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Degree

Doctor of Philosophy, Case Western Reserve University, Pharmacology, 2006.

Abstract

A “molecular switchboard”-Lysine modifications and their impact on transcription Abstract by ZHENG GANG Post-translational modifications greatly increase the complexity of the proteome in eukaryotic cells. Multi-site modification on a protein resembles a dynamic 'molecular switchboard' and transduces signals to and from different pathways. We are interested in the regulation and the functional roles of lysine modifications, especially their impact on transcription. ZNF76 (Zinc Finger protein 76) was found to be a general transcriptional repressor targeting TATA-Binding Protein (TBP). Interaction with ZNF76 prevents TBP from being recruited to the target promoters. Moreover, the interaction between ZNF76 and PIAS1 (Protein Inhibitor for Activated STAT1), an E3 ligase in sumoylation, leads to sumoylation of ZNF76. Interestingly, a sumoylation site of ZNF76, K411, lies in a critical region for TBP interaction, and sumoylation negatively regulates ZNF76-TBP interaction. In addition, we found that acetylation and alternative splicing of ZNF76 also regulate its interaction with TBP, suggesting multiple mechanisms exist to regulate ZNF76-TBP interaction. PLAG1 (Pleomorphic Adenoma Gene 1) and PLAGL2 (PLAG Like Gene 2) are oncoproteins involved in various malignancies. The regulatory mechanisms of their transactivation remain unknown. We found that sumoylation in the middle regions of PLAG1 and PLAGL2 represses their transactivation. One of the possible mechanisms for sumoylation-mediated repression is the change in protein subnuclear localization. Moreover, acetylation activates, while deacetylation represses, transactivation of PLAG1 and PLAGL2. Mutations of the sumoylation sites greatly impair the transforming abilities of PLAG1 and PLAGL2. Taken together, sumoylation and acetylation play opposite roles in regulating the transactivation of PLAG1 and PLAGL2. Pirh2 (P53 Inducible Ring-H2 protein) is one of the E3 ubiquitin ligases for p53. It was found to form dimers involving both N- and C-terminus. Furthermore, we demonstrated that the Pirh2 dimer formation promotes its interaction with both p53 and PLAGL2. Given the importance of Pirh2 in regulating p53 stability, its dimer may be a valuable therapeutic target in treating Pirh2-overexpression malignancies. In summary, we studied the molecular mechanisms by which lysine modifications, such as sumoylation, acetylation and ubiquitination, regulate transcription factors, including ZNF76, PLAG1, PLAGL2 and p53. Our study may provide novel approaches to modulate their activities in associated diseases, Such as AML (Acute Myeloid Leukemia) which has PLAG1 or PLAGL2 overexpression, or lung cancer which has Pirh2 overexpression.

Keywords

PLAG1 PLAGL2 ZNF76 P53 TBP Ubiquitination Sumoylation Acetylation transcriptional repression

Advisor

Yu-Chung Yang

Pages

246p.

Document number: case1131636831
Permalink: http://rave.ohiolink.edu/etdc/view?acc_num=case1131636831

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