REGULATION OF YEAST PHO5 GENE

这项工作的长期目标是了解细胞如何感知和响应细胞外信号。我们将研究芽殖酵母中一个重要的信号转导级联反应胞外无机磷水平的变化(Pho途径)。我们先前已经证明，转录因子Pho4是磷酸反应信号转导通路的靶点，该通路由Pho80-Pho85细胞周期蛋白依赖性激酶(CDK)复合体和CDK抑制剂Pho81组成。我们对这些成分的功能和调节了解很多，但对细胞如何感知磷酸盐水平并产生适当的生理反应知之甚少。我们将重点研究Pho通路如何处理信息并协调对不同磷酸盐水平的反应。除了参与磷酸盐代谢的细胞周期蛋白Pho80外，CDK Pho85还与9个周期蛋白联系在一起。这些Pho85-Cyclin复合体调控的过程尚不清楚，很大程度上是因为几乎没有发现与生理相关的底物。我们将采用一种新的方法来鉴定蛋白激酶底物，目的是深入了解CDK Pho85调控的生物过程。最终，磷酸信号到达细胞核，导致对磷酸反应基因的调控，如PH05。PH05基因启动子是研究基因调控与染色质结构关系的一个很好的系统。我们最近已经确定了重塑PH05启动子染色质所需的因素，并观察到小分子(肌醇多聚磷酸盐)调节这一过程。我们将重点了解染色质是如何在PH05启动子上重塑的，以及这个过程是如何调控的。这些研究将深入了解信号转导和转录调控的机制，以及在人类疾病和癌症中被错误调控的基本细胞生物学过程。

The long-term goal of this work is to understand how cells sense and respond to extracellular signals. We will study a signal transduction cascade in budding yeast important for responding to changes in the level of extracellular inorganic phosphate (the "Pho" pathway). We have previously shown that the transcription factor Pho4 is a target for a phosphate-responsive signal transduction pathway composed of the Pho80-Pho85 cyclin-cyclin dependent kinase (CDK) complex and the CDK inhibitor Pho81. We understand much about the function and regulation of these components, but little about how cells sense phosphate levels and generate an appropriate physiological response. We will focus on how the Pho pathway processes information and coordinates a response to different phosphate levels. The CDK Pho85 associates with nine cyclins, in addition to the cyclin Pho80 involved in phosphate metabolism. The processes regulated by these Pho85-cyclin complexes are unclear, largely because few physiologically-relevant substrates have been identified. We will employ a new method for identification of protein kinase substrates, with the goal of providing insight into the biological processes regulated by the CDK Pho85. Ultimately the phosphate signal reaches the nucleus, resulting in regulation of phosphate-responsive genes such as PH05. The promoter of the PH05 gene is an excellent system for studying the relationship between gene regulation and chromatin structure. We have recently identified factors which are required to remodel PH05 promoter chromatin and have observed that small molecules (inositol polyphosphates) regulate this process. We will focus on understanding how chromatin is remodeled at the PH05 promoter and how this process is regulated. These studies will provide insight into mechanisms of signal transduction and transcriptional regulation, basic cell biological processes which are misregulated in human diseases and cancer.