins that function together in the same biological process. After watching this video, you should have a good understanding of how to purify viral DNA from infected cells for the proteomic investigation of viral genome associated proteins.This technique can be completed in three to four days. While attempting this procedure, it is important to remember to take precautions to prevent DNAse or protease contamination of samples. In addition to this procedure, other methods like immunofluorescence can be performed to verify the nature of EdC labeled viral DNA.This technique has paved the way for researchers in the field of Herpes virology, to explore the functions of host proteins and viral infection.

purification-viral-dna-for-identification-associated-viral-cellular

Research

JoVE Journal

Immunology and Infection

Using a Pan-Viral Microarray Assay (Virochip) to Screen Clinical Samples for Viral Pathogens

The diagnosis of viral causes of many infectious diseases is difficult due to the inherent sequence diversity of viruses as well as the ongoing emergence of novel viral pathogens, such as SARS coronavirus and 2009 pandemic H1N1 influenza virus, that are not detectable by traditional methods. To address these challenges, we have previously developed and validated a pan-viral microarray platform called the Virochip with the capacity to detect all known viruses as well as novel variants on the basis of conserved sequence homology1. Using the Virochip, we have identified the full spectrum of viruses associated with respiratory infections, including cases of unexplained critical illness in hospitalized patients, with a sensitivity equivalent to or superior to conventional clinical testing2-5. The Virochip has also been used to identify novel viruses, including the SARS coronavirus6,7, a novel rhinovirus clade5, XMRV (a retrovirus linked to prostate cancer)8, avian bornavirus (the cause of a wasting disease in parrots)9, and a novel cardiovirus in children with respiratory and diarrheal illness10. The current version of the Virochip has been ported to an Agilent microarray platform and consists of ~36,000 probes derived from over ~1,500 viruses in GenBank as of December of 2009. Here we demonstrate the steps involved in processing a Virochip assay from start to finish (~24 hour turnaround time), including sample nucleic acid extraction, PCR amplification using random primers, fluorescent dye incorporation, and microarray hybridization, scanning, and analysis.

Using a Pan-Viral Microarray Assay Virochip to Screen Clinical Samples for Viral Pathogens

The Virochip is a pan-viral microarray designed to simultaneously detect all known viruses as well as novel viruses on the basis of conserved sequence homology. Here we demonstrate how to run a Virochip assay to analyze clinical samples for the presence of both known and unknown viruses.

The diagnosis of viral causes of many infectious diseases is difficult due to the inherent sequence diversity of viruses as well as the ongoing emergence ...

Isolation of Fidelity Variants of RNA Viruses and Characterization of Virus Mutation Frequency

RNA viruses use RNA dependent RNA polymerases to replicate their genomes. The intrinsically high error rate of these enzymes is a large contributor to the generation of extreme population diversity that facilitates virus adaptation and evolution. Increasing evidence shows that the intrinsic error rates, and the resulting mutation frequencies, of RNA viruses can be modulated by subtle amino acid changes to the viral polymerase. Although biochemical assays exist for some viral RNA polymerases that permit quantitative measure of incorporation fidelity, here we describe a simple method of measuring mutation frequencies of RNA viruses that has proven to be as accurate as biochemical approaches in identifying fidelity altering mutations. The approach uses conventional virological and sequencing techniques that can be performed in most biology laboratories. Based on our experience with a number of different viruses, we have identified the key steps that must be optimized to increase the likelihood of isolating fidelity variants and generating data of statistical significance. The isolation and characterization of fidelity altering mutations can provide new insights into polymerase structure and function1-3. Furthermore, these fidelity variants can be useful tools in characterizing mechanisms of virus adaptation and evolution4-7.

The present article describes the steps required to isolate and characterize RNA polymerase fidelity variants of RNA viruses and how to use mutation frequency data to confirm fidelity changes in tissue culture.

RNA viruses use RNA dependent RNA polymerases to replicate their genomes. The intrinsically high error rate of these enzymes is a large contributor to the ...

Separation of Single-stranded DNA, Double-stranded DNA and RNA from an Environmental Viral Community Using Hydroxyapatite Chromatography

Viruses, particularly bacteriophages (phages), are the most numerous biological entities on Earth1,2. Viruses modulate host cell abundance and diversity, contribute to the cycling of nutrients, alter host cell phenotype, and influence the evolution of both host cell and viral communities through the lateral transfer of genes 3. Numerous studies have highlighted the staggering genetic diversity of viruses and their functional potential in a variety of natural environments. 
Metagenomic techniques have been used to study the taxonomic diversity and functional potential of complex viral assemblages whose members contain single-stranded DNA (ssDNA), double-stranded DNA (dsDNA) and RNA genotypes 4-9. Current library construction protocols used to study environmental DNA-containing or RNA-containing viruses require an initial nuclease treatment in order to remove nontargeted templates 10. However, a comprehensive understanding of the collective gene complement of the virus community and virus diversity requires knowledge of all members regardless of genome composition. Fractionation of purified nucleic acid subtypes provides an effective mechanism by which to study viral assemblages without sacrificing a subset of the community&#x2019;s genetic signature. 
Hydroxyapatite, a crystalline form of calcium phosphate, has been employed in the separation of nucleic acids, as well as proteins and microbes, since the 1960s11. By exploiting the charge interaction between the positively-charged Ca2+ ions of the hydroxyapatite and the negatively charged phosphate backbone of the nucleic acid subtypes, it is possible to preferentially elute each nucleic acid subtype independent of the others. We recently employed this strategy to independently fractionate the genomes of ssDNA, dsDNA and RNA-containing viruses in preparation of DNA sequencing 12. Here, we present a method for the fractionation and recovery of ssDNA, dsDNA and RNA viral nucleic acids from mixed viral assemblages using hydroxyapatite chromotography.

We describe an efficient method to separate single-stranded DNA, double-stranded DNA and RNA molecules from environmental viral communities. Nucleic acids are fractionated using hydroxyapatite chromatography with increasing concentrations of phosphate-containing buffers. This method permits the isolation of all viral nucleic acid types from environmental samples.

Viruses, particularly bacteriophages (phages), are the most numerous biological entities on Earth1,2.  Viruses modulate host cell abundance and diversity, ...

Preparation of Viral DNA from Nucleocapsids

Viruses are obligate cellular parasites, and thus the study of their DNA requires isolating viral material away from host cell contaminants and DNA. Several downstream applications require large quantities of pure viral DNA, which is provided by this protocol. These applications include viral genome sequencing, where the removal of host DNA is crucial to optimize data output for viral sequences, and the production of new viral recombinant strains, where co-transfection of purified plasmid and linear viral DNA facilitates recombination.1,2,3 
This procedure utilizes a combination of extractions and density-based centrifugation to isolate purified linear herpesvirus nucleocapsid DNA from infected cells.4,5 The initial purification steps aim to isolate purified viral capsids, which contain and protect the viral DNA during the extractions and centrifugation steps that remove cellular proteins and DNA. Lysis of nucleocapsids then releases viral DNA, and two final phenol-chloroform steps remove remaining proteins. The final DNA captured from solution is highly concentrated and pure, with an average OD260/280 of 1.90. Depending on the quantity of infected cells used, yields of viral DNA range from 150-800 &mu;g or more. The purity of this DNA makes it stable during long-term storage at 4C. This DNA is thus ideally suited for high-throughput sequencing, high fidelity PCR reactions, and transfections. 
Prior to beginning the protocol, it is important to know the average number of cells per dish (e.g. an average of 8 x 106 PK-15 cells in a confluent 15 cm dish), and the titer of the viral stock to be used (e.g. 1 x 108 plaque-forming units per ml). These are necessary to calculate the appropriate multiplicity of infection (MOI) for the protocol.6 For instance, to infect one 15 cm dish of PK-15 cells with the above viral stock, at an MOI of 5, you would use 400 &mu;l of viral stock and dilute it with 3.6 ml of medium (total inoculation volume of 4 ml for one 15 cm plate).
Multiple viral DNA preparations can be prepared at the same time. The number of simultaneous preparations is limited only by the number of tubes held by the ultracentrifuge rotor (one per virus; see step 3.9 below). Here we describe the procedure as though being done for one virus.

We describe the process of isolating high purity herpesvirus nucleocapsid DNA from infected cells. The final DNA captured from solution is of high concentration and purity, making it ideally suited for high-throughput sequencing, high fidelity PCR reactions, and transfections to produce new viral recombinants.

Viruses are obligate cellular parasites, and thus the study of their DNA requires isolating viral material away from host cell contaminants and DNA. ...

Production and Titering of Recombinant Adeno-associated Viral Vectors

In recent years recombinant adeno-associated viral vectors (AAV) have become increasingly valuable for in vivo studies in animals, and are also currently being tested in human clinical trials. Wild-type AAV is a non-pathogenic member of the parvoviridae family and inherently replication-deficient. The broad transduction profile, low immune response as well as the strong and persistent transgene expression achieved with these vectors has made them a popular and versatile tool for in vitro and in vivo gene delivery. rAAVs can be easily and cheaply produced in the laboratory and, based on their favourable safety profile, are generally given a low safety classification. Here, we describe a method for the production and titering of chimeric rAAVs containing the capsid proteins of both AAV1 and AAV2. The use of these so-called chimeric vectors combines the benefits of both parental serotypes such as high titres stocks (AAV1) and purification by affinity chromatography (AAV2). These AAV serotypes are the best studied of all AAV serotypes, and individually have a broad infectivity pattern. The chimeric vectors described here should have the infectious properties of AAV1 and AAV2 and can thus be expected to infect a large range of tissues, including neurons, skeletal muscle, pancreas, kidney among others. The method described here uses heparin column purification, a method believed to give a higher viral titer and cleaner viral preparation than other purification methods, such as centrifugation through a caesium chloride gradient. Additionally, we describe how these vectors can be quickly and easily titered to give accurate reading of the number of infectious particles produced.

Recombinant adeno-associated virus (rAAVs) vectors are becoming increasingly valuable for in vivo studies in animals. We describe how rAAVs can be produced in the laboratory and how these vectors can be titered to give an accurate reading of the number of infectious particles produced.

In recent years recombinant adeno-associated viral vectors (AAV) have become increasingly valuable for in vivo studies in animals, and are also currently ...

A TIRF Microscopy Technique for Real-time, Simultaneous Imaging of the TCR and its Associated Signaling Proteins

Signaling is initiated through the T Cell Receptor (TCR) when it is engaged by antigenic peptide fragments bound by Major Histocompatibility Complex (pMHC) proteins expressed on the surface of antigen presenting cells (APCs). The TCR complex is composed of the ligand binding TCR&alpha;&beta; heterodimer that associates non-covalently with CD3 dimers (the &#949;&delta; and &#949;&gamma; heterodimers and the &zeta;&zeta; homodimer)1. Upon engagement of the receptor, the CD3 &zeta; chains are phosphorylated by the Src family kinase, Lck. This leads to the recruitment of the Syk family kinase, Zap70, which is then phosphorylated and activated by Lck. After that, Zap70 phosphorylates the adapter proteins LAT and SLP76, initiating the formation of the proximal signaling complex containing a large number of different signaling molecules2. 
The formation of this complex eventually results in calcium and Ras-dependent transcription factor activation and the consequent initiation of a complex series of gene expression programs that give rise to T cell differentiation2. TCR signals (and the resulting state of differentiation) are modulated by many other factors, including antigen potency and crosstalk with co-stimulatory/co-inhibitory, chemokine, and cytokine receptors 3-4. Studying the spatial and temporal organization of the proximal signaling complex under various stimulation conditions is, therefore, key to understanding the TCR signaling pathway as well as its regulation by other signaling pathways.
One very useful model system to study signaling initiated by the TCR at the plasma membrane in T cells is glass-supported lipid bilayers, as described previously5-6. They can be utilized to present antigenic pMHC complexes, adhesion, and co-stimulatory molecules to T cells-serving as artificial APCs. By imaging the T cells interacting with the lipid bilayer using total internal reflection fluorescence microscopy (TIRFM), we can restrict the excitation to within 100 nm of the space between the glass and the cell surface 7-8. This allows us to image primarily the signaling events occurring at the plasma membrane. As we are interested in imaging the recruitment of signaling proteins to the TCR complex, we describe a two-camera TIRF imaging system wherein the TCR, labeled with fluorescent Fab (fragment antigen binding) fragments of the H57 antibody (purified from hybridoma H57-597, ATCC, ATCC Number:HB-218) which is specific for TCR&beta;, and signaling proteins, tagged with GFP, may be imaged simultaneously and in real time. This strategy is necessary due to the highly dynamic nature of both the T cells and of the signaling events that are occurring at the TCR. This imaging modality has allowed researchers to image single ligands 9-11 as well as recruitment of signaling molecules to activated receptors and is an excellent system to study biochemistry in-situ12-16.

The compartmentalization of proteins either within the plasma membrane or into intracellular locations is one regulatory mechanism that can greatly influence signaling outcomes; hence, to understand signaling it is important to study the spatial and temporal behavior of the proteins involved. We describe here a TIRF microscopy based system to study signal transduction in T cells, but is broadly applicable.

Signaling is initiated through the T Cell Receptor (TCR) when it is engaged by antigenic peptide fragments bound by Major Histocompatibility Complex ...

Establishing a Liquid-covered Culture of Polarized Human Airway Epithelial Calu-3 Cells to Study Host Cell Response to Respiratory Pathogens In vitro

The apical and basolateral surfaces of airway epithelial cells demonstrate directional responses to pathogen exposure in vivo. Thus, ideal in vitro models for examining cellular responses to respiratory pathogens polarize, forming apical and basolateral surfaces. One such model is differentiated normal human bronchial epithelial cells (NHBE). However, this system requires lung tissue samples, expertise isolating and culturing epithelial cells from tissue, and time to generate an air-liquid interface culture.
Calu-3 cells, derived from a human bronchial adenocarcinoma, are an alternative model for examining the response of proximal airway epithelial cells to respiratory insult1, pharmacological compounds2-6, and bacterial7-9 and viral pathogens, including influenza virus, rhinovirus and severe acute respiratory syndrome - associated coronavirus10-14. Recently, we demonstrated that Calu-3 cells are susceptible to respiratory syncytial virus (RSV) infection in a manner consistent with NHBE15,16 . Here, we detail the establishment of a polarized, liquid-covered culture (LCC) of Calu-3 cells, focusing on the technical details of growing and culturing Calu-3 cells, maintaining cells that have been cultured into LCC, and we present the method for performing respiratory virus infection of polarized Calu-3 cells.
To consistently obtain polarized Calu-3 LCC, Calu-3 cells must be carefully subcultured before culturing in Transwell inserts. Calu-3 monolayer cultures should remain below 90% confluence, should be subcultured fewer than 10 times from frozen stock, and should regularly be supplied with fresh medium. Once cultured in Transwells, Calu-3 LCC must be handled with care. Irregular media changes and mechanical or physical disruption of the cell layers or plates negatively impact polarization for several hours or days. Polarization is monitored by evaluating trans-epithelial electrical resistance (TEER) and is verified by evaluating the passive equilibration of sodium fluorescein between the apical and basolateral compartments17,18 . Once TEER plateaus at or above 1,000 &Omega;&times;cm2, Calu-3 LCC are ready to use to examine cellular responses to respiratory pathogens.

Establishing a Liquid-covered Culture of Polarized Human Airway Epithelial Calu-3 Cells to Study Host Cell Response to Respiratory Pathogens In vitro

The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention.

The  apical and basolateral surfaces of airway epithelial cells demonstrate  directional responses to pathogen exposure in  vivo. Thus, ideal in vitro ...

Phage Phenomics: Physiological Approaches to Characterize Novel Viral Proteins

Current investigations into phage-host interactions are dependent on extrapolating knowledge from (meta)genomes. Interestingly, 60 - 95% of all phage sequences share no homology to current annotated proteins. As a result, a large proportion of phage genes are annotated as hypothetical. This reality heavily affects the annotation of both structural and auxiliary metabolic genes. Here we present phenomic methods designed to capture the physiological response(s) of a selected host during expression of one of these unknown phage genes. Multi-phenotype Assay Plates (MAPs) are used to monitor the diversity of host substrate utilization and subsequent biomass formation, while metabolomics provides bi-product analysis by monitoring metabolite abundance and diversity. Both tools are used simultaneously to provide a phenotypic profile associated with expression of a single putative phage open reading frame (ORF). Representative results for both methods are compared, highlighting the phenotypic profile differences of a host carrying either putative structural or metabolic phage genes. In addition, the visualization techniques and high throughput computational pipelines that facilitated experimental analysis are presented.

Here, we present phenomic approaches for the functional characterization of putative phage genes. Techniques include a developed assay capable of monitoring host anabolic metabolism, the Multi-phenotype Assay Plates (MAPs), in addition to the established method of metabolomics, capable of measuring effects to catabolic metabolism.

Current investigations into phage-host interactions are dependent on extrapolating knowledge from (meta)genomes. Interestingly, 60 - 95% of all phage ...

Early Viral Entry Assays for the Identification and Evaluation of Antiviral Compounds

Cell-based systems are useful for discovering antiviral agents. Dissecting the viral life cycle, particularly the early entry stages, allows a mechanistic approach to identify and evaluate antiviral agents that target specific steps of the viral entry. In this report, the methods of examining viral inactivation, viral attachment, and viral entry/fusion as antiviral assays for such purposes are described, using hepatitis C virus as a model. These assays should be useful for discovering novel antagonists/inhibitors to early viral entry and help expand the scope of candidate antiviral agents for further drug development.

Here, we present a protocol that examines specific steps of the viral entry to identify and evaluate novel antiviral agents.

Cell-based systems are useful for discovering antiviral agents. Dissecting the viral life cycle, particularly the early entry stages, allows a mechanistic ...

The Development of Lyophilized Loop-mediated Isothermal Amplification Reagents for the Detection of Coxiella burnetii

Coxiella burnetii, the agent causing Q fever, is an obligate intracellular bacterium. PCR based diagnostic assays have been developed for detecting C. burnetii DNA in cell cultures and clinical samples. PCR requires specialized equipment and extensive end user training, and therefore, it is not suitable for routine work especially in a resource-constrained area. We have developed a loop-mediated isothermal amplification (LAMP) assay to detect the presence of C. burnetii in patient samples. This method is performed at a single temperature around 60 &#176;C in a water bath or heating block. The sensitivity of this LAMP assay is very similar to PCR with a detection limit of about 25 copies per reaction. This report describes the preparation of the reaction using lyophilized reagents and visualization of results using hydroxynaphthol blue (HNB) or a UV lamp with fluorescent intercalating dye in the reaction. The LAMP reagents were lyophilized and stored at room temperature (RT) for one month without loss of detection sensitivity. This LAMP assay is particularly robust because the reaction mixture preparation does not involve complex steps. This method is ideal for use in resource-limited settings where Q fever is endemic.

The Development of Lyophilized Loop-mediated Isothermal Amplification Reagents for the Detection of Coxiella burnetii

We described here a simple loop-mediated isothermal amplification (LAMP) method using lyophilized reagents for the detection of C. burnetii in patient samples.

Coxiella burnetii, the agent causing Q fever, is an obligate intracellular bacterium. PCR based diagnostic assays have been developed for detecting C. ...