Date of Graduation

Fall 12-8-2014

Document Type

Thesis

Degree Name

Master of Science in Biology

College/School

College of Arts and Sciences

Department/Program

Biology

First Advisor

Christina Tzagarakis-Foster

Second Advisor

James Sikes

Third Advisor

Mary Jane Niles

Abstract

DAX-1 is a member of the Nuclear Hormone Receptor superfamily and acts as a transcriptional repressor. DAX-1 plays an important role in the development of adrenal and gonadal tissues. In addition to its role in normal cell development and differentiation, DAX-1 appears to have some influence on the progression of cancer. This work aims to examine the role of DAX-1 in regulation of proliferation in breast cancer. In our study, we have expressed DAX-1 in a DAX-1 deficient breast cancer cell line as well as knocked down DAX-1 expression in normal DAX-1 positive breast cells. Through these experiments, we were able to identify DAX-1 target genes and effect a change in proliferation rate.

In an effort to better understand DAX-1 function both in normal and disease states we also examined one type of posttranslational modification, SUMOylation. SUMOylation involves the addition of the small polypeptide conjugate SUMO (Small Ubiquitin-like Modifier) to proteins. SUMOylation can have a variety of effects on target proteins including changes in localization, protein-protein interaction, interaction with DNA, and in some cases stabilization of the target protein. SUMOylation of nuclear hormone receptors can have profound effects on their function. To study the effects of SUMOylation on DAX-1, the overall SUMOylation status of DAX-1 in mammalian cell lines was determined. It was found that DAX-1 is SUMOylated in several cell lines, both normal and carcinoma cells. Mutations were made in putative SUMOylation sites within the DAX-1 gene. Mutants were then transfected and assayed for changes in gene expression and activity. It was determined that mutating either of two putative SUMOylation sites led to a loss of DAX-1 repressive function when compared to wild-type DAX-1.

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