Cell Cycle regulation of the yeast HO Gene

描述（由申请人提供）：控制细胞周期的机制在所有真核生物中非常保守。在大多数生物体中，进行一轮细胞分裂的决定发生在G1期，致癌过程通过干扰G1期进展的调节因子发挥其最大的影响。我们的研究集中在控制生长和静止细胞进入有丝分裂细胞周期的决定的分子机制。细胞周期蛋白依赖性激酶（Cdks）控制G1到S的转变。在芽殖酵母中，有三个G1细胞周期蛋白在两个连续的波中转录调节。第一波转录产生Cln 3细胞周期蛋白和转录因子Swi 4。在G1早期，Cln 3激活细胞周期蛋白依赖性激酶（Cdk），这反过来又激活Iate-G1转录复合物Swi 6/Swi 4和Swi 6/Mbp 1。这些复合物调节超过200种转录物，包括细胞周期蛋白产生的晚期G1波，这是向S期过渡的关键。现在比以往任何时候，晚G1转录的机制类似于后生动物途径，因为视网膜母细胞瘤（Rb）的酵母等效物已被确定。这种蛋白质Whi 5抑制晚期G1转录，并且可以通过Cln 3/Cdk磷酸化被磷酸化并从转录复合物中释放。我们建议建立晚G1转录复合物组件和Whi 5之间的关系，并确定这些组件的活动是如何影响的信号通路，影响启动响应内在和外在的线索。这在快速生长的细胞中很重要，但同样重要的是要了解启动程序的修改，使细胞能够进入，维持和从静止状态恢复，因为这是实验室外更普遍的过渡。大多数细胞从G1退出周期。要做到这一点，有丝分裂启动机制必须稳定失活，然后在条件改善时重新激活。我们第一次能够纯化出从GO同步进入S期的GO细胞的均匀群体。我们将使用这种方法来测试一系列解除有丝分裂起始程序的突变体，以了解GO到S和G1到S的差异。

DESCRIPTION (provided by applicant): The mechanisms that control the cell cycle are remarkably conserved among all eukaryotes. The decision to commit to a round of cell division occurs in G1 in most organisms and oncogenic processes exert their greatest impact by interfering with regulators of G1 progression. Our research is focused on the molecular mechanisms that control the decision to enter the mitotic cell cycle in growing and quiescent cells. The control of the G1 to S transition is governed by cyclin-dependent kinases (Cdks). In budding yeast, there are three G1 cyclins that are transcriptionally regulated in two consecutive waves. The first wave of transcription produces components the Cln3 cyclin and the transcription factor Swi4. During early G1, Cln3 activates the cyclin-dependent kinase (Cdk), which, in turn activates the Iate-G1 transcription complexes, Swi6/Swi4 and Swi6/Mbp1. These complexes regulate over 200 transcripts, including the late G1 wave of cyclin production, which is key to the transition to S phase. Now more than ever, the mechanism of late G1 transcription resembles the metazoan pathway, in that the yeast equivalent of Retinoblastoma (Rb) has been identified. This protein, Whi5, represses late G1 transcription and can be phosphorylated and released from the transcription complex by Cln3/Cdk phosphorylation. We propose to establish the relationships between the late G1 transcription complex components and Whi5 and to identify how the activities of these components are affected by the signaling pathways that influence Start in response to intrinsic and extrinsic cues. This is important in rapidly growing cells, but it is equally important to understand the modifications of the Start program that enable cells to enter, maintain and recover from quiescence, because this is the more prevalent transition outside the laboratory. Most cells exit the cycle from G1. To do so, the mitotic Start machinery must be stably inactivated and then reactivated when conditions improve. For the first time, we are able to purify a uniform population of GO cells that synchronously enter S phase from GO. We will use this method to test a series of mutants that deregulate the mitotic start program to see how GO to S and G1 to S differ.