Date of Award

Summer 8-2013

Degree Type

Thesis-Restricted

Degree Name

M.S.

Degree Program

Biological Sciences

Department

Biological Sciences

Major Professor

Liu Zhengchang

Second Advisor

Wendy Schluchter

Third Advisor

Mary Clancy

Abstract

Nutrient availability regulates eukaryotic cell growth. This study focuses on two signaling pathways, involved in sensing amino acids and carbon sources, which allow cells to respond appropriately to their presence. The first part of this study shows that Ssy1, a plasma membrane localized sensor in the Ssy1-Ptr3-Ssy5 (SPS) amino acid sensing pathway, can detect 19 common L-amino acids with different potencies and affinities based on the physiochemical structure of amino acids. Substituents around alpha carbon are critical for amino acid sensing by Ssy1. Furthermore, a high concentration of cysteine is toxic to cells. Inactivation of SPS signaling confers resistance to cysteine. The second part focuses on the regulation of Hap4, the regulatory subunit of the Hap2/3/4/5 transcriptional factor complex. Many components of the 25-subunit Mediator complex negatively regulate HAP4 expression. Srb8 undergoes post-translational modification in response to changes of the carbon source. Gal11 and Med3 positively regulate HAP4 expression.

Rights

The University of New Orleans and its agents retain the non-exclusive license to archive and make accessible this dissertation or thesis in whole or in part in all forms of media, now or hereafter known. The author retains all other ownership rights to the copyright of the thesis or dissertation.

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