Regulation of G1-specific gene expression in yeast

描述（由申请人提供）：忠实复制的能力是生命系统的标志之一。我们研究计划的总体目标是了解真核生物细胞增殖的控制。这种调控是在细胞周期的G1期通过调控一个大家族G1特异性基因的表达而施加的。我们之前已经描述了酵母中g1特异性基因表达的两种新的抑制因子。在G1期早期，wh5结合并抑制两种G1特异性转录因子之一SBF，而Nrm1与MBF共同抑制G1特异性转录，在细胞退出G1期时抑制G1特异性转录。这两种调节因子在细胞周期检查点中发挥关键作用，对细胞周期事件施加秩序：wh5在G1细胞大小检查点中，Nrm1在DNA复制检查点中。该应用程序有三个具体目的。首先，我们提出通过研究sw6与wh5和Nrm1相互作用的基础，以及通过蛋白磷酸化对这种相互作用的调节，来表征sw6作为MBF和SBF的共同成分作为转录调节平台的作用。其次，我们建议通过DNA复制检查点确定MBF调控转录的机制和作用。Nrm1在检查点信号通路和细胞周期机制之间起联系作用。检查点通过检查点蛋白激酶的磷酸化调节Nrm1/MBF相互作用，对基因组稳定性很重要。第三，我们建议建立RAK基序的作用，RAK基序保守于Nrm1， wh5和其他定义Nrm1/ wh5超家族的蛋白质之间。我们期望这种氨基酸序列的保守性掩盖了这些蛋白质对细胞周期调节的保守性。我们预计，这些特定目标的完成将提供更广泛的理解g1特异性转录调控在细胞周期和响应的激活

DESCRIPTION (provided by applicant): The capacity to faithfully replicate is one of the hallmarks of living systems. The overall goal of our research program is to understand the control of cell proliferation in eukaryotes. That regulation is imposed during G1 phase of the cell cycle via the regulation of the expression of a large family of G1- specific genes. We have previously described two novel repressors of G1-specific gene expression in yeast. Whi5 binds and represses SBF, one of two G1-specific transcription factors, during early G1 phase whereas Nrm1 acts as a co-repressor with MBF to repress G1 specific transcription as cells exit G1 phase. Both regulators play critical roles in cell cycle checkpoints that impose order on cell cycle events: Whi5 in the G1 cell size checkpoint and Nrm1 in the DNA replication checkpoint. The application is presented in three specific aims. First, we propose to characterize the role of Swi6, a shared component of MBF and SBF, as a platform for regulation of transcription by studying the basis for its interaction with Whi5 and Nrm1 and the regulation of that interaction by protein phosphorylation. Second, we propose to determine the mechanism and role of control of MBF regulated transcription by the DNA replication checkpoint. Nrm1 acts at the nexus between the checkpoint signaling pathway and the cell cycle machinery. The checkpoint regulates the Nrm1/MBF interaction via phosphorylation by checkpoint protein kinases and is important for genomic stability. Third, we propose to establish the role of the RAK motif, an amino acid sequence motif conserved between Nrm1, Whi5 and other proteins that defines a Nrm1/Whi5 superfamily. We expect that this amino acid sequence conservation belies a conserved aspect of cell cycle regulation by those proteins. We anticipate that completion of these specific aims will provide a broader understanding of the regulation of G1-specific transcription both during the cell cycle and in response to activation of the DNA replication checkpoint. Understanding this mechanism in the distantly related budding yeast, Saccharomyces cerevisiae, and fission yeast, Schizosaccharomyces pombe, promises to establish paradigms to be tested in the context of the regulation of cell proliferation and the human DNA replication checkpoint response. Misregulation of both of those processes has been associated with human cancer. We are hopeful that a more general view of the cell cycle-regulated transcriptional machinery and its regulators will offer insight into human biology and medicine.