Dr. Robert Ramirez
Role of histone deacetylases in mitotic recombination.
We are interested in the function of RPD3 gene of yeast and its role in mitotic recombination. We originally identified REC3 as a temperature sensitive mutation which decreased the rate of spontaneous mitotic recombination. Other investigators have shown that RPD3 encodes a histone deacetylase which modifies chromatin structure. Additional studies in our laboratory show that RPD3 and REC3 are the same gene. and mutation in this gene affect sporulation and induce aberrant acid phosphatase expression. In addition, RPD3 is one of five homologous genes in yeast that encode enzymes called histone deacetylases which are involved in the modification of chromatin structure. This finding is significant because it suggests a relationship between chromatin structure, gene expression and mitotic recombination. We are currently involved in the examination of the roles played by the remaining four RPD3-homologs (HOS1, HOS2, HOS3, HDA1) in mitotic recombination, sporulation, gene expression or DNA repair.

Genetics and physiology of osmotic stress in the yeast Saccharomyces cerevisiae.
We are currently using biochemical assays and HPLC to analyze the intracellular osmolyte content of yeast cells subjected to hyperosmotic stress. These studies have shown that yeast cells respond to osmotic stress by low-level accumulation of methylamine osmolytes (choline, glycerophosphorylcholine, glycine betaine) while glycerol accumulates ten-fold. Future studies will examine the role played by endogenous choline biosynthesis on the ability of cells to tolerate osmotic stress. We will examine the osmotic phenotype of opi3 mutants (that cannot synthesize choline) and hmn1 mutant (which cannot transport choline) in order to identify additional genetic factors which correlate with osmotic sensitivity.




Last modified July 10, 2002