CHARACTERIZATION OF THE S POMBE CAMP SIGNAL PATHWAY

响应环境信号的转录调控包括

Transcriptional regulation in response to environmental signals involves important mechanisms employed by cells to control the processes of cell growth, differentiation and development. In unicellular organisms, changes in the carbon source available can trigger dramatic alterations in transcription of genes involved in carbon source utilization and gluconeogenesis. For example, glucose causes the repression of transcription of genes required for the utilization of other carbon sources. This phenomenon has been termed glucose repression or catabolite repression. My work focuses on glucose repression of fbp1 (encoding fructose-1,6bisphosphatase) transcription in the yeast Schizosaccharomyces pombe. S. pombe is a genetically pliable organism that resembles higher eukaryotic cells in many respects. While this organism has been widely and very successfuly exploited in the area of cell cycle control, few studies have been carried out in the area of transcriptional regulation. I have identified aset of genes, designated git genes (git=glucose insensitive transcription), required for glucose repression of fbp1 transcription, including the adenylate cyclase gene (git2). The trasncriptional defect in strains carrying a mutation in git2 or any six additional git genes is suppressed by exogenous cAMP. This suppression, along with other genetic and biochemical observations, suggests that these genes function to stimulate adenylate cyclase in response to glucose. I therefore propose to measure cAMP levels in wild type cells upon exposure to glucose, and to analyze further git2 mutants that appear to be defective in response to glucose. I also propose to carry out molecular analyses of these git genes and of nft genes (nft mutants are defective in depression of fbp1 transcription; nft= nonderepressible fbp1 transcription). I will clone the wild type copies of these genes, determine their DNA sequences, construct null alleles, and examine the null phenotypes with regard to cAMP levels and fbp1 transcription. I will also characterize spontaneous git and nft mutants by cAMP assays, genetic analyses and fbp1 transcriptional assays to identify the pathway for activation of adenylate cyclase in S. pombe.