This work was supported by Merit Review Awards to Douglas D. Ross and to Arif Hussain from the Department of Veterans&#39; Affairs.

1. In Silico Prediction of Alternative First Exons of Bcrp1 Using BLAST Analysis of Mouse EST Database
Note: This protocol describes how to search the mouse expressed sequence tag (EST) database for ESTs with sequence similarity to exon 2 of Bcrp1 (which contains the translational start site) and then how to align the matching EST sequences to genomic sequences to ascertain their location in the mouse Bcrp1 gene relative to the 5&#39; end of Bcrp1 exon 2.
<ol>
	<li>Obtain the sequen...

<ol>
	<li>Kimura, K., 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=Diversification+of+transcriptional+modulation:+large-scale+identification+and+characterization+of+putative+alternative+promoters+of+human+genes.">Diversification of transcriptional modulation: large-scale identification and characterization of putative alternative promoters of human genes.</a> Genome Res. 16 (1), 55-65 (2006).</li><li>Doyle, L. 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=A+multidrug+resistance+transporter+from+human+MCF-7+breast+cancer+cells.">A multidrug resistance transporter from human MCF-7 breast cancer cells.</a> Proc Natl Acad Sci U S A. 95 (26), 15665-15670 (1998).</li><li>Natarajan, K., Xie, Y., Baer, M. R., Ross, D. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+breast+cancer+resistance+protein+(BCRP/ABCG2)+in+cancer+drug+resistance.">Role of breast cancer resistance protein (BCRP/ABCG2) in cancer drug resistance.</a> Biochem Pharmacol. 83 (8), 1084-1103 (2012).</li><li>Qian, X., Cheng, Y. H., Mruk, D. D., Cheng, C. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Breast+cancer+resistance+protein+(Bcrp)+and+the+testis--an+unexpected+turn+of+events.">Breast cancer resistance protein (Bcrp) and the testis--an unexpected turn of events.</a> Asian J Androl. 15 (4), 455-460 (2013).</li><li>Xie, Y., 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=Bcrp1+transcription+in+mouse+testis+is+controlled+by+a+promoter+upstream+of+a+novel+first+exon+(E1U)+regulated+by+steroidogenic+factor-1.">Bcrp1 transcription in mouse testis is controlled by a promoter upstream of a novel first exon (E1U) regulated by steroidogenic factor-1.</a> Biochim Biophys Acta. 1829 (12), 1288-1299 (2013).</li><li>Maliepaard, M., 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=Subcellular+localization+and+distribution+of+the+breast+cancer+resistance+protein+transporter+in+normal+human+tissues.">Subcellular localization and distribution of the breast cancer resistance protein transporter in normal human tissues.</a> Cancer Res. 61 (8), 3458-3464 (2001).</li><li>Fetsch, P. 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=Localization+of+the+ABCG2+mitoxantrone+resistance-associated+protein+in+normal+tissues.">Localization of the ABCG2 mitoxantrone resistance-associated protein in normal tissues.</a> Cancer Lett. 235 (1), 84-92 (2006).</li><li>Cooray, H. C., Blackmore, C. G., Maskell, L., Barrand, 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=Localisation+of+breast+cancer+resistance+protein+in+microvessel+endothelium+of+human+brain.">Localisation of breast cancer resistance protein in microvessel endothelium of human brain.</a> Neuroreport. 13 (16), 2059-2063 (2002).</li><li>Kolwankar, D., Glover, D. D., Ware, J. A., Tracy, T. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+and+function+of+ABCB1+and+ABCG2+in+human+placental+tissue.">Expression and function of ABCB1 and ABCG2 in human placental tissue.</a> Drug Metab Dispos. 33 (4), 524-529 (2005).</li><li>Xiong, H., 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=ABCG2+is+upregulated+in+Alzheimer's+brain+with+cerebral+amyloid+angiopathy+and+may+act+as+a+gatekeeper+at+the+blood-brain+barrier+for+Abeta(1-40)+peptides.">ABCG2 is upregulated in Alzheimer's brain with cerebral amyloid angiopathy and may act as a gatekeeper at the blood-brain barrier for Abeta(1-40) peptides.</a> J Neurosci. 29 (1-40), 5463-5475 (2009).</li><li>Woodward, O. M., 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=Identification+of+a+urate+transporter,+ABCG2,+with+a+common+functional+polymorphism+causing+gout.">Identification of a urate transporter, ABCG2, with a common functional polymorphism causing gout.</a> Proc Natl Acad Sci U S A. 106 (25), 10338-10342 (2009).</li><li>Huls, M., 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=The+breast+cancer+resistance+protein+transporter+ABCG2+is+expressed+in+the+human+kidney+proximal+tubule+apical+membrane.">The breast cancer resistance protein transporter ABCG2 is expressed in the human kidney proximal tubule apical membrane.</a> Kidney Int. 73 (2), 220-225 (2008).</li><li>Nakanishi, 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=Novel+5'+untranslated+region+variants+of+BCRP+mRNA+are+differentially+expressed+in+drug-selected+cancer+cells+and+in+normal+human+tissues:+implications+for+drug+resistance,+tissue-specific+expression,+and+alternative+promoter+usage.">Novel 5' untranslated region variants of BCRP mRNA are differentially expressed in drug-selected cancer cells and in normal human tissues: implications for drug resistance, tissue-specific expression, and alternative promoter usage.</a> Cancer Res. 66 (10), 5007-5011 (2006).</li><li>Ayoubi, T. A., Van De Ven, W. J. <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+gene+expression+by+alternative+promoters.">Regulation of gene expression by alternative promoters.</a> FASEB J. 10 (4), 453-460 (1996).</li><li>Zong, Y., Zhou, S., Fatima, S., Sorrentino, B. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+of+mouse+Abcg2+mRNA+during+hematopoiesis+is+regulated+by+alternative+use+of+multiple+leader+exons+and+promoters.">Expression of mouse Abcg2 mRNA during hematopoiesis is regulated by alternative use of multiple leader exons and promoters.</a> J Biol Chem. 281 (40), 29625-29632 (2006).</li><li>Natarajan, K., 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=Identification+and+characterization+of+the+major+alternative+promoter+regulating+Bcrp1/Abcg2+expression+in+the+mouse+intestine.">Identification and characterization of the major alternative promoter regulating Bcrp1/Abcg2 expression in the mouse intestine.</a> Biochim Biophys Acta. 1809 (7), 295-305 (2011).</li><li>Promega. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Wizard&#174; SV Gel and PCR Clean-Up System - INSTRUCTIONS FOR USE OF PRODUCT. , (2009).</li><li>New_England_Biolabs. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Quick Ligation Kit Protocol - M2200S. , (2014).</li><li>Roche. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> XtremeGENE HP DNA Transfection Reagent Protocol - Manual version 1.0). , (2010).</li><li>Promega. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Quick Protocol for the use of the Dual-Luciferase Reporter Assay. , (2009).</li><li>Carninci, P., 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=The+transcriptional+landscape+of+the+mammalian+genome.">The transcriptional landscape of the mammalian genome.</a> Science. 309 (5740), 1559-1563 (2005).</li><li>VanBuren, V., 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=Assembly,+verification,+and+initial+annotation+of+the+NIA+mouse+7.4K+cDNA+clone+set.">Assembly, verification, and initial annotation of the NIA mouse 7.4K cDNA clone set.</a> Genome Res. 12 (12), 1999-2003 (2002).</li><li>Bonaldo, M. F., Lennon, G., Soares, M. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Normalization+and+subtraction:+two+approaches+to+facilitate+gene+discovery.">Normalization and subtraction: two approaches to facilitate gene discovery.</a> Genome Res. 6 (9), 791-806 (1996).</li><li>Okazaki, Y., 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=Analysis+of+the+mouse+transcriptome+based+on+functional+annotation+of+60,770+full-length+cDNAs.">Analysis of the mouse transcriptome based on functional annotation of 60,770 full-length cDNAs.</a> Nature. 420 (6915), 563-573 (2002).</li><li>Landry, J. R., Mager, D. L., Wilhelm, B. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complex+controls:+the+role+of+alternative+promoters+in+mammalian+genomes.">Complex controls: the role of alternative promoters in mammalian genomes.</a> Trends Genet. (11), 640-648 (2009).</li><li>Park, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ChIP-seq:+advantages+and+challenges+of+a+maturing+technology.">ChIP-seq: advantages and challenges of a maturing technology.</a> Nat Rev Genet. 10 (10), 669-680 (2009).</li><li>Bulun, S. E., 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+aromatase+expression+in+breast+cancer+tissue.">Regulation of aromatase expression in breast cancer tissue.</a> Ann N Y Acad Sci. 1155, 121-131 (2009).</li></ol>

The majority of the methods and representative results presented are described in previous work entitled &#34;Bcrp1 transcription in mouse testis is controlled by a promoter upstream of a novel first exon (E1U) regulated by steroidogenic factor-1,&#34; which was published in 20135. In addition to the representative results depicted here, the previous paper provided estimates of alternative first exon utilization using 5&#39;-RACE PCR and RT-PCR methodology. Furthermore, in-silico identificati...

More than half of human genes are regulated by alternative promoters1. Each alternative promoter can contain regulatory elements that may be different from those in other alternative promoters. The promoter(s) utilized in one tissue may differ from those used in another tissue. For example, it is possible that activation of a given signaling pathway may trigger the alternative promoter for a gene utilized in one tissue, yet have no effect on or repress a separate alternative promoter for the same gene that is utilized in another tissue.
Expression of the Bcrp1 gene is governed by alternative promoters. Bcrp1 is the murine orthologue of the human Breast Cancer Resistance Protein (BCRP) gene. BCRP is an ATP-binding cassette (ABC) transporter, formally designated ABCG22,3. As an apical plasma membrane protein, BCRP/Bcrp1 functions to efflux a wide variety of natural and xenobiotic substrates3,4. In humans and mice, BCRP/Bcrp1 is highly expressed in pharmacologically relevant organs such as liver (bile canaliculi), intestine, and kidney, as well as organs with blood-tissue barriers such as placenta, brain and testis2,5-12. Expression of BCRP/Bcrp1 in hematopoietic and other stem cells, including cancer stem cells, may confer resistance of these cells to xenobiotics and cancer chemotherapeutic drugs3.
In early work to understand the regulation of BCRP expression in normal and neoplastic cells, 5&#39; rapid amplification of cDNA ends (5&#39;-RACE) analysis of BCRP mRNA was performed to determine its exact transcriptional start site13. Not only were multiple transcriptional start sites found; also encountered were three alternative forms of the first exon, which in BCRP is untranslated. These alternative first exons&#160;&#8212; designated E1a, E1b, E1c &#8212; were expressed differently in a variety of human tissues. Two additional first exon variants were discovered in a BLAST search of the human EST database using the second exon of BCRP13. Four matches revealed a first exon &#62;70 kb upstream from exon 2 which were designated E1u; four other matches revealed BCRP mRNA that lacked a first exon entirely, which were designated E1-13. The presence of alternative leader exons is considered to be a manifestation of alternative promoter usage14.
In mice, four alternative first exons of Bcrp1 are described that may correspond to alternative promoters that govern Bcrp1 transcription in different mouse tissues; these exons/promoters are designated E1U, E1A, E1B and E1C, and are located approximately 70, 58, 15, and 5 kb upstream from Bcrp1 exon 25,15. The E1A mRNA isoform was found to be predominant in murine hematopoietic stem cells, heart, lung, spleen, and brain, whereas the E1B isoform was expressed in mouse intestine, fetal liver cells, and erythroid precursor cells in bone marrow5,15. The promoter upstream from E1B was shown to be the major alternative promoter governing Bcrp1 transcription in mouse intestine, regulated at least in part, by phospho-cyclic-AMP response element binding protein (p-CREB) and a CREB response element unique to that alternative Bcrp1 promoter16. The E1C mRNA isoform is predominantly expressed in adult murine liver and kidney5. The E1U isoform is undetectable in most tissues tested except for murine testis, where it is the predominant isoform expressed5. Bcrp1 expressed in rat testes is found in both somatic (endothelial tight junctions, peritubular myoid cells, and Sertoli cells) and germ cells (in the seminiferous endothelium, where it may protect late-stage spermatids4). The region upstream from E1U contains a functional response element for steroidogenic factor-1 (SF-1)5. Bcrp1 mRNA and protein are markedly reduced in the testes of Sertoli cell-specific SF-1 knockout mice, suggesting that Bcrp1 expression in murine Sertoli cells is controlled by SF-15.
The protocols presented detail methods to detect alternative first exons of Bcrp1 in-silico, and to establish luciferase-based reporter assays for putative promoters upstream from the alternative first exons identified.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>COMMERCIAL BIOLOGIC MATERIALS AND KITS:</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>First Choice RLM-RACE kit</td>
			<td>Ambion Inc., Austin, TX, currently available through Life Technologies</td>
			<td>AM1700</td>
			<td>5&#39;-RACE PCR kit</td>
		</tr>
		<tr>
			<td>TOPO TA cloning kit&#160;</td>
			<td>Life Technologies</td>
			<td>K450001</td>
			<td>This kit contains the TOP10 chemically competent E. coli bacteria.</td>
		</tr>
		<tr>
			<td>T4 DNA ligase quick ligation kit</td>
			<td>New England Biolabs</td>
			<td>M2200</td>
			<td></td>
		</tr>
		<tr>
			<td>Faststart high-fidelity Taq- DNA polymerase</td>
			<td>Sigma-Aldrich/Roche</td>
			<td>3553400001/RMB-4738284001&#160;</td>
			<td>Contains a high-fidelity Taq polymerase enzyme blend</td>
		</tr>
		<tr>
			<td>XtremeGENE HP DNA transfection reagent</td>
			<td>Roche</td>
			<td>6366236001</td>
			<td></td>
		</tr>
		<tr>
			<td>Dual-luciferase reporter assay kit</td>
			<td>Promega</td>
			<td>E1910</td>
			<td>Includes the pGL3-basic empty reporter vector (firefly luciferase), pRLTK renilla luciferase expressing vector, and other control vectors.</td>
		</tr>
		<tr>
			<td>QIAprep</td>
			<td>Qiagen</td>
			<td>27104</td>
			<td>For plasmid miniprep - isolation and purification of plasmid DNA from bacterial colonies</td>
		</tr>
		<tr>
			<td>pCR2.1 vector</td>
			<td>part of the TOPO TA cloning kit</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>pGL3-basic luciferase containing vector</td>
			<td>Promega</td>
			<td>E1751</td>
			<td></td>
		</tr>
		<tr>
			<td>pRL-TK Renilla luciferase expressing vector</td>
			<td>Promega</td>
			<td>E2241</td>
			<td></td>
		</tr>
		<tr>
			<td>Bacterial artificial chromosome</td>
			<td>BACPAC Resources Center, Children&#8217;s Hospital Oakland Research Institute, Oakland, CA</td>
			<td>RP23-285A12 and RP24-314E24</td>
			<td>http://bacpac.chori.org/clones.htm</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company&#160;</td>
			<td>Catalog Number&#160;</td>
			<td>Comments</td>
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			<td>REAGENTS/CHEMICALS/MEDIA/SUPPLIES</td>
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			<td>TRIzol</td>
			<td>Life Technologies</td>
			<td>15596026</td>
			<td></td>
		</tr>
		<tr>
			<td>Wizard&#174; SV Gel and PCR Clean-Up System&#160;</td>
			<td>Promega</td>
			<td>A9281</td>
			<td>Useful for purifying PCR products following digestion with restriction endonucleases</td>
		</tr>
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			<td>CRYOVIALS</td>
			<td>Denville Scientific</td>
			<td>V9012</td>
			<td></td>
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			<td>Name</td>
			<td>Company&#160;</td>
			<td>Catalog Number&#160;</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>SOFTWARE:</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ensembl software</td>
			<td>Ensembl project</td>
			<td>http://Ensembl.org&#160;</td>
			<td>The Ensembl project produces genome databases for vertebrates and other eukaryotic species, and makes this information freely available online.</td>
		</tr>
		<tr>
			<td>Blast software</td>
			<td>NCBI</td>
			<td>http://blast.ncbi.nlm.nih.gov/Blast.cgi?CMD= 
			Web&#38;PAGE_TYPE=BlastHome</td>
			<td></td>
		</tr>
		<tr>
			<td>Primer 3 software</td>
			<td>Simgene</td>
			<td>http://simgene.com/Primer3</td>
			<td>Useful for designing primers for 5&#39;-RACE PCR</td>
		</tr>
		<tr>
			<td>NCBI Nucleotide database</td>
			<td>NCBI</td>
			<td>http://www.ncbi.nlm.nih.gov/nucleotide/</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company&#160;</td>
			<td>Catalog Number&#160;</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>CELL LINES:</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>TM4 murine Sertoli cells</td>
			<td>ATCC, Manassas, Virginia</td>
			<td>CRL-1715&#8482;</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company&#160;</td>
			<td>Catalog Number&#160;</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>INSTRUMENTS:</td>
			<td></td>
			<td></td>
			<td></td>
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			<td>Luminometer</td>
			<td>Turner Biosystems</td>
			<td>TD-20/20</td>
			<td>This is a relatively inexpensive, manually operated luminometer. Automated systems are also available from the same manufacturer that utilize 96 well plates.</td>
		</tr>
		<tr>
			<td>NanoDrop spectrophotometers</td>
			<td>Thermo Scientific, Inc.</td>
			<td>NanoDrop 2000</td>
			<td>Spectrophotometer can use very small quantities of sample</td>
		</tr>
		<tr>
			<td>DU 800 UV/VIS spectrophotometer and Nucleic Acid Analysis II software</td>
			<td>BeckmanCoulter Inc, Fullerton, CA</td>
			<td>DU 800</td>
			<td></td>
		</tr>
	</tbody>
</table>

methods to discover alternative promoter usage and transcriptional regulation of murine bcrp1

Gene expression in different tissues is often controlled by alternative promoters that result in the synthesis of mRNA with unique &#8212; usually untranslated &#8212; first exons. Bcrp1 (Abcg2), the murine orthologue of the ABC transporter Breast Cancer Resistance Protein (BCRP, ABCG2), has at least four alternative promoters that are designated by the corresponding four alternative first exons produced: E1U, E1A, E1B, and E1C. Herein, in-silico protocols are presented to predict alternative promoter usage for Bcrp1. Furthermore, reporter assay methods are described to produce reporter constructs for alternative promoters and to determine the functionality of putative promoters upstream of the alternative first exons that are identified.

Identification of Bcrp1 alternative promoter utilization in mouse testis by analysis of leader exons
When the EST database at NCBI was probed (April 2015) using the steps outlined in Protocol 1, the ESTs found that were contiguous with the 5&#39; end of exon 2 in Bcrp1 mRNA are shown in Table 1, along with their position in genomic DNA relative...

Watch this Scientific Journal Video about Methods to Discover Alternative Promoter Usage and Transcriptional Regulation of Murine Bcrp1 at JoVE.com

Methods to Discover Alternative Promoter Usage and Transcriptional Regulation of Murine Bcrp1

With the murine ABC transporter Bcrp1 (Abcg2) as an example, in-silico protocols are presented to detect alternative promoter usage in genes expressed in mouse tissues, and to evaluate the functionality of the alternative promoters identified using reporter assays.

Gene expression in different tissues is often controlled by alternative promoters that result in the synthesis of mRNA with unique &#8212; usually ...

The overall goal of this set of protocols is to detect alternative first exons in the mRNA of a gene such as Bcrp1 and to establish luciferase-based reporter assays for the putative promoters upstream of the alternative identified first exons. The in-silico methods used can help answer key questions in the transcription and regulation field such as how mRNA expression is controlled in different tissues. The main advantage of this technique is that it uses publicly available genetic data to identify alterative first exons in the mRNA of gene of interest, which implies alternative promoter usage.This method that prepares report constructs and conducts reporter assays can help answer key questions in the gene regulatory field such as the functional activity of a putative alternative promoters. To begin this procedure, obtain the sequence for mouse Bcrp1 exon 2 by inputting the mRNA reference sequence ID into the search window of the Ensembl genome browser and click Go.Next, select a full length sequence that contains 16 exons. Click the Download sequence option.Then, choose the FASTA format and click Preview. In the next screen, copy the preview sequence of exon 2 into the clipboard. Navigate to the blast homepage on the NCBI website.Select Mouse genome. Paste the exon 2 sequence from the clipboard into the query box. After that, select ESTs from the Database drop down.Optimize it for Highly similar sequences and then choose BLAST. When the BLAST run is complete, the results page will appear. Under the Descriptions subheading of the results page, select All, then Download, followed by FASTA in the drop down, and then choose Continue.A txt file will appear. Open and copy the entire file into the clipboard. To identify the location of the EST sequence that is five prime to exon 2 in the Bcrp1 gene, on the BLAST homepage under the Specialized BLAST subheading, select Align two sequences using BLAST.Paste the text file from the clipboard into the query box and enter 372099104 in the Subject Sequence box. Optimize it for Highly similar sequences under Program Selection and run BLAST. Once the results window appears, view the alignments graphically by clicking Graphics in the Alignments window.Use the right and left arrows and zoom to focus on Bcrp1/ABCG2 and the sequence alignments. Then, save the sequence alignments by selecting All in the Descriptions box. Under the Download drop down, select Hit Table and then click Continue.As the position of the five prime end of exon 2 corresponds to the nucleotide 58, 655, 638 in the chromosome six contig, designate this as plus one and then calculate the position of the partial sequences of each EST five prime to 58, 655, 638. A critical step in this procedure is the prediction of multiple first exons. The alternative promoters are hence identified here.Using the sequence of E1U obtained from the EST database, designate the first five prime nucleotide of E1U as plus one. Obtain a back clone of mouse chromosome six that contains the Bcrp1/ABCG2 gene sequence and the sequence at least 100 kilobases upstream of the Bcrp1/ABCG2 gene. Then, identify a suitable reporter vector, such as the luciferase reporter plasmid pGL3-Basic.Determine the multiple cloning sites in the reporter vector. KpnI, SacI, MluI, NheI, SmaI, XhoI, BglII, and HindIII are the restriction endonucleae sites in the multiple cloning site of the pGL3-Basic vector in the five prime to three prime orientation. Next, select the two kilobase region upstream of the E1U exon and paste the sequence in the DNA5 followed by running the program.The details of the single and multiple digestion sites will be displayed. After that, compare the list of digestion sites on the E1U region with the MCS on the pGL3-Basic vector in an excel sheet. Subsequently, prepare forward and reverse primers for PCR that contain restriction endonucleae sites using commercial gene primer synthesis services or primer selection software.Select a forward primer located about two kilobases upstream of the E1U sequence and a reverse primer within the E1U sequence. Then, amplify the E1U genomic region using these primers with PCR 01 to one microgram of Bak and PCR Master Mix containing high fidelity taq polymerase. Afterward, verify the length of the amplified PCR product by comparing it against a one kilobase DNA ladder using 0.8%TAE agarose gel electrophoresis.Afterward, digest the obtained PCR product and the pGL3-Basic vector using restriction endonucleases specific for restriction digestion sites introduced into the forward and reverse primers. Then, verify the digestion of the PCR product using agarose gel electrophoresis. Cut the digested vector DNA and the two kilobase PCR band from the agarose gel.Next, extract the digested vector DNA and the two kilobase PCR band from the gel slices using a commercial SV gel and PCR clean-up systems kit. Measure the concentration of the purified PCR product and the purified vector using UV spectrometry. Subsequently, prepare the E1U reporter construct by ligating the purified restriction enzyme digested PCR product and the pGL3-Basic firefly luciferase reporter vector using the T4 DNA ligase quick ligation kit thereby producing the E1U reporter construct named pGL3 E1U.In this step, culture the TM4 cells in 24-well plates at an initial density of 200, 000 cells per well. Six hours after placing the cells in culture, transfect the cells with 0.2 micrograms of MP pGL3-Basic vector or 0.2 micrograms of pGL3 vector along with four nanograms of pRL-TK as an internal control. Thirty hours following transfection, remove the growth media from the transfected cells.Wash the cells with PBS, then remove the wash solution. After that, measure the firefly and Renilla luciferase activity using a commercial kit. Express the activity for each tube as the ratio of the firefly luciferase activity divided by the internal control.This step confirms the functional activity of the testis specific promoter. Here is the reporter assay for Bcrp1 promoters E1U, E1A, E1B, and E1C in bulbs these are totally cell-derived TM4 cells. Data are expressed as the luminescence of firefly luciferase normalized to that of Renilla luciferase.The asterisk indicates a significant difference from the MP pGL3 vector control. This graph shows the effects of mutation of the SF-1 response element in the Bcrp1 E1U reporter construct on luciferase activity. Bcrp1 reporter constructs with a putative SF-1 binding region were transfected into TM4 cells with and without the enforced expression of SF-1.In the figure, a denotes a significant difference from the empty vector pGL3 control;b signifies a statistically significant difference compared to the E1U promoter construct in the vector transfected cells. While attempting this procedure, it's important to remember to select an appropriate cell line for the reporter assay. The cell line should express the gene of interest under the control of the promoter in the reporter construct.Following this procedure, other methods, such as quantitative RT-PCR can be performed in order to facilitate evaluation of alternative promoter usage in multiple tissue samples. After watching this video, you should have a good understanding of how to predict alternative promoter usage for a gene of interest and to determine the functionality of that promoter.

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JoVE Journal

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8.0K visualizações.  University of Maryland School of Medicine. The overall goal of this set of protocols is to detect alternative first exons in the mRNA of a gene such as Bcrp1 and to establish luciferase-based reporter assays for the putative promoters upstream of the alternative identified first exons. The in-silico methods used can help answer key questions in the transcription and regulation field such as how mRNA expression is controlled in different tissues. The main advantage of this technique is that it uses publicly available genetic data to id...