Mating Type Silencing and Switching in Yeast

描述（由申请人提供）：我们建议在三个不同但相互关联的领域调查酵母的交配类型。首先，我们计划探索异染色质沉积和维持的机制，使用一种新的视觉检测方法，在交配型位点沉默，以确定活跃状态和抑制状态之间的相互转换动力学，并评估影响这些转换速率的因素。这些结果应该阐明影响诸如x失活和染色体印记等多种事件的调控过程，这些事件是各种疾病（如散发性癌症）的基础。其次，交配型相互转换过程中的供体选择需要在酵母基因组的遥远区域之间进行发育调节的选择性相互作用。我们计划通过在选择过程中完成基于基因组的突变体筛选，并通过检查活细胞中交配类型相互转换的动力学来探索这一过程的机制基础，以测试这一重组过程的遗传基础。这些观察结果将有助于深入了解更大的真核生物的类似发育事件，如免疫球蛋白类转换和序次Pglobin激活。最后，酵母细胞通过启动转录和发育程序来响应信息素，最终导致交配。我们最近发现，种群中的单个细胞对信息素的反应有两种不同的模式：一些细胞根本没有反应，而其余的细胞则表现出完全的交配反应。这种分化的反应部分是由于不同MAP激酶信号通路之间的抑制串扰。我们建议扩展这些研究，以探索负责信息素反应和假菌丝和侵袭性生长的MAP激酶途径之间的串扰。这些研究结果将有助于揭示细胞信息处理过程中信号整合的机制。所有这些研究，虽然探索酵母细胞类型和交配反应的不同方面，但通过检查单个细胞和从其独特的个体行为中提取生物学和机制原理的共同技术和理论方法，将它们统一起来。

DESCRIPTION (provided by applicant): We propose to investigate mating type in yeast in three distinct but interrelated areas. First, we plan to explore the mechanism by which heterochromatin is deposited and maintained using a novel visual assay for silencing at the mating type loci to determine the dynamics of interconversion between the active and repressed states and to assess the factors that influences those rates of conversion. These results should shed light on the regulatory processes affecting such diverse events as X-inactivation and chromosome imprinting, which underlies various diseases such as sporadic cancers. Second, donor selection during mating type interconversion requires developmentally-regulated, selective interaction between distant regions of the yeast genome. We plan to explore the mechanistic basis of this process by completing a genome-based screen for mutants altered in the selection process and by examining the dynamics of mating type interconversion in living cells to test the genetic underpinnings of this recombination process. These observations should yield insights into similar developmental events in larger eukaryotes, such as immunoglobulin class switching and sequential Pglobin activation. Finally, yeast cells respond to pheromone by initiating a transcriptional and developmental program culminating in mating. We recently found that individual cells within the population respond to pheromone in one of two distinct patterns: some cells show no response at all while the remaining cells exhibiting a full mating response. This bifurcated response is due in part to inhibitory cross talk among different MAP kinase signaling pathways. We propose to extend these studies to explore the crosstalk between the MAP kinase pathways responsible for pheromone response and for pseudohyphal and invasive growth. The results of these studies should shed light on the mechanism for signal integration in information processing in cells. All these studies, while probing different aspects of cell type and mating response in yeast, are unified by the common technical and theoretical approaches of examining individual cells and extracting biological and mechanistic principles from their distinct individual behaviors.