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Characterizing and Alleviating Androgen Receptor-Mediated Transcriptional Repression of Tumor Suppressor Gene GPER1

McDermott, Austin
http://orcid.org/0000-0003-0246-037X
http://rave.ohiolink.edu/etdc/view?acc_num=ucin164976208384905

Abstract Details

2022, PhD, University of Cincinnati, Medicine: Toxicology (Environmental Health).
The focus of this dissertation is the characterization of Androgen Receptor (AR)-mediated transcriptional repression of GPER1 gene in prostate cancer (PCa). Although inhibiting AR signaling remains central to the treatment of prostate cancer, growing evidence indicates current androgen deprivation therapies (ADT) aid in the development of castration resistant prostate cancer (CRPC) and resistance to treatment. Many of the genes responsible for PCa progression are repressed by AR, and AR-mediated transcriptional repression is vastly understudied compared to AR-mediated gene activation. Here we use the recently described potential PCa tumor suppressor GPER1 to investigate mechanisms of AR-mediated gene transcriptional repression. We found that despite not binding to the promoters of GPER1 in LNCaP prostate cancer cells, the androgen-activated AR interacted with the Sp1 and Sp3 transcription factors to prevent their binding to their DNA-binding sites and transactivation of the GPER1 promoters. Additionally, we show that AR inhibited GPER1 transcription by binding to an androgen response element (ARE) adjacent to an enhancer (termed GPER1-Enh) ~3.6kb downstream of the transcription termination site of GPER1. Interestingly, AR binding to the ARE subsequently upregulated an antisense RNA transcript we termed AS-GP. Finally, we show that low dose (5 nM) mithramycin (MTM), commonly used in inhibit GC- rich sequence binding proteins such as Sp1 and Sp3, was able to effectively alleviate transcriptional repression of GPER1 by AR although it failed to also upregulate GPER1 protein expression indicating additional mechanisms were at play at the translational or protein stability level. Although high concentrations of MTM (50-200nM) repress Sp1- and Sp3- dependent gene expression, low concentrations of MTM (5-10 nM) have been reported induce re-expression of silenced genes, such as GPER1 in our experiments, through repression of DNA Methyltransferase 1 (DNMT1) protein. Chapter One gives the necessary background to understand the rationale behind this dissertation research. Chapter Two details how the AR represses the GPER1 gene transcription by preventing Sp1 and Sp3 from binding to the GPER1 promoters. Chapter Three presents preliminary evidence that the AR represses GPER1 by binding to a downstream enhancer (GPER1-Enh) while simultaneously inducing transcription of an antisense lncRNA (AS-GP). Chapter Four demonstrates that a low dose of MTM is an effective alleviator of AR-mediated transcriptional repression of GPER1. Because low dose MTM inhibits DNMT expression, the GPER1 repression by MTM might be due to repressing expression of DNA methyltransferases DNMT1, DNMT3a, and DNMT3b expression. This is the first report of MTM inhibiting either DNMT3a or DNMT3b protein expression in prostate cancer cells. Additional research is necessary to uncover how MTM alleviates AR-mediated transcriptional repression as Decitabine also inhibited these same DNA Methyltransferases and was not as effective at alleviating AR-mediated transcriptional repression. Finally, Chapter Five summarizes the main findings of this dissertation, provides overall conclusions, and indicates potential future directions. Overall, these results expand our mechanistic understanding of AR-mediated gene transcription repression and highlight the potential of using low dose MTM to induce the expression of silenced tumor suppressor genes for combinatory cancer therapies.
Susan Kasper, Ph.D. (Committee Member)
Divaker Choubey, Ph.D. (Committee Member)
Ying Xia, Ph.D. (Committee Member)
Yuya Ogawa, Ph.D. (Committee Member)
KyoungHyun Kim, Ph.D. (Committee Member)
163 p.
Biology
GPER1; Sp1; Sp3; Androgen Receptor; Mithramycin

Recommended Citations

Citations

  • McDermott, A. (2022). Characterizing and Alleviating Androgen Receptor-Mediated Transcriptional Repression of Tumor Suppressor Gene GPER1 [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin164976208384905

    APA Style (7th edition)

  • McDermott, Austin. Characterizing and Alleviating Androgen Receptor-Mediated Transcriptional Repression of Tumor Suppressor Gene GPER1. 2022. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin164976208384905.

    MLA Style (8th edition)

  • McDermott, Austin. "Characterizing and Alleviating Androgen Receptor-Mediated Transcriptional Repression of Tumor Suppressor Gene GPER1." Doctoral dissertation, University of Cincinnati, 2022. http://rave.ohiolink.edu/etdc/view?acc_num=ucin164976208384905

    Chicago Manual of Style (17th edition)

ucin164976208384905
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© 2022, some rights reserved.Creative Commons License Characterizing and Alleviating Androgen Receptor-Mediated Transcriptional Repression of Tumor Suppressor Gene GPER1 by Austin McDermott is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.