GENETIC CONTROL OF NUTRITIONAL STARVATION IN YEAST

实验旨在确定酵母倍性控制基因表达的机制。这项工作对人类异常细胞生长具有启示意义，因为具有异常细胞控制的肿瘤细胞通常包含异常数量的染色体。虽然肥大体通常被认为是细胞周期控制异常的结果，但这一建议表明，肥大体本身可能导致细胞增殖所需关键分子的异常表达。基因阵列将用于确定等基因酵母菌株的基因转录的倍性控制的分子基础，其倍性从单倍体到四倍体不等。一组实验旨在确定G1周期蛋白转录在细胞大小和细胞增殖的倍性控制中的作用。这些研究将确定倍性控制本身是否受细胞周期调节。由于多倍体细胞比它们的整倍体细胞对营养饥饿更敏感，因此将确定导致整倍体和多倍体生长控制差异的基因。将确定交配型位点杂合性和染色体配对在多倍体对营养饥饿的反应中的作用。对已知受倍性转录控制的基因之一的启动子进行分析，以确定对倍性控制有反应的顺式作用序列。另一种筛选是用来鉴定介导倍性控制的反式基因。耐盐性是一种倍性敏感表型，将用于筛选倍性依赖表型的抑制因子。此外，还将阐明盐敏感性的细胞基础。第三组实验确定了Rim1转录因子在固定期代谢中的作用。这种已知的真菌青霉素生产调节剂的酵母同源物被提议控制酵母菌的固定相代谢。第四组实验集中在双苯二胺的作用，一个保守的翻译后修饰的延伸因子2在细胞调节。DPH突变体具有固定相缺陷，在二倍体中比在单倍体中更为严重。提出的实验将导致更深入地了解倍性在异常细胞增殖中的作用。

Experiments are designed to determine the mechanism by which gene expression is controlled by ploidy in the yeast Saccharomyces cerevisiae. This work has implications for abnormal cell growth in humans because tumor cells with aberrant cell control often contain an abnormal number of chromosomes. Although hyperploidy is usually viewed as a consequence of aberrant cell cycle control, this proposal suggests that hyperploidy itself may cause the abnormal expression of key molecules required for cell proliferation. Gene arrays will be used to determine the molecular basis for the ploidy control of gene transcription in isogenic yeast strains whose ploidy varies from haploid to tetraploid. One set of experiments is designed to identify the role of G1 cyclin transcription in the ploidy control of cell size and cell proliferation. These studies will determine whether ploidy control is itself cell cycle regulated. As polyploid cells are much more sensitive to nutritional starvation that their euploid counterparts, the genes responsible for the differences in euploid and polyploid growth control will be identified. The role of heterozygosity at the mating type locus and chromosome pairing in the response of polyploids to nutritional starvation will be ascertained. The promoter of one of the genes known to be transcriptionally controlled by ploidy will be analyzed to identify cis-acting sequences that respond to ploidy control. Another screen is designed to identify the trans-acting genes that mediate ploidy control. Salt resistance, a ploidy sensitive phenotype, will be used to screen for suppressors of the ploidy dependent phenotype. In addition the cellular basis for salt sensitivity will be elucidated. A third set of experiments identifies the role of the Rim1 transcription factor in stationary phase metabolism. This yeast homolog of a known fungal regulator of penicillin production is proposed to control stationary phase metabolism in Saccharomyces. A fourth set of experiments focuses on the role of dipthamide, a conserved posttranslational modification of elongation factor2 in cellular regulation. dph mutants have a stationary phase defect that is again more severe in diploids that in haploids. The experiments proposed will lead to a deeper understanding of the role of ploidy in aberrant cell proliferation.