GENETIC REGULATION OF YEAST CELL TYPE

该提案研究了细胞特化的分子基础， 在酵母Saccharomyces cerevisiae中的细胞间通讯 在 在其生命周期的过程中，酵母表现出三种不同的细胞 表型 其中两种细胞类型，a和alpha，专门用于 交配 它们通过产生细胞类型特异性的 蛋白质，例如信息素和信息素受体， 他们互相示意，准备交配。 这里提出的工作有两个广泛的目标。 首先，我们要 了解细胞特化的分子基础。 差动 产生α和α细胞类型的基因表达由以下因素控制： 调节蛋白，α 1和α 2，由α交配型编码 基因座 这些蛋白质与一种普通的转录 因子MCM1，以控制α-特异性和α-特异性 基因. MCM1的一个非常小的片段足以执行所有的操作。 已知的功能。 我们将对这部分进行诱变， 与共调节因子相互作用以及 转录激活 此外，我们还将确定 与MCM1富含谷氨酰胺的片段相互作用，该片段也能够 导致转录激活。 第二个目标是了解对信息素的反应途径。 信息素与其同源受体的结合激活了一种信号 在应答中引起生理变化的转导途径 cell. 这些变化包括通过有丝分裂的进展停滞， 细胞周期和基因转录的增加， 催化交配 尽管反应途径中的几个步骤 已确定，各组成部分之间的关系，以及它们如何 活动是否受到管制尚不清楚。 我们将进行系统的 寻找表现出组成型活性反应途径的突变体。 我们还将通过分离突变体来鉴定新的途径组分， 不能执行信息素反应的特定方面。 比如说， 我们将选择不能经历细胞周期停滞但 转录诱导正常。 我们将订购 通过双突变体分析，使用本研究中鉴定的突变体 项目以及现有的突变体。 我们将确定活动如何 蛋白激酶STE11是一种特定的途径成分， 监管. 这一努力将由主导的属性， 组成型STE11等位基因是我们最近分离的。 最后我们将 识别在受体处起作用以减弱 信息素产生的信号，因此允许有丝分裂生长恢复。

This proposal examines the molecular basis of cell specialization and cell-cell communication in the yeast Saccharomyces cerevisiae. In the course of its life cycle yeast exhibits three distinct cellular phenotypes. Two of the cell types, a and alpha, are specialized for mating. They are distinguished by the production of cell-type-specific proteins, for example pheromones and pheromone receptors, that enable them to signal their presence to one another and prepare for mating. There are two broad goals for the work proposed here. First, we want to understand the molecular basis for cell specialization. The differential gene expression that generates the a and alpha cell types is governed by regulatory proteins, alpha1 and alpha2, encoded by the alpha mating-type locus. These proteins work in combination with a general transcription factor, MCM1, to control transcription of alpha-specific and a-specific genes. A remarkably small segment of MCM1 is sufficient to carry out all its known functions. We will mutagenize this segment to identify residues that are required for interaction with co-regulators and for transcription activation. In addition, we will identify functions that interact with a glutamine-rich segment of MCM1 that is also capable of bringing about transcription activation. The second goal is to understand the pathway of response to pheromone. Binding of pheromone to its cognate receptor activates a signal transduction pathway that elicits physiological changes in the responding cell. These changes include arrest of progression through the mitotic cell cycle and an increase in the transcription of genes whose products catalyze mating. Although several steps in the response pathway have been identified, the relationships among the components and how their activities are regulated is not known. We will carry out a systematic search for mutants that exhibit a constitutively active response pathway. We will also identify new pathway components by isolating mutants that cannot carry out particular aspects of pheromone response. For example, we will select for mutants that cannot undergo cell cycle arrest but are normal for transcription induction. We will order components of the pathway by double mutant analysis, using mutants identified in this project as well as existing mutants. We will determine how the activity of a particular pathway component, the protein kinase STE11, is regulated. This effort will be guided by the properties of dominant, constitutive STE11 alleles recently isolated by us. Finally, we will identify functions that operate at the receptor to attenuate the pheromone-generated signal and therefore allow mitotic growth to resume.