Undergraduate Honors Theses

Thesis Defended

Spring 2015

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Molecular, Cellular, & Developmental Biology

First Advisor

Dr. Joaquín Espinosa

Second Advisor

Dr. Ravinder Singh

Third Advisor

Dr. Dylan Taajes

Abstract

p53 is a tumor suppressor protein which orchestrates cell cycle arrest or apoptosis to prevent the hyperproliferation of cells which could lead to cancer. However, when p53 is inactivated, which happens in over 50% of cancers, it fails to induce PUMA, a potent apoptotic protein. Loss of PUMA makes cancer cells less likely to undergo apoptosis upon stress stimuli. Recent GRO-seq data revealed unique antisense transcription initiated 6kb into the PUMA locus, creating a small noncoding RNA transcript dubbed BAIT (BBC3 antisense intragenic transcript). This project focused on understanding the expression and function of BAIT, which we hypothesized could modulate the expression of the sense PUMA transcript. Using a luciferase reporter vector we showed that the proximal TATA box near the transcription start site for BAIT is necessary to drive its expression. We found that BAIT is expressed in different cell types and BAIT levels fluctuate in response to different stimuli. Surprisingly, we demonstrated BAIT expression is independent of p53, as elevated levels were observed in HCT116 p53 null cells. Finally, we observed that BAIT expression decreased upon activation of p53 by Nutlin as compared to basal conditions, and when BAIT is knocked down, the predominant PUMA transcript variant decreased. This provides the foundation for future studies to determine a mechanism for how BAIT contributes to the regulation of PUMA expression, which could illuminate strategies to induce PUMA expression and apoptosis in tumors with inactive p53.

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