Name: novel rna-binding proteins isolation by the rapid methodology
Uploaded: 2016-09-30T14:00:00
Description: Watch this Scientific Journal Video about Novel RNA-Binding Proteins Isolation by the RaPID Methodology at JoVE.com

We thank Prof. Jeff Gerst and Boris Slobodin for their helpful advice in setting up the RaPID protocol and providing the necessary plasmids. We also thank Dr. Avigail Atir-Lande for her help in establishing this protocol and Dr. Tamar Ziv from the Smoler Proteomics Center for her help with the LC-MS/MS analysis. We thank Prof. T.G. Kinzy (Rutgers) for the YEF3 antibody. This work was supported by grant 2011013 from the Binational Science Foundation.

Note: Insert a sequence consisting of 12 MS2-binding sites (MS2 loops; MS2L) into the desired genomic locus, usually between the open reading frame (ORF) and the 3&#39; UTR. A detailed protocol for this integration is provided elsewhere22. Verify proper insertion and expression by PCR, northern analysis or RT-PCR20,23. It is important to verify that the integration did not intervene with the synthesis of the 3&#39;UTR. In addition, a plasmid-expressing MS2-CP fused to SBP under the expression of an ...

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Various methods use the isolation of specific mRNAs to identify their associated proteins11,34 35. These methods apply in vitro and in vivo strategies to probe RNA-protein interactions. In vitro methods incubate exogenously transcribed RNA with cell lysate to capture RBPs and isolate RNP complexes36,37. An effective approach of this type was presented recently, which enabled the identification of novel proteins that bind a regulatory RNA motif18. A dr...

RNA-binding proteins (RBPs) represent about 10% of S. cerevisiae proteins1,2 and about 15% of mammalian proteins3-5. They are implicated in many cellular processes such as mRNA post-transcriptional processing and regulation, translation, ribosome biogenesis, tRNA aminoacylation and modification, chromatin remodeling, and more. An important subgroup of RBPs is the mRNA-binding proteins (mRNPs)6,7. In the course of mRNA maturation, different RBPs bind the transcript and mediate its nuclear processing, export out of the nucleus, cellular localization, translation and degradation6-8. Thus, the distinct set of RBPs bound to a particular transcript at any time point determines its processing and ultimately its fate.
The identification of RBPs associated with an mRNA could significantly improve our understanding of processes underlying their post-transcriptional regulation. Diverse genetic, microscopic, biochemical and bioinformatics methods have been used to identify proteins involved in mRNA regulation (reviewed in9-11). However, only a few of these methods enable the identification of proteins associated with a particular target mRNA. Of note is the Yeast Three Hybrid system (Y3H), which utilizes the mRNA of interest as bait to screen an expression library in yeast cells. Positive clones are usually observed through a growth selection or reporter expression12-14. The key advantage of this method is the large number of proteins that can be scanned in a cellular environment and the ability to measure the strength of the RNA-protein interaction. Drawbacks include the relatively large number of false positive results due to non-specific binding, and the high potential for false negative results due, in part, to misfolding of the fusion protein prey or the bait RNA.
An alternative to the genetic approach is affinity purification of RNA with its associated proteins. Poly A-containing mRNAs can be isolated through the use of oligo dT columns, and their associated proteins are detected by mass spectrometry. The RNA-protein interaction is conserved in its cellular context by crosslinking, which makes short-range covalent bonds. The use of the oligo dT column yields a global view of the entire proteome that is associated with any poly A-containing mRNA3,5,15. However, this does not provide a list of proteins that are associated with a particular mRNA. Very few methods are available to accomplish such an identification. The PAIR method entails the transfection of nucleic acid with complementarity to the target mRNA16,17. The nucleic acid is also attached to a peptide, which allows crosslinking to RBPs in close vicinity to the interaction site. After crosslinking, the RBP-peptide-nucleic acid can be isolated and subjected to proteomics analysis. Recently, an aptamer-based methodology was successfully applied to extracts from mammalian cell lines18. An RNA aptamer with improved affinity to streptavidin was developed and fused to a sequence of interest (AU-rich element (ARE) in this case). The aptamer-ARE RNA was attached to streptavidin beads and mixed with cell lysate. Proteins that associated with the ARE sequence were purified and identified by mass spectrometry (MS). Although this method detected associations that occur outside the cellular settings (i.e., in vitro), it is likely to be modified in the future so as to introduce the aptamers into the genome and thus enable the isolation of proteins associated with the mRNA while in the cellular milieu (i.e., in vivo). In yeast, where genetic manipulations are well established, the RaPID method (developed in Prof. Jeff Gerst&#39;s lab) provides a view of in vivo associations19. RaPID combines the specific and strong binding of the MS2 coat protein (MS2-CP) to the MS2 RNA sequence, and of the streptavidin-binding domain (SBP) to streptavidin conjugated beads. This enables efficient purification of MS2-tagged mRNAs through streptavidin beads. Moreover, expression of 12 copies of MS2 loops allows up to six MS2-CPs to bind simultaneously to the RNA and increase the efficiency of its isolation. This protocol was therefore suggested to enable the identification of novel mRNA-associated proteins once the eluted samples are subjected to proteomics analysis by mass spectrometry.
We recently utilized RaPID to identify novel proteins associated with the yeast PMP1 mRNA20. PMP1 mRNA was previously shown to be associated with the ER membrane and its 3&#39; untranslated region (UTR) was found to be a major determinant in this association21. Thus, RBPs that bind PMP1 3&#39; UTR are likely to play an important role in its localization. RaPID followed by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) resulted in the identification of many new proteins that interact with PMP120. Herein, we provide a detailed protocol of the RaPID methodology, important controls that need to be done, and technical tips that may improve yield and specificity.

<table border="0" cellpadding="0" cellspacing="0" width="632">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:239px;">Tris</td>
			<td style="width:107px;">sigma</td>
			<td style="width:119px;">T1503</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">SDS</td>
			<td>bio-lab</td>
			<td align="right">1981232300</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DTT</td>
			<td>sigma</td>
			<td>D9779</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Acidic Phenol (pH 4.3)</td>
			<td>sigma</td>
			<td>P4682</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Acidic Phenol: Chloroform (5:1, pH 4.3)</td>
			<td>sigma</td>
			<td>P1944</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Chloroform</td>
			<td>bio-lab</td>
			<td align="right">3080521</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Formaldehyde</td>
			<td>Frutarom</td>
			<td align="right">5551820</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glycine</td>
			<td>sigma</td>
			<td>G7126</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NP-40</td>
			<td>Calbiochem</td>
			<td align="right">492016</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Heparin</td>
			<td>Sigma</td>
			<td>H3393</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Phenylmethylsulfonyl Flouride (PMSF)</td>
			<td>Sigma</td>
			<td>P7626</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Leupeptin</td>
			<td>Sigma</td>
			<td>L2884</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Aprotinin</td>
			<td>Sigma</td>
			<td>A1153</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Soybean Trypsin Inhibitor</td>
			<td>Sigma</td>
			<td>T9003</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Pepstatin</td>
			<td>Sigma</td>
			<td>P5318</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DNase I</td>
			<td>Promega</td>
			<td>M610A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ribonuclease&#160; Inhibitor</td>
			<td>Takara</td>
			<td>2313A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glass Beads</td>
			<td>Sartorius</td>
			<td>BBI-8541701</td>
			<td>0.4-0.6mm diameter&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Mini BeadBeater</td>
			<td>BioSpec</td>
			<td colspan="2">Mini BeadBeater 16</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Guanidinium</td>
			<td>Sigma</td>
			<td>G4505</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Avidin</td>
			<td>Sigma</td>
			<td>A9275</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Streptavidin Beads</td>
			<td>GE Healthcare&#160;</td>
			<td>17-5113-01</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Bovine serum albumin (BSA)</td>
			<td>Sigma</td>
			<td>A7906</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Yeast tRNA</td>
			<td>Sigma</td>
			<td>R8508</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Biotin</td>
			<td>Sigma</td>
			<td>B4501</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Yeast extract</td>
			<td>Bacto</td>
			<td dir="LTR">288620</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">peptone</td>
			<td>Bacto</td>
			<td dir="LTR">211677</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glucose</td>
			<td>Sigma</td>
			<td>G8270</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1 x Phosphate-Buffered saline (PBS)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">0.2 M NaOH</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">4 x Laemmli Sample Buffer (LSB)</td>
			<td></td>
			<td></td>
			<td>0.2 M Tris-Hcl pH 6.8, 8% SDS, 0.4 M DTT, 40% glycerol, 0.04% Bromophenol-Blue.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hot phenol lysis buffer</td>
			<td></td>
			<td></td>
			<td>10 mM Tris pH 7.5, 10 mM EDTA, 0.5% SDS&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">3 M Sodium Acetate pH 5.2</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">100% and 70% Ethanol (EtOH)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">RNase-free water</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">RaPID lysis buffer</td>
			<td></td>
			<td></td>
			<td>20 mM Tris pH 7.5, 150 mM NaCl, 1.8 mM MgCl2, 0.5% NP-40, 5 mg/ml Heparin, 1 mM Dithiothreitol (DTT), 1 mM Phenylmethylsulfonyl Flouride (PMSF), 10 &#181;g/ml Leupeptin, 10 &#181;g/ml Aprotinin, 10 &#181;g/ml Soybean Trypsin Inhibitor, 10 &#181;g/ml Pepstatin, 20 U/ml DNase I, 100 U/ml Ribonuclease&#160; Inhibitor.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2x Cross-linking reversal buffer</td>
			<td></td>
			<td></td>
			<td dir="LTR">100 mM Tris pH 7.4, 10 mM EDTA, 20 mM DTT, 2 % SDS.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">RaPID wash buffer</td>
			<td></td>
			<td></td>
			<td>20 mM Tris-HCl pH 7.5,&#160; 300 mM NaCl, 0.5% NP-40</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">0.5 M EDTA pH 8</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Silver Stain Plus Kit</td>
			<td>Bio-Rad&#160;</td>
			<td>161-0449</td>
			<td>For detecting proteins in polyacrylamide gels</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">SD selective medium&#160;</td>
			<td></td>
			<td></td>
			<td>1.7 g/l Yeast nitrogen base with out amino acids and ammonium sulfate, 5 g/l Ammonium sulfate, 2% glucose, 350 mg/l Threonine, 40 mg/l Methionine, 40 mg/l Adenine, 50 mg/l Lysine, 50 mg/l Tryptophan, 20 mg/l Histidine, 80 mg/l Leucine, 30 mg/l Tyrosine, 40 mg/l Arginine</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Anti-eEF3 (EF3A,YEF3)</td>
			<td colspan="2">Gift from Kinzy TG. (UMDNJ Robert Wood Johnson Medical School)</td>
			<td>1:5,000</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Anti GFP antibody</td>
			<td>Santa Cruz</td>
			<td>sc-8334</td>
			<td>1:3,000</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Anti rabbit IgG-HRP conjugated</td>
			<td>SIGMA</td>
			<td>A9169</td>
			<td>1:10,000</td>
		</tr>
	</tbody>
</table>

novel rna-binding proteins isolation by the rapid methodology

RNA-binding proteins (RBPs) play important roles in every aspect of RNA metabolism and regulation. Their identification is a major challenge in modern biology. Only a few in vitro and in vivo methods enable the identification of RBPs associated with a particular target mRNA. However, their main limitations are the identification of RBPs in a non-cellular environment (in vitro) or the low efficiency isolation of RNA of interest (in vivo). An RNA-binding protein purification and identification (RaPID) methodology was designed to overcome these limitations in yeast and enable efficient isolation of proteins that are associated in vivo. To achieve this, the RNA of interest is tagged with MS2 loops, and co-expressed with a fusion protein of an MS2-binding protein and a streptavidin-binding protein (SBP). Cells are then subjected to crosslinking and lysed, and complexes are isolated through streptavidin beads. The proteins that co-purify with the tagged RNA can then be determined by mass spectrometry. We recently used this protocol to identify novel proteins associated with the ER-associated PMP1 mRNA. Here, we provide a detailed protocol of RaPID, and discuss some of its limitations and advantages.

RaPID enables the isolation of a specific target RNA with its associated proteins. Critical for its success is keeping the RNA intact as much as possible, thereby obtaining a sufficient amount of proteins. To determine the isolation efficiency and quality of RNA, northern analysis is performed (Figure 1A). Northern analysis has the advantage of directly reporting the efficiency and quality of RaPID. Thus, the relative amounts of full length and degradation products can be...

Watch this Scientific Journal Video about Novel RNA-Binding Proteins Isolation by the RaPID Methodology at JoVE.com

Novel RNA-Binding Proteins Isolation by the RaPID Methodology

RNA-protein interactions lie at the heart of many cellular processes. Here, we describe an in vivo method to isolate specific RNA and identify novel proteins that are associated with it. This could shed new light on how RNAs are regulated in the cell.

RNA-binding proteins (RBPs) play important roles in every aspect of RNA metabolism and regulation. Their identification is a major challenge in modern ...

The overall goal of this procedure is to efficiently isolate specific RNA with proteins that are associated with the RNA in vivo. This method can help answer key questions in RNA metabolism and regulation, such as what is a distinct set of fau-bee-pees bound to a particular transcript. The main advantage of this technique is the high efficiency of isolation, which allows follow up identification of noble mRNA associated proteins.The rapid methodology utilizes a yeast strain that co-expresses MS2-tagged MRNA and a fusion protein of an MS2 binding protein and a streptavadin binding protein. Grow 500 milliliters of yeast cells at 30 degrees Celsius in synthetic dextrose or SD selective medium to an OD600 of 0.8 to 1.0. When the cells are ready, centrifuge at 3000 times G for 4 minutes at room temperature and discard the supernatant.Wash the cells in PBS and centrifuge again. Discard the supernatant and re-suspend the cells in an equal volume of SD without methionine. Incubate for 45 to 60 minutes at 30 degrees celcius to induce expression of the fusion protein.After 45 to 60 minutes, set aside 10 milliliters of the cells for RNA extraction and use the remaining cells for rapid purification. To begin this procedure, add to the cells 1.35 milliliters of 37%formaldehyde, to a final concentration of 0.1%to cross-link the RNA-protein complexes. Continue incubating at 30 degrees Celsius for 10 minutes.To stop cross-linking, add 26.5 milliliters of 2.5 molar glycine, to a final concentration of 0.125 molar, and incubate at 30 degrees Celsius for 3 minutes. From here on, keep everything on ice and work quickly to minimize RNA degradation. Centrifuge the cells at 3000 times G for 4 minutes at 4 degrees Celsius.Discard the supernatant, add 45 milliliters of cold PBS, and centrifuge again. Remove the supernatant and re-suspend the cells in 5 milliliters of rapid lysis buffer that contains a high concentration of Rnase inhibitors. Divide the cell suspension into aliquots of 500 microliters in screw-capped microfuge tubes and add approximately 400 milligrams of chilled glass beads to each aliquot.Lyse the cells in a bead-beater for three minutes. Immediately put the lysate on ice. Transfer the lysate to new microfuge tubes.Cut the top off a 5 milliliter syringe and put it on an empty 15 milliliter tube to serve as an adapter for screw-cap tubes. Use a hot needle to pierce a small hole in the bottom of each tube and place them on top of the adapted 15 milliliter tubes. Centrifuge the tub assemblies at 3000 times G for one minute at 4 degrees Celsius to elute the lysate to the 15 milliliter tubes.Transfer the flowthrough from each 15 milliliter tube to a new 1.5 milliliter tube and centrifuge at 10, 000 times G for 10 minutes at 4 degrees Celsius to clear the cell debris. Pool the supernatant from all 1.5 milliliter tubes into a single 15 milliliter tube. Set aside 1/50th and 1/100th volume of the lysate for RNA and protein isolation respectively.Begin the rapid procedure for isolating RNA protein complexes by adding 300 micrograms of Avidin to the cell lysate. Incubate for 30 minutes at 4 degrees Celsius under constant rolling. While the cell lysate is being incubated with Avidin, pre-wash the streptavidin beads, transfer about 300 microliters of the streptavadin bead slurry to weigh 1.5 milliliters microcentriuge tube, centrifuge the preparation, and then remove the upper supernatant which will result in 250 microliters of beads.Add 1 milliliter of rapid lysis buffer to the beads and centrifuge at 660 times G for 2 minutes at 4 degrees Celsius. Remove the supernatant and wash again with rapid lysis buffer. To block the beads, add 0.5 milliliters of rapid lysis buffer, 0.5 milliliters of BSA, and 10 microliters of yeast TRNA and incubate for 1 hour at 4 degrees Celsius with constant rotation.Wash the beads twice with 1 milliliter of rapid lysis buffer. Add 250 microliters of the pre-washed streptavidin beads to the avidin containing lysate and incubate for 1 hour at 4 degrees Celsius with constant rotation. This incubation time is a compromise between providing sufficient binding time and minimizing the chances for RNA degradation.After one hour, centrifuge at 660 times G for 2 minutes at 4 degrees Celsius to clear the streptavidin beads. Transfer the supernatant to a 15 milliliter tube. Set aside 1/50th and 1/100th volume of the lysate for RNA and protein isolation respectively.Add 1 milliliter of rapid lysis buffer to the beads. Mix by pipetting, transfer to a new 1.5 milliliter microcentrifuge tube and centrifuge at 660 times G for 2 minutes at 4 degrees Celsius. Wash three more times with rapid lysis buffer.After the final wash with rapid lysis buffer, remove the supernatant, add 1 milliliter of rapid wash buffer, and rotate for 5 minutes at 4 degrees Celsius. Centrifuge and wash 2 more times with rapid wash buffer. Wash the beads with 1 milliliter of PBS and centrifuge as before.Remove the supernatant, add to the beads 120 microliters of PBS, and rotate for 5 minutes in a roller. Centrifuge as before and collect all the supernatant for RNA and protein extraction as the wash sample. To elute RNA and RNA-associated proteins, add 120 microliters of 6 millimolar biotin in PBS to the beads, and incubate for 45 minutes at 4 degrees Celsius with constant rotation.Centrifuge the beads and transfer the eluded material to a new 1.5 milliliter tube. Spin the eluted sample again and transfer the upper phase to a new 1.5 milliliter tube to ensure no carry-over of beads. Take samples for RNA or protein extraction.To determine the isolation efficiency and quality of RNA, Northern Analysis was performed for two tagged RNAs. PMP1 and FPR1, from cast cell lysis, rapid cell lysis, and after elution with biotin. Ribosomal RNAs were detected by ethidium bromide staining, and the lack of ribosomal RNAs in the elution sample indicates the stringency of purification.The stringency and specificity of the purification are further demonstrated by the lack of a signal of an untagged MRNA in the elution samples. The apparent signal in the FPR1 lane, which is not of the size of ACT1, is a leftover from previous hybridization with the MS2L probe. Although the input RNA is somewhat more degraded compared to the RNA that was purified by the Hot Phenol protocol, a significant amount of full length tagged RNA is isolated specifically, as revealed by the strong signal in the elution fractions.Protein samples can be analyzed by SDS-PAGE and silverstaining prior to proteomics analysis. The MS2-CP-GFP-SBP fusion protein, indicated by the arrow, demonstrates equal protein loading. The asterisks indicate bands with differential intensities that were later cut out of the gel for mass-spectrometry analysis.While attempting this procedure, it's important to wear gloves, ensure a clean work-area, prepare solution with RNA free water, and work quickly and efficiently to reduce protocol time. Don't forget that working with reagents like phenol and formaldehyde can be extremely hazardous, and precautions such as working in a chemical hood should always be taken while performing this procedure. After watching this video, you should have a good understanding of how to efficiently and effectively purify RNA of fayn-tress and its associated body.Following this procedure, other methods like RNA-Seq can be performed in order to detect RNAs that bind the transcript of interest.

novel-rna-binding-proteins-isolation-by-the-rapid-methodology

Research

JoVE Journal

Genetics

Conjugative Mating Assays for Sequence-specific Analysis of Transfer Proteins Involved in Bacterial Conjugation

The transfer of genetic material by bacterial conjugation is a process that takes place via complexes formed by specific transfer proteins. In Escherichia coli, these transfer proteins make up a DNA transfer machinery known as the mating pair formation, or DNA transfer complex, which facilitates conjugative plasmid transfer. The objective of this paper is to provide a method that can be used to determine the role of a specific transfer protein that is involved in conjugation using a series of deletions and/or point mutations in combination with mating assays. The target gene is knocked out on the conjugative plasmid and is then provided in trans through the use of a small recovery plasmid harboring the target gene. Mutations affecting the target gene on the recovery plasmid can reveal information about functional aspects of the target protein that result in the alteration of mating efficiency of donor cells harboring the mutated gene. Alterations in mating efficiency provide insight into the role and importance of the particular transfer protein, or a region therein, in facilitating conjugative DNA transfer. Coupling this mating assay with detailed three-dimensional structural studies will provide a comprehensive understanding of the function of the conjugative transfer protein as well as provide a means for identifying and characterizing regions of protein-protein interaction.

Here, we present a protocol to knockout a gene of interest involved in plasmid conjugation and subsequently analyze the impact of its absence using mating assays. The function of the gene is further explored to a specific region of its sequence using deletion or point mutations.

The transfer of genetic material by bacterial conjugation is a process that takes place via complexes formed by specific transfer proteins. In Escherichia ...

Kinetics of Lagging-strand DNA Synthesis In Vitro by the Bacteriophage T7 Replication Proteins

Here we provide protocols for the kinetic examination of lagging-strand DNA synthesis in vitro by the replication proteins of bacteriophage T7. The T7 replisome is one of the simplest replication systems known, composed of only four proteins, which is an attractive feature for biochemical experiments. Special emphasis is placed on the synthesis of ribonucleotide primers by the T7 primase-helicase, which are used by DNA polymerase to initiate DNA synthesis. Because the mechanisms of DNA replication are conserved across evolution, these protocols should be applicable, or useful as a conceptual springboard, to investigators using other model systems. The protocols described here are highly sensitive and an experienced investigator can perform these experiments and obtain data for analysis in about a day. The only specialized piece of equipment required is a rapid-quench flow instrument, but this piece of equipment is relatively common and available from various commercial sources. The major drawbacks of these assays, however, include the use of radioactivity and the relative low throughput.

Kinetics of Lagging-strand DNA Synthesis In Vitro by the Bacteriophage T7 Replication Proteins

We describe sensitive, gel-based discontinuous assays to examine the kinetics of lagging-strand initiation using the replication proteins of bacteriophage T7.

Here we provide protocols for the kinetic examination of lagging-strand DNA synthesis in vitro by the replication proteins of bacteriophage T7. The T7 ...

Bidirectional Retroviral Integration Site PCR Methodology and Quantitative Data Analysis Workflow

Integration Site (IS) assays are a critical component of the study of retroviral integration sites and their biological significance. In recent retroviral gene therapy studies, IS assays, in combination with next-generation sequencing, have been used as a cell-tracking tool to characterize clonal stem cell populations sharing the same IS. For the accurate comparison of repopulating stem cell clones within and across different samples, the detection sensitivity, data reproducibility, and high-throughput capacity of the assay are among the most important assay qualities. This work provides a detailed protocol and data analysis workflow for bidirectional IS analysis. The bidirectional assay can simultaneously sequence both upstream and downstream vector-host junctions. Compared to conventional unidirectional IS sequencing approaches, the bidirectional approach significantly improves IS detection rates and the characterization of integration events at both ends of the target DNA. The data analysis pipeline described here accurately identifies and enumerates identical IS sequences through multiple steps of comparison that map IS sequences onto the reference genome and determine sequencing errors. Using an optimized assay procedure, we have recently published the detailed repopulation patterns of thousands of Hematopoietic Stem Cell (HSC) clones following transplant in rhesus macaques, demonstrating for the first time the precise time point of HSC repopulation and the functional heterogeneity of HSCs in the primate system. The following protocol describes the step-by-step experimental procedure and data analysis workflow that accurately identifies and quantifies identical IS sequences.

This manuscript describes the experimental procedure and software analysis for a bidirectional integration site assay that can simultaneously analyze upstream and downstream vector-host junction DNA. Bidirectional PCR products can be used for any downstream sequencing platform. The resulting data are useful for a high-throughput, quantitative comparison of integrated DNA targets.

Integration Site (IS) assays are a critical component of the study of retroviral integration sites and their biological significance. In recent retroviral ...

A Standard Methodology to Examine On-site Mutagenicity As a Function of Point Mutation Repair Catalyzed by CRISPR/Cas9 and SsODN in Human Cells

Combinatorial gene editing using CRISPR/Cas9 and single-stranded oligonucleotides is an effective strategy for the correction of single-base point mutations, which often are responsible for a variety of human inherited disorders. Using a well-established cell-based model system, the point mutation of a single-copy mutant eGFP gene integrated into HCT116 cells has been repaired using this combinatorial approach. The analysis of corrected and uncorrected cells reveals both the precision of gene editing and the development of genetic lesions, when indels are created in uncorrected cells in the DNA sequence surrounding the target site. Here, the specific methodology used to analyze this combinatorial approach to the gene editing of a point mutation, coupled with a detailed experimental strategy to measuring indel formation at the target site, is outlined. This protocol outlines a foundational approach and workflow for investigations aimed at developing CRISPR/Cas9-based gene editing for human therapy. The conclusion of this work is that on-site mutagenesis takes place as a result of CRISPR/Cas9 activity during the process of point mutation repair. This work puts in place a standardized methodology to identify the degree of mutagenesis, which should be an important and critical aspect of any approach destined for clinical implementation.

This protocol outlines the workflow of a CRISPR/Cas9-based gene editing system for the repair of point mutations in mammalian cells. Here, we use a combinatorial approach to gene editing with a detailed follow-on experimental strategy for measuring indel formation at the target site&#8212;in essence, analyzing onsite mutagenesis.

Combinatorial gene editing using CRISPR/Cas9 and single-stranded oligonucleotides is an effective strategy for the correction of single-base point ...

Methodology for Accurate Detection of Mitochondrial DNA Methylation

Quantification of DNA methylation can be achieved using bisulfite sequencing, which takes advantage of the property of sodium bisulfite to convert unmethylated cytosine into uracil, in a single-stranded DNA context. Bisulfite sequencing can be targeted (using PCR) or performed on the whole genome and provides absolute quantification of cytosine methylation at the single base-resolution. Given the distinct nature of nuclear- and mitochondrial DNA, notably in the secondary structure, adaptions of bisulfite sequencing methods for investigating cytosine methylation in mtDNA should be made. Secondary and tertiary structure of mtDNA can indeed lead to bisulfite sequencing artifacts leading to false-positives due to incomplete denaturation poor access of bisulfite to single-stranded DNA. Here, we describe a protocol using an enzymatic digestion of DNA with BamHI coupled with bioinformatic analysis pipeline to allow accurate quantification of cytosine methylation levels in mtDNA. In addition, we provide guidelines for designing the bisulfite sequencing primers specific to mtDNA, in order to avoid targeting undesirable NUclear MiTochondrial segments (NUMTs) inserted into the nuclear genome.

Here, we present a protocol to allow accurate quantification of mitochondrial DNA (mtDNA) methylation. In this protocol, we describe an enzymatic digestion of DNA with BamHI coupled with a bioinformatic analysis pipeline which can be used to avoid overestimation of mtDNA methylation levels caused by the secondary structure of mtDNA.

Quantification of DNA methylation can be achieved using bisulfite sequencing, which takes advantage of the property of sodium bisulfite to convert ...

Novel Sequence Discovery by Subtractive Genomics

Subtractive genomics can be used in any research where the goal is to identify the sequence of a gene, protein, or general region that is embedded in a larger genomic context. Subtractive genomics enables a researcher to isolate a target sequence of interest (T) by comprehensive sequencing and subtracting out known genetic elements (reference, R). The method can be used to identify novel sequences such as mitochondria, chloroplasts, viruses, or germline restricted chromosomes, and is particularly useful when T cannot be easily isolated from R. Beginning with the comprehensive genomic data (R + T), the method uses Basic Local Alignment Search Tool (BLAST) against a reference sequence, or sequences, to remove the matching known sequences (R), leaving behind the target (T). For subtraction to work best, R should be a relatively complete draft that is missing T. Since sequences remaining after subtraction are tested through quantitative Polymerase Chain Reaction (qPCR), R does not need to be complete for the method to work. Here we link computational steps with experimental steps into a cycle that can be iterated as needed, sequentially removing multiple reference sequences and refining the search for T. The advantage of subtractive genomics is that a completely novel target sequence can be identified even in cases in which physical purification is difficult, impossible, or expensive. A drawback of the method is finding a suitable reference for subtraction and obtaining T-positive and negative samples for qPCR testing. We describe our implementation of the method in the identification of the first gene from the germline-restricted chromosome of zebra finch. In that case computational filtering involved three references (R), sequentially removed over three cycles: an incomplete genomic assembly, raw genomic data, and transcriptomic data.

The purpose of this protocol is to use a combination of computational and bench research to find novel sequences that cannot be easily separated from a co-purifying sequence, which may be only partially known.

Subtractive genomics can be used in any research where the goal is to identify the sequence of a gene, protein, or general region that is embedded in a ...

Sequencing of mRNA from Whole Blood using Nanopore Sequencing

Sequencing in remote locations and resource-poor settings presents unique challenges. Nanopore sequencing can be successfully used under such conditions, and was deployed to West Africa during the recent Ebola virus epidemic, highlighting this possibility. In addition to its practical advantages (low cost, ease of equipment transport and use), this technology also provides fundamental advantages over second-generation sequencing approaches, particularly the very long read length, ability to directly sequence RNA, and real-time availability of data. Raw read accuracy is lower than with other sequencing platforms, which represents the main limitation of this technology; however, this can be partially mitigated by the high read depth generated. Here, we present a field-compatible protocol for sequencing of the mRNAs encoding for Niemann-Pick C1, which is the cellular receptor for ebolaviruses. This protocol encompasses extraction of RNA from animal blood samples, followed by RT-PCR for target enrichment, barcoding, library preparation, and the sequencing run itself, and can be easily adapted for use with other DNA or RNA targets.

Nanopore sequencing is a novel technology that allows cost-effective sequencing in remote locations and resource-poor settings. Here, we present a protocol for sequencing of mRNAs from whole blood that is compatible with such conditions.

Sequencing in remote locations and resource-poor settings presents unique challenges. Nanopore sequencing can be successfully used under such conditions, ...

Mass Spectrometry-Based Proteomics Analyses Using the OpenProt Database to Unveil Novel Proteins Translated from Non-Canonical Open Reading Frames

Genome annotation is central to today's proteomic research as it draws the outlines of the proteomic landscape. Traditional models of open reading frame (ORF) annotation impose two arbitrary criteria: a minimum length of 100 codons and a single ORF per transcript. However, a growing number of studies report expression of proteins from allegedly non-coding regions, challenging the accuracy of current genome annotations. These novel proteins were found encoded either within non-coding RNAs, 5' or 3' untranslated regions (UTRs) of mRNAs, or overlapping a known coding sequence (CDS) in an alternative ORF. OpenProt is the first database that enforces a polycistronic model for eukaryotic genomes, allowing annotation of multiple ORFs per transcript. OpenProt is freely accessible and offers custom downloads of protein sequences across 10 species. Using OpenProt database for proteomic experiments enables novel proteins discovery and highlights the polycistronic nature of eukaryotic genes. The size of OpenProt database (all predicted proteins) is substantial and need be taken in account for the analysis. However, with appropriate false discovery rate (FDR) settings or the use of a restricted OpenProt database, users will gain a more realistic view of the proteomic landscape. Overall, OpenProt is a freely available tool that will foster proteomic discoveries.

OpenProt is a freely accessible database that enforces a polycistronic model of eukaryotic genomes. Here, we present a protocol for the use of OpenProt databases when interrogating mass spectrometry datasets. Using OpenProt database for analysis of proteomic experiments allows for discovery of novel and previously undetectable proteins.

Genome annotation is central to today's proteomic research as it draws the outlines of the proteomic landscape. Traditional models of open reading frame ...

An Assay for Quantifying Protein-RNA Binding in Bacteria

In the initiation step of protein translation, the ribosome binds to the initiation region of the mRNA. Translation initiation can be blocked by binding of an RNA binding protein (RBP) to the initiation region of the mRNA, which interferes with ribosome binding. In the presented method, we utilize this blocking phenomenon to quantify the binding affinity of RBPs to their cognate and non-cognate binding sites. To do this, we insert a test binding site in the initiation region of a reporter mRNA and induce the expression of the test RBP. In the case of RBP-RNA binding, we observed a sigmoidal repression of the reporter expression as a function of RBP concentration. In the case of no-affinity or very low affinity between binding site and RBP, no significant repression was observed. The method is carried out in live bacterial cells, and does not require expensive or sophisticated machinery. It is useful for quantifying and comparing between the binding affinities of different RBPs that are functional in bacteria to a set of designed binding sites. This method may be inappropriate for binding sites with high structural complexity. This is due to the possibility of repression of ribosomal initiation by complex mRNA structure in the absence of RBP, which would result in lower basal reporter gene expression, and thus less-observable reporter repression upon RBP binding.

In this method, we quantify the binding affinity of RNA binding proteins (RBPs) to cognate and non-cognate binding sites using a simple, live, reporter assay in bacterial cells. The assay is based on repression of a reporter gene.

In the initiation step of protein translation, the ribosome binds to the initiation region of the mRNA. Translation initiation can be blocked by binding ...

Exploring Sequence Space to Identify Binding Sites for Regulatory RNA-Binding Proteins

Gene regulation plays an important role in all cells. Transcriptional, post-transcriptional (or RNA processing), translational, and post-translational steps are used to regulate specific genes. Sequence-specific nucleic acid-binding proteins target specific sequences to control spatial or temporal gene expression. The binding sites in nucleic acids are typically characterized by mutational analysis. However, numerous proteins of interest have no known binding site for such characterization. Here we describe an approach to identify previously unknown binding sites for RNA-binding proteins. It involves iterative selection and amplification of sequences starting with a randomized sequence pool. Following several rounds of these steps-transcription, binding, and amplification-the enriched sequences are sequenced to identify a preferred binding site(s). Success of this approach is monitored using in vitro binding assays. Subsequently, in vitro and in vivo functional assays can be used to assess the biological relevance of the selected sequences. This approach allows identification and characterization of a previously unknown binding site(s) for any RNA-binding protein for which an assay to separate protein-bound and unbound RNAs exists.

Sequence specificity is critical for gene regulation. Regulatory proteins that recognize specific sequences are important for gene regulation. Defining functional binding sites for such proteins is a challenging biological problem. An iterative approach for identification of a binding site for an RNA-binding protein is described here and is applicable to all RNA-binding proteins.

Gene regulation plays an important role in all cells. Transcriptional, post-transcriptional (or RNA processing), translational, and post-translational ...