Date of Degree

2-2016

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biology

Advisor(s)

Diego Loayza

David Foster

Committee Members

David Foster

Jill Bargonetti

Anjana Saxena

Patricia Cortes

Subject Categories

Cancer Biology | Cell Biology | Molecular Genetics

Keywords

DNA damage response, Replication Protein A, ATM and Rad3-related (ATR) kinase, Checkpoint kinase 1

Abstract

LIM proteins constitute a superfamily characterized by the presence of specialized domains called LIM. LIM domain is a unique double-zinc finger motif found in a variety of proteins and is mainly involved in protein-protein interactions. Previous work has implicated that members of the Zyxin subfamily of LIM proteins, namely TRIP6 and LPP are involved in the repression of the DNA damage response (DDR) at telomeres. We further explore if another member from this family has an influence on DDR prevention in the cells. Here, we describe a novel role for Ajuba, a Zyxin family LIM protein, in repressing inappropriate activation of ATR kinase mediated DDR. We found that depletion of Ajuba led to a decrease in cell proliferation, apparent delay in the cell cycle, accompanied with increased phosphorylation of Retinoblastoma protein (Rb). We detect that reduction of Ajuba leads to Chk1 phosphorylation, indicative of ATR activation in cells. We also observe induction of p53 and cell death by apoptosis in the Ajuba depleted cells. The phenotypic effects of Ajuba depletion are observed in cancer as well as in non- cancer cells types. Ajuba could be found in a complex with replication protein A (RPA). Ajuba depletion led to RPA phosphorylation, which is known to be an early event in ATR activation. We propose that Ajuba exerts its function through its interaction with the RPA complex, preventing undesirable RPA phosphorylation in the absence of exogenous insults, and thereby repressing an inappropriate ATR activation.

 
 

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