Name: a quantitative assay to study protein:dna interactions, discover transcriptional regulators of gene expression, and identify novel anti-tumor agents
Uploaded: 2013-08-31T07:00:00
Description: Watch this Scientific Journal Video about A Quantitative Assay to Study Protein:DNA Interactions, Discover Transcriptional Regulators of Gene Expression, and Identify Novel Anti-tumor Agents at JoVE.c

The technical assistance and instrumentation of the University of Maryland Greenebaum Cancer Center Translational Core Facility, especially Drs. Rena Lapidus and Mariola Sadowska, are gratefully acknowledged. The work responsible for the development of this assay was funded in part by NIH RO1CA108846, AHA Grant-in-Aid GRNT2130014, a VA Merit Award to A.P., and by the University of Maryland Cigarette Restitution Funds (CRF) provided to the Marlene &amp; Stewart Greenebaum Cancer Center.

Several steps are performed ahead of time and several reagents are prepared and stored prior to the procedure: (1) cell culture and protein isolation, (2) preparation of oligonucleotide, (3) preparation of 96-well plates, (4) nuclear extract incubation overnight. Procedure requires 2 days because of the overnight incubation of nuclear protein with DNA oligonucleotides.
1. Preparation of Buffers
1.1 Nuclear protein isolation
<ol>
	<li>Hypotonic Buffer: To prepare 100 ...

<ol>
	<li>Hellman, L. M., Fried, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrophoretic+mobility+shift+assay+(EMSA)+for+detecting+protein-nucleic+acid+interactions.">Electrophoretic mobility shift assay (EMSA) for detecting protein-nucleic acid interactions.</a> Nat. Protoc. 2, 1849-1861 (2007).</li><li>Bhattacharya, N., Sarno, A., Idler, I. S., 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=High-throughput+detection+of+nuclear+factor-kappaB+activity+using+a+sensitive+oligo-based+chemiluminescent+enzyme-linked+immunosorbent+assay.">High-throughput detection of nuclear factor-kappaB activity using a sensitive oligo-based chemiluminescent enzyme-linked immunosorbent assay.</a> Int. J. Cancer. 127, 404-411 (2010).</li><li>Hartzell, D. D., Trinklein, N. D., Mendez, J., 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=A+functional+analysis+of+the+CREB+signaling+pathway+using+HaloCHIP-chip+and+high+throughput+reporter+assays.">A functional analysis of the CREB signaling pathway using HaloCHIP-chip and high throughput reporter assays.</a> BMC Genomics. 10, 497 (2009).</li><li>Vuori, K. A., Ahlskog, J. K., Sistonen, L., Nikinmaa, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TransLISA,+a+novel+quantitative,+nonradioactive+assay+for+transcription+factor+DNA-binding+analyses.">TransLISA, a novel quantitative, nonradioactive assay for transcription factor DNA-binding analyses.</a> FEBS J. 276, 7366-7374 (2009).</li><li>D'Souza, D. R., Salib, M. M., Bennett, J., 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=Hyperglycemia+Regulates+RUNX2+Activation+and+Cellular+Wound+Healing+through+the+Aldose+Reductase+Polyol+Pathway.">Hyperglycemia Regulates RUNX2 Activation and Cellular Wound Healing through the Aldose Reductase Polyol Pathway.</a> J. Biol. Chem. 284, 17947-17955 (2009).</li><li>Underwood, K. F., D'Souza, D. R., Mochin, M. T., 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=Regulation+of+RUNX2+transcription+factor-DNA+interactions+and+cell+proliferation+by+Vitamin+D3+(cholecalciferol)+prohormone+activity.">Regulation of RUNX2 transcription factor-DNA interactions and cell proliferation by Vitamin D3 (cholecalciferol) prohormone activity.</a> J. Bone Miner Res. 27, 913-925 (2012).</li><li>Held, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetic+analysis+of+ß-galactosidase+activity+using+the+PowerWave+HT+and+Gen5+data+analysis+software:+basic+enzyme+kinetic+determinations.">Kinetic analysis of ß-galactosidase activity using the PowerWave HT and Gen5 data analysis software: basic enzyme kinetic determinations.</a> Biotek Instruments Application Note. , (2007).</li><li>Renard, P., Ernest, I., Houbion, 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=Development+of+a+sensitive+multi-well+colorimetric+assay+for+active+NFkappaB.">Development of a sensitive multi-well colorimetric assay for active NFkappaB.</a> Nucleic Acids Res. 29, E21 (2001).</li><li>Pommier, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DNA+topoisomerase+I+inhibitors:+chemistry,+biology,+and+interfacial+inhibition.">DNA topoisomerase I inhibitors: chemistry, biology, and interfacial inhibition.</a> Chem Rev. 109, 2894-2902 (2009).</li><li>Pennisi, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genomics.+ENCODE+project+writes+eulogy+for+junk+DNA.">Genomics. ENCODE project writes eulogy for junk DNA.</a> Science. 337, 1159-1161 (2012).</li></ol>

DNA-binding assays are used to measure the ability of transcription factors to interact with DNA. Assays for DNA binding include electrophoretic mobility shift (EMSA) 1 and chromatin immuneprecipitation (ChIP) based assays 3 as well as assays employing 96-well formats 4 such as chemiluminescent assays 2. The EMSA is non-quantitative and uses radiolabeled (32P) oligonucleotides. These are incubated with nuclear proteins and binding complexes are separated on agarose o...

DNA-binding assays have utility in measuring the ability of transcription factors to interact with DNA. Assays for DNA binding include electrophoretic mobility shift assays (EMSA) that depend on radiolabeled oligonucleotides 1 or chemiluminescence assays 2. Chromatin immuneprecipitation (ChIP) based assays 3 as well as assays employing 96-well formats 4 have also been described. However, the EMSA is a non-quantitative assay that requires the use of radiolabeled oligonucleotides. When nuclear proteins associate with the specific nucleotide promoter sequences, binding complexes are retarded on polyacrylamide gels and the specific transcription factor can be validated with an antibody "supershift". We have developed a quantitative DNA-binding assay using an enzyme-linked immunosorbent format (D-ELISA), which is able to measure the interaction of RUNX2 with DNA-binding sequences corresponding to defined promoter elements in RUNX2 target genes. Use of an anti-RUNX2 antibody provides specificity to the assay and the lack of radiolabel distinguish this assay from the traditional gel shift assay 5. Detection of binding complexes is possible with the use of a secondary antibody coupled to horseradish peroxidase (HRP), which converts an HRP substrate, tetramethyl benzidine (TMB) to a colored product for spectrophotometric analysis. The assay reported here can incorporate the use of mutated DNA oligonucleotides as controls and can be used for detection of competitive or non-competitive inhibitors of DNA binding. The screening of novel anti-tumor compounds is also possible with this assay.

<table border="1">
	<tbody>
		<tr>
			<td>Name of the Reagent</td>
			<td>Company</td>
			<td>Catalogue Number</td>
			<td>Comments (optional)</td>
		</tr>
		<tr>
			<td>Poly dI/dC</td>
			<td>GE Healthcare, Piscataway, NJ</td>
			<td>US20539-5UN</td>
			<td>1 U ~50mg</td>
		</tr>
		<tr>
			<td>RUNX2 antibody</td>
			<td>MBL International Corp., Woburn, MA</td>
			<td>D130-3</td>
			<td>1 mg/ml</td>
		</tr>
		<tr>
			<td>Fab-specific peroxidase conjugated antibody</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>A9917</td>
			<td>7.1 mg/ml</td>
		</tr>
		<tr>
			<td>TMB Substrate (tetramethyl benzidine)</td>
			<td>EXALPHA Biologicals, Shirley, MA</td>
			<td>X1189S</td>
			<td>100 ml</td>
		</tr>
		<tr>
			<td>Sodium carbonate</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>57995</td>
			<td>Plate-fixing</td>
		</tr>
		<tr>
			<td>Sulfuric Acid</td>
			<td>VWR, West Chester, PA</td>
			<td>BDH-39922-1</td>
			<td>Stop solution</td>
		</tr>
		<tr>
			<td>Multi-well plates</td>
			<td>Greiner Bio-One, Basel, Switzerland</td>
			<td>655996</td>
			<td>Avidin-coated, black sides</td>
		</tr>
		<tr>
			<td>HALT</td>
			<td>Thermo-Scientific/Pierce, Rockford, IL</td>
			<td>78440</td>
			<td>Protease and phosphatase inhibitors</td>
		</tr>
		<tr>
			<td>Chemicals</td>
			<td>Various manufacturers</td>
			<td>Laboratory grade</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>Table 1. Reagents</td>
		</tr>
		<tr>
			<td>Spectrophotometer: Biotrak II Visible plate reader</td>
			<td>Amersham Biosciences</td>
			<td>&nbsp;</td>
			<td>For use with stop reaction method</td>
		</tr>
		<tr>
			<td>Spectrophotometer: Bio-Tek Synergy HT Multi-reaction microplate reader</td>
			<td>Bio-Tek Instruments, Inc.</td>
			<td>&nbsp;</td>
			<td>For use with continuous kinetic monitoring</td>
		</tr>
		<tr>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>Table 2. Equipment</td>
		</tr>
	</tbody>
</table>

a quantitative assay to study protein:dna interactions, discover transcriptional regulators of gene expression, and identify novel anti-tumor agents

Many DNA-binding assays such as electrophoretic mobility shift assays (EMSA), chemiluminescent assays, chromatin immunoprecipitation (ChIP)-based assays, and multiwell-based assays are used to measure transcription factor activity. However, these assays are nonquantitative, lack specificity, may involve the use of radiolabeled oligonucleotides, and may not be adaptable for the screening of inhibitors of DNA binding. On the other hand, using a quantitative DNA-binding enzyme-linked immunosorbent assay (D-ELISA) assay, we demonstrate nuclear protein interactions with DNA using the RUNX2 transcription factor that depend on specific association with consensus DNA-binding sequences present on biotin-labeled oligonucleotides. Preparation of cells, extraction of nuclear protein, and design of double stranded oligonucleotides are described. Avidin-coated 96-well plates are fixed with alkaline buffer and incubated with nuclear proteins in nucleotide blocking buffer. Following extensive washing of the plates, specific primary antibody and secondary antibody incubations are followed by the addition of horseradish peroxidase substrate and development of the colorimetric reaction. Stop reaction mode or continuous kinetic monitoring were used to quantitatively measure protein interaction with DNA. We discuss appropriate specificity controls, including treatment with non-specific IgG or without protein or primary antibody. Applications of the assay are described including its utility in drug screening and representative positive and negative results are discussed.

The D-ELISA method is highly specific for the designated DNA-binding protein as long as a sequence-specific, double-stranded oligonucleotide containing three copies of the consensus RUNX2 binding site (ACACCA) is used. The primary antibody recognizing the protein factor also enhances the specificity. The secondary antibody contains covalently-linked horseradish peroxidase (HRP) that converts a clear substrate (tetramethyl benzidine) to a colored product for ease of detection (Figure 1). For these reasons...

Watch this Scientific Journal Video about A Quantitative Assay to Study Protein:DNA Interactions, Discover Transcriptional Regulators of Gene Expression, and Identify Novel Anti-tumor Agents at JoVE.c

A Quantitative Assay to Study Protein:DNA Interactions, Discover Transcriptional Regulators of Gene Expression, and Identify Novel Anti-tumor Agents

We developed a quantitative DNA-binding, ELISA-based assay to measure transcription factor interactions with DNA. High specificity for the RUNX2 protein was achieved with a consensus DNA-recognition oligonucleotide and specific monoclonal antibody. Colorimetric detection with an enzyme-coupled antibody substrate reaction was monitored in real time.

Many DNA-binding assays such as electrophoretic mobility shift assays (EMSA), chemiluminescent assays, chromatin immunoprecipitation (ChIP)-based assays, ...

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