ELUCIDATION OF REGULATORY MECHANISMS OF TRANSCRIPTION AND COUPLED mRNA EXPORT

Author

Geetha Durairaj, Southern Illinois University CarbondaleFollow

Date of Award

12-1-2013

Degree Name

Doctor of Philosophy

Department

Molecular Biology, Microbiology and Biochemistry

First Advisor

Bhaumik, Sukesh

Abstract

Gene expression is driven by the combined actions of numerous proteins that act in a regulated fashion. One of the central processes in gene expression is the export of the synthesized mRNA from nucleus to the cytoplasm where it gets translated into proteins. This journey of mRNA is mediated by numerous factors and receptors that get loaded onto the transcribing mRNA in a co-transcriptional fashion. Mutations of many export factors are directly linked to various diseases, thereby stressing the importance of tight regulation in mRNA export. Thus, one of my thesis aims had been focused on understanding the regulatory mechanisms of mRNA export by an F-box protein, Mdm30. Two recent studies have implicated the role of ubiquitylation in mRNA export via HECT domain-containing E3 ligases like Tom1 and Rsp5. My work has revealed the role of an F-box protein (Mdm30) component of RING domain-containing SCF (Skp-Cullin-F-box) family of E3 ligases in mRNA export, thereby implicating the role of ubiquitylation in export via non-HECT E3 ligase for the first time. My results show that Mdm30 ubiquitylates Sub2, an integral component of the TREX (Transcription/export) complex which is involved in mediating proper nuclear export of mRNA. In addition to its role in mRNA export, TREX complex is also involved in transcription. Hence, during the course of my research, I have also worked on understanding the regulation of transcription. Especially, we focused on the role of Sus1, a component of TREX-2 complex, in regulation of transcription. Further, since sense transcription and coupled mRNA export is likely to be regulated by antisense transcripts or antisense transcription, it is important to understand how antisense transcription is regulated to ultimately control mRNA export. Therefore, I have also worked on understanding the regulation of antisense transcription. Our results show that activator and GTFs (general transcription factors) are involved in antisense transcription initiation. However, antisense transcription is initiated independently of the sense transcription. Collectively, the outcomes of my thesis research provide important insights on the regulatory mechanisms of transcription and coupled mRNA export.