Study of Rest As A Negative Regulator of P16Ink4A

<p><strong>STUDY OF REST AS A NEGATIVE REGULATOR OF P16^INK4A</strong><strong> </strong></p> <p><strong>Monica Gireud, B.S.</strong></p> <p><strong>Thesis Advisor: Vidya Gopalakrishnan, Ph.D.</strong></p> <p>The<em> RE1</em> Silencing Transcription Factor (REST) is a negative regulator of neuronal differentiation. It is expressed ubiquitously in early embryos, but downregulated in neural progenitors concomitant with onset of neuronal differentiation in these cells. REST has been widely studied as a negative regulator of neuronal differentiation genes. Our recent work identified a novel role for REST in control of cell proliferation. However, the underlying molecular mechanism(s) are not known and is a focus of the current thesis project. Here, we provide evidence that REST signaling controls the expression of the cyclin-dependent kinase inhibitor, p16^Ink4a, a negative regulator of the cell cycle and passage through G1. We determined that REST expression in the proliferating granule progenitors of the cerebellum and its lack of expression in the differentiated neurons is reciprocally correlated with that of p16^Ink4a. Decline in REST levels in differentiating primary and neural stem cells immortalized with v-myc (NSC-M) granule progenitors <em>in vitro</em> was also associated with upregulation of p16^Ink4a expression. Conversely, constitutive human REST transgene expression in NSC-M cells (NSC-MRs) blocked p16^{Ink4<em> </em>}upregulation, even under neuronal differentiation conditions. However, the lack of a consensus REST DNA binding <em>RE1 </em>element in the regulatory regions of <em>p16^Ink4a</em> locus suggested an indirect regulation of p16^Ink4a by REST. Based on work from other groups that showed repression of <em>p16^Ink4a</em> transcription by the polycomb protein Bmi-1, and its negative regulation by <em>microRNA-203</em> (<em>miR-203</em>) and our identification of a <em>RE1 </em>element in the downstream regulatory region of <em>miR-203, </em>we asked if the p16^Ink4a expression was controlled by REST through a series of negative regulatory events involving <em>miR-203</em> and Bmi-1. We observed that Bmi1 -expression mirrored that of REST and inversely correlated with that of <em>miR-203</em> in the postnatal cerebellum and <em>in vitro</em> differentiated granule and NSC-M progenitors. In contrast, forced <em>REST</em> transgene expression in NSC-MR cells abrogated the decrease in Bmi-1 levels and elevation in <em>miR-203</em> expression. Significant REST binding to the <em>miR-203</em> <em>RE1</em> element was also observed in NSC-M cells, indicating that REST had the potential to directly regulate <em>miR-203</em> expression. In conclusion, our studies suggest a role for REST in control of cell cycle transit in neural progenitors through negative regulation of <em>p16^Ink4a</em>. Further validation of these results in REST knockout mice is needed, and is ongoing.</p> <p><strong> </strong></p>

Name thesis:degree_name

Masters of Science (MS)

Level thesis:degree_level

Thesis (MS)

Year dc:date.available

2011

Author dc:creator

• Gireud, Monica B

Contributors dc:contributor

• Vidya Gopalakrishnan, Ph.D.
• Dennis Hughes, M.D., Ph.D.
• George Calin, M.D., Ph.D.

• REST
• p16
• miR-203
• Bmi-1
• Cell proliferation
• Biology
• Cancer Biology
• Developmental Biology
• Molecular and Cellular Neuroscience

Repository record dc:identifier

https://digitalcommons.library.tmc.edu/utgsbs_dissertations/174

OAI identifier oai:identifier

oai:digitalcommons.library.tmc.edu:utgsbs_dissertations-1204