Title

Transcriptional Activation by Rap1p, Gcr1p and Gcr2p In the Yeast Saccharomyces cerevisiae

Author

Xiao Zeng

Date of Award

1997

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

First Advisor

George Santangelo

Advisor Department

Biological Sciences

Abstract

In the yeast Saccharomyces cerevisiae, efficient expression of most glycolytic genes requires three transcription factors: Rap1p, Gcr1p and Gcr2p. In this study, I have demonstrated a functional relationship among these factors which leads to a model that explains the different requirements in UAS$\sb{\rm rpg}$-dependent (Rap1p-bound) promoters with respect to their requirement for the three factors. Since I was able to co-immunoprecipitate Gcr1p and Rap1p in vitro, we proposed that Gcr1p and Rap1p form a complex in vivo, a working model that is now well supported by other genetic and biochemical evidence. I have demonstrated that Gcr2p's role in the cell is to mediate the CT box effect; I have also shown evidence suggesting that this specialized function of the Rap1p/Gcr1p complex may be regulated by a conformational change in Gcr1p. By further investigation along these lines, I have discovered that Gcr1p is phosphorylated primarily in a region that is dispensable for Gcr1p function. However, mutant alleles with this region deleted can now bypass the requirement for Gcr2p. Furthermore, I present evidence suggesting that phosphorylation of Gcr1p may regulate its stability and that Gcr2p is required for the hyper-phosphorylation of Gcr1p. Further implications of the transcriptional activation by Rap1p/Gcr1p/Gcr2p are discussed.