Transcriptional and Post-Translational Mechanisms Contribute to Maintenance of Rest In Neural Tumors

<p>The <em>RE-1</em> silencing transcription factor (REST) is an important regulator of normal nervous system development. It negatively regulates neuronal lineage specification in neural progenitors by binding to its consensus <em>RE-1</em> element(s) located in the regulatory region of its target neuronal differentiation genes. The developmentally coordinated down-regulation of REST mRNA and protein in neural progenitors triggers terminal neurogenesis.</p> <p>REST is overexpressed in pediatric neural tumors such as medulloblastoma and neuroblastoma and is associated with poor neuronal differentiation. High REST protein correlate with poor prognosis for patients with medulloblastoma, however similar studies have not been done with neuroblastoma patients. Mechanism(s) underlying elevated REST<em> </em>levels medulloblastoma and neuroblastoma are unclear, and is the focus of this thesis project.</p> <p>We discovered that transcriptional and post-translational mechanisms govern REST mis-regulation in medulloblastoma and neuroblastoma. In medulloblastoma, <em>REST</em> transcript is aberrantly elevated in a subset of patient samples. Using loss of function and gain of function experiments, we provide evidence that the Hairy Enhancer of Split (HES1) protein represses <em>REST</em> transcription in medulloblastoma cell lines, modulates the expression of neuronal differentiation genes, and alters the survival potential of these cells <em>in vitro</em>.</p> <p>We also show that REST directly represses its own expression in an auto-regulatory feedback loop. Interestingly, our studies identified a novel interaction between REST and HES1. We also observed their co-occupancy at the <em>RE-1</em> sites, thereby suggesting potential for co-regulation of <em>REST</em> expression.</p> <p>Our pharmacological studies in neuroblastoma using retinoic acid revealed that REST levels are controlled by transcriptional and post-transcriptional mechanisms. Post-transcriptional mechanisms are mediated by modulation of E3 ligase or REST, SCF^β-TRCP, and contribute to resistance of some cells to retinoic acid treatment.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation (PhD)

Year dc:date.available

2012

Author dc:creator

• Singh, Akanksha

Contributors dc:contributor

• Vidya Gopalakrishnan, Ph.D.
• Jaroslaw Aronowski, Ph.D.
• Andrew Bean, Ph.D.

• REST/NRSF
• transcription
• regulation
• SCFβ-TRCP
• retinoic acid
• medulloblastoma
• neuroblastoma
• Medicine and Health Sciences

Repository record dc:identifier

https://digitalcommons.library.tmc.edu/utgsbs_dissertations/289

OAI identifier oai:identifier

oai:digitalcommons.library.tmc.edu:utgsbs_dissertations-1323