Control of the cell cycle by mRNA degradation.

描述（由申请人提供）：近年来，大量令人兴奋的发现围绕着受调节的蛋白水解复杂地参与控制酵母和哺乳动物的细胞周期。我们已经发现，受调节的核糖核酸酶消化在控制酵母细胞周期中也起着至关重要的作用。该建议的主要目的是确定在细胞分裂周期末期由核糖核蛋白内切核糖核酸酶RNase MRP引起的mRNA不稳定的位点、机制和调节。我们已经发现，RNase MRP酶复合物的不同组分的突变导致细胞分裂周期（CDC）停滞。分裂的细胞核和细长的纺锤体是这种晚期细胞周期停滞的特征，在这种细胞周期停滞中，细胞无法分解其纺锤体或进行胞质分裂。这种从M到G1的停滞通常由CDC 5、DBF 2突变组定义。这些M到G1突变体导致不能关闭Clb1&2/Cdc 28细胞周期蛋白/激酶。激酶的失活是纺锤体解体、胞质分裂和进入G1期的能力所必需的。结果表明，RNase MRP突变体的细胞分裂周期停滞是未能快速降解CLB 2 mRNA的结果。CLB 2 mRNA的增加导致Cib 2蛋白、相关激酶活性和细胞周期停滞的增加。项目期间的具体目标将包括表征CLB 2 mRNA降解的途径，并确定除CLB 2 mRNA外的RNase MRP的直接靶点。基因组技术将用于鉴定细胞中所有潜在的RNase MRP底物。一系列生化和遗传分析将确定不稳定因素和RNase MRP作用的直接位点。最后，我们将研究RNase MRP在细胞周期中的调节，并确定该调节的方法。RNase MRP在M到G1过渡中的作用的重要性不能被夸大。特定mRNA的调节降解在细胞周期控制中可能与调节蛋白水解一样重要。这些迟发作用基因中的许多具有与调节细胞周期和细胞增殖密切相关的人类同源物（PTEN/MMAC 1、PIk、波罗、p55 CDC）。人类也有一个RNase MRP复合体，其RNA和蛋白质亚基类似于酵母酶。人核糖核酸酶MRP的突变导致一种多效性疾病，即软骨毛发发育不全。这种疾病的表现是由一般细胞增殖缺陷引起的，类似于我们在酵母中看到的。这将使我们能够使用一个简单的遗传模型系统来深入了解人类疾病。

DESCRIPTION (provided by applicant): In recent years a tremendous amount of excitement has surrounded the finding that regulated proteolysis is intricately involved in controlling the cell cycle in yeast and mammals. We have found that regulated ribonuclease digestion also plays a crucial part in controlling the cell cycle in yeast. The major objective for this proposal is to determine the sites, mechanism and regulation of mRNA destabilization by the ribonucleoprotein endoribonuclease RNase MRP in late telophase of the cell division cycle. We have discovered that mutations of different components of the RNase MRP enzyme complex lead to a cell division cycle (CDC) arrest. Divided nuclei and an elongated spindle characterize this late cell cycle arrest, in which cells fail to disassemble their spindle or to undergo cytokinesis. This M to G1 arrest is classically defined by the CDC5, DBF2 group of mutations. These M to G1 mutants lead to the inability to turn off the Clb1&2/Cdc28 cyclin/kinase. Inactivation of the kinase is required for disassembly of the spindle, cytokinesis and the ability to enter G1. Results indicate that the cell division cycle arrest in RNase MRP mutants is the result of a failure to rapidly degrade the CLB2 mRNA. Increased CLB2 mRNA leads to increased CIb2 protein, associated kinase activity and cell cycle arrest. The specific goals during the project period will include characterizing the pathway of CLB2 mRNA degradation and determining direct targets of RNase MRP in addition to CLB2 mRNA. Genome technology will be used to identify all of the potential RNase MRP substrates in a cell. A series of biochemical and genetic analyses will identify instability elements and the direct sites of RNase MRP action. Lastly, we will investigate the regulation of RNase MRP during the cell cycle and determine the means of that regulation. The significance of the role of RNase MRP in the M to G1 transition cannot be overstated. Regulated degradation of specific mRNAs may play as large a part in cell cycle control as regulated proteolysis. Many of these late acting genes have human homologues (PTEN/MMAC1, PIk, Polo, p55CDC) that are intimately involved in regulating the cell cycle and cell proliferation. Humans also have an RNase MRP complex with RNA and protein subunits similar to the yeast enzyme. Mutations in human RNase MRP cause a pleotropic disease, Cartilage Hair Hypoplasia. The manifestations of this disease are caused by a general cell proliferation defect, similar to what we see in yeast. This will allow us to use a simple genetic model system to lend insights into human disease.