Name: identification of transcription factor regulators using medium-throughput screening of arrayed libraries and a dual-luciferase-based reporter
Uploaded: 2020-03-27T13:00:00
Description: Watch this Scientific Journal Video about Identification of Transcription Factor Regulators using Medium-Throughput Screening of Arrayed Libraries and a Dual-Luciferase-Based Reporter at JoVE.com

We would like to thank Emily Norton and Mikaelan Cucciarre-Stuligross for assisting in the preparation of shRNA vectors. This work was supported in part by a Susan G. Komen Career Catalyst Grant that awarded to J.M.L. (#CCR17477184).

NOTE: A schematic summary of this protocol is shown in Figure 1.
1. Lentiviral vector library preparation
NOTE: The demonstrated screen used an arrayed shRNA library purchased as glycerol stocks in 96-well plates, but libraries can also be assembled manually based on a list of candidates. Appropriate controls should be considered and included in any library. This includes a non-targeting control shRNA (shNTC), a control shRNA targeting th...

In this study, we demonstrate an approach for medium-throughput screening of arrayed viral libraries in combination with a dual-luciferase-based transcriptional reporter assay that can be used to identify and test novel regulators of transcription factors. It is critical to characterize and optimize the reporter system for each cell line prior to any screen. Experiments should be done to confirm that the reporter is responsive to altered activity of the transcription factor being investigated and the magnitude of change ...

The purpose of this assay is to use viral libraries to identify regulators of transcription factors in a relatively quick and inexpensive manner. Aberrant transcriptional activity is associated with cancer and metastasis1,2,3,4,5,6, so targeting transcription factors in cancer cells is a promising therapeutic approach. However, transcription factors are often difficult to target pharmacologically7 and many are required for normal cellular function in adult tissues8,9,10. Targeting the cancer-associated pathways that aberrantly activate transcription factors to drive disease is a more feasible approach with the potential to have less severe side effects. The commercial availability of arrayed lentiviral and retroviral RNAi, CRISPR/CAS9, cDNA, or ORF libraries allows researchers to test the importance of numerous genes in a single experiment. However, a reliable readout for altered transcriptional activity is required.
Here, we describe the use of a dual-luciferase-based transcriptional reporter assay and arrayed lentiviral libraries to identify proteins that regulate transcription factors in cancer cells. In this assay, shRNAs that target cancer-associated genes are delivered to mammalian cancer cells via lentiviral transduction and cells are selected for stable integration using puromycin. The cells are next transfected with a reporter construct that expresses firefly luciferase driven by a promoter specific to the transcription factor that is being investigated and a control construct that expresses Renilla luciferase from a constitutively active promoter that is not responsive to the transcription factor being investigated. We demonstrate this approach with a proof-of-concept screen for regulators of YAP and TAZ, the critical downstream effectors of the Hippo pathway8,10,11. Abnormal activity of YAP and TAZ promotes several steps of the metastatic cascade11 and is observed in many cancers11,12,13. However, how YAP and TAZ become aberrantly activated in some cancer cells is not yet fully understood. YAP and TAZ do not bind DNA, but instead are recruited to promoters by other transcription factors. Members of the TEA domain (TEAD) family of transcription factors are the major binding partners for YAP and TAZ, and are critical for most YAP and TAZ-dependent functions. Our reporter construct expresses firefly luciferase from a YAP/TAZ-TEAD-responsive promoter and previous studies have demonstrated that it faithfully detects changes in YAP-TEAD and TAZ-TEAD transcriptional activity2,14,15.
Our approach is rapid, medium-throughput, and does not require screening facilities, automated robots, or deep sequencing of pooled libraries. The costs are relatively low and there are numerous commercially available libraries to choose from. The required equipment and reagents are also relatively standard in most laboratories. It can be used to screen for regulators of virtually any transcription factor if a luciferase-based reporter exists or is generated. We use this approach to screen shRNAs in cancer cells, but any cell line that can be transfected with reasonable efficiency could be used with any type of arrayed library.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>2.0 ml 96-well deep well polypropylene plate</td>
			<td>USA Scientific</td>
			<td>1896-2000</td>
			<td>For bacterial mini-prep</td>
		</tr>
		<tr>
			<td>Trypsin - 2.50%</td>
			<td>Gibco</td>
			<td>15090-046</td>
			<td>Component of trypsin-EDTA</td>
		</tr>
		<tr>
			<td>96 well flat bottom white assay plate</td>
			<td>Corning</td>
			<td>3922</td>
			<td>For dual-luciferase assay</td>
		</tr>
		<tr>
			<td>Ampicillin - 100 mg/ml</td>
			<td>Sigma-Aldrich</td>
			<td>45-10835242001-EA</td>
			<td>For bacterial mini-prep</td>
		</tr>
		<tr>
			<td>Bacto-tryptone - powder</td>
			<td>Sigma-Aldrich</td>
			<td>95039</td>
			<td>Component of LB broth</td>
		</tr>
		<tr>
			<td>Dual-luciferase reporter assay system, which include LAR II reagent (reagent A), Stop &#38; Glo substrate (reagent B substrate) and Stop &#38; Glo buffer (reagent B buffer) - Kit</td>
			<td>Promega</td>
			<td>E1960</td>
			<td>For dual-luciferase assay</td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s phosphate buffered saline w/o calcium, magnesium and phenol red - 9.6 g/L</td>
			<td>Himedia</td>
			<td>TS1006</td>
			<td>For PBS</td>
		</tr>
		<tr>
			<td>EDTA - 0.5 M</td>
			<td>VWR</td>
			<td>97061-406</td>
			<td>Component of trypsin-EDTA</td>
		</tr>
		<tr>
			<td>Ethanol - 100%</td>
			<td>Pharmco-AAPER</td>
			<td>111000200</td>
			<td>For bacterial mini-prep</td>
		</tr>
		<tr>
			<td>Foetal Bovine Serum - 100%</td>
			<td>VWR</td>
			<td>97068-085</td>
			<td>Component of complete growth media</td>
		</tr>
		<tr>
			<td>Hexadimethrine bromide (Polybrene) - 8 mg/ml</td>
			<td>Sigma-Aldrich</td>
			<td>45-H9268</td>
			<td>For virus infection</td>
		</tr>
		<tr>
			<td>HyClone DMEM/High glucose - 4 mM L-Glutamine; 4500 mg/L glucose; sodium pyruvate</td>
			<td>GE Healthcare life sciences</td>
			<td>SH30243.01</td>
			<td>Component of complete growth media</td>
		</tr>
		<tr>
			<td>I3-P/i3 Multi-Mode Microplate/EA</td>
			<td>Molecular devices</td>
			<td></td>
			<td>For dual-luciferase assay</td>
		</tr>
		<tr>
			<td>L-Glutamine - 200 mM</td>
			<td>Gibco</td>
			<td>25030-081</td>
			<td>Component of complete growth media</td>
		</tr>
		<tr>
			<td>Lipofectamine 3000 (Transfection Reagent 2) - 100%</td>
			<td>Life technologies</td>
			<td>L3000008</td>
			<td>For transfections</td>
		</tr>
		<tr>
			<td>Molecular Biology Water - 100%</td>
			<td>VWR</td>
			<td>02-0201-0500</td>
			<td>For dilution of shRNA vector for virus packaging</td>
		</tr>
		<tr>
			<td>NaCl - powder</td>
			<td>BDH</td>
			<td>BDH9286</td>
			<td>Component of LB broth</td>
		</tr>
		<tr>
			<td>NanoDrop One Microvolume UV-Vis Spectrophotometer</td>
			<td>Thermo scientific</td>
			<td></td>
			<td>For measuring vector DNA concentration</td>
		</tr>
		<tr>
			<td>Opti-MEM (Transfection Buffer) - 100%</td>
			<td>Gibco</td>
			<td>31985-062</td>
			<td>For transfections</td>
		</tr>
		<tr>
			<td>Penicillin Streptomycin - 10,000 Unit/ml (Penicillin); 10,000 &#181;g/ml (Streptomycin)</td>
			<td>Gibco</td>
			<td>15140-122</td>
			<td>Component of complete growth media</td>
		</tr>
		<tr>
			<td>PureLink Quick Plasmid Miniprep Kit - Kit</td>
			<td>Thermo Fisher Scientific</td>
			<td>K210010</td>
			<td>For bacterial mini-prep</td>
		</tr>
		<tr>
			<td>Puromycin - 2.5 mg/ml</td>
			<td>Sigma-Aldrich</td>
			<td>45-P7255</td>
			<td>For antibiotic selection after infection</td>
		</tr>
		<tr>
			<td>TC20 automated cell counter</td>
			<td>Bio-Rad</td>
			<td></td>
			<td>For cell counting</td>
		</tr>
		<tr>
			<td>X-tremeGENE 9 DNA transfection reagent (Transfection Reagent 1) - 100%</td>
			<td>Roche</td>
			<td>6365787001</td>
			<td>For virus packaging</td>
		</tr>
		<tr>
			<td>Yeast extract - powder</td>
			<td>VWR</td>
			<td>J850</td>
			<td>Component of LB broth</td>
		</tr>
		<tr>
			<td>P3000 (Transfection Reagent 3) - 100%</td>
			<td>Life technologies</td>
			<td>L3000008</td>
			<td>For transfections</td>
		</tr>
	</tbody>
</table>

identification of transcription factor regulators using medium-throughput screening of arrayed libraries and a dual-luciferase-based reporter

Transcription factors can alter the expression of numerous target genes that influence a variety of downstream processes making them good targets for anti-cancer therapies. However, directly targeting transcription factors is often difficult and can cause adverse side effects if the transcription factor is necessary in one or more adult tissues. Identifying upstream regulators that aberrantly activate transcription factors in cancer cells offers a more feasible alternative, particularly if these proteins are easy to drug. Here, we describe a protocol that can be used to combine arrayed medium-scale lentiviral libraries and a dual-luciferase-based transcriptional reporter assay to identify novel regulators of transcription factors in cancer cells. Our approach offers a quick, easy, and inexpensive way to test hundreds of genes in a single experiment. To demonstrate the use of this approach, we performed a screen of an arrayed lentiviral RNAi library containing several regulators of Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), two transcriptional co-activators that are the downstream effectors of the Hippo pathway. However, this approach could be modified to screen for regulators of virtually any transcription factor or co-factor and could also be used to screen CRISPR/CAS9, cDNA, or ORF libraries.

Our YAP/TAZ-TEAD reporter construct (pGL3-5xMCAT (SV)-492,14,15) contains a minimal SV-49 promoter with 5 repeats of the canonical TEAD binding element (MCAT)15 driving the firefly luciferase gene (Figure 1). It is co-transfected into cells along with the PRL-TK control vector (Promega), which expresses Renilla luciferase from the con...

Watch this Scientific Journal Video about Identification of Transcription Factor Regulators using Medium-Throughput Screening of Arrayed Libraries and a Dual-Luciferase-Based Reporter at JoVE.com

Identification of Transcription Factor Regulators using Medium-Throughput Screening of Arrayed Libraries and a Dual-Luciferase-Based Reporter

To identify novel regulators of transcription factors, we developed an approach to screen arrayed lentiviral or retroviral RNAi libraries using a dual-luciferase-based transcriptional reporter assay. This approach offers a quick and relatively inexpensive way to screen hundreds of candidates in a single experiment.

Transcription factors can alter the expression of numerous target genes that influence a variety of downstream processes making them good targets for ...

Research

JoVE Journal

Cancer Research

Sectioning Mammary Gland Whole Mounts for Lesion Identification

Normal mammary gland development may be altered by exposure to environmental toxicants and pharmaceutical products, excessive exposure to hormones, and ...

Flow Cytometry-based Drug Screening System for the Identification of Small Molecules That Promote Cellular Differentiation of Glioblastoma Stem Cells

Glioblastoma (GBM) is the most common and most lethal primary brain tumor in adults, causing roughly 14,000 deaths each year in the U.S. alone. Median ...

Live Cell Imaging of the TGF-	&beta;/Smad3 Signaling Pathway In Vitro and In Vivo Using an Adenovirus Reporter System

Live Cell Imaging of the TGF-	ÃƒÆ’Ã…Â½Ãƒâ€šÃ‚Â²/Smad3 Signaling Pathway In Vitro and In Vivo Using an Adenovirus Reporter System

Transforming Growth Factor &#946; (TGF-&#946;) signaling regulates many important functions required for cellular homeostasis and is commonly found ...

Analysis of Cancer Cell Invasion and Anti-metastatic Drug Screening Using Hydrogel Micro-chamber Array (HMCA)-based Plates

Analysis of Cancer Cell Invasion and Anti-metastatic Drug Screening Using Hydrogel Micro-chamber Array HMCA-based Plates

Cancer metastasis is known to cause 90% of cancer lethality. Metastasis is a multistage process which initiates with the penetration/invasion of tumor ...

Isolation of Exosome-Enriched Extracellular Vesicles Carrying Granulocyte-Macrophage Colony-Stimulating Factor from Embryonic Stem Cells

Embryonic stem cells (ESCs) are pluripotent stem cells capable of self-renewal and differentiation into all types of embryonic cells. Like many other cell ...

Establishment and Characterization of Small Bowel Neuroendocrine Tumor Spheroids

Small bowel neuroendocrine tumors (SBNETs) are rare cancers originating from enterochromaffin cells of the gut. Research in this field has been limited ...

Mapping the Structure-Function Relationships of Disordered Oncogenic Transcription Factors Using Transcriptomic Analysis

Many cancers are characterized by chromosomal translocations which result in the expression of oncogenic fusion transcription factors. Typically, these ...

Identification of EGFR and RAS Inhibitors using Caenorhabditis elegans

Identification of EGFR and RAS Inhibitors using Caenorhabditis elegans

The changes in the plasma membrane localization of the epidermal growth factor receptor (EGFR) and its downstream effector RAS have been implicated in ...

Discovery of Metastatic Regulators using a Rapid and Quantitative Intravital Chick Chorioallantoic Membrane Model

Recent advances in cancer research has illustrated the highly complex nature of cancer metastasis. Multiple genes or genes networks have been found to be ...

A Rapid Screening Workflow to Identify Potential Combination Therapy for GBM using Patient-Derived Glioma Stem Cells

The glioma stem cells (GSCs) are a small fraction of cancer cells which play essential roles in tumor initiation, angiogenesis, and drug resistance in ...