Control of the cell cycle by mRNA degradation.

描述（由申请人提供）：近年来，在酵母和哺乳动物中，调节蛋白水解复杂地参与控制细胞周期，这一发现引起了极大的兴奋。我们发现，调节核糖核酸酶的消化在酵母细胞周期的控制中也起着至关重要的作用。本研究的主要目的是确定核糖核蛋白核糖核酸内切酶RNase MRP在细胞分裂周期晚期破坏mRNA稳定的位点、机制和调控。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细胞周期晚期阻滞的特征，细胞不能分解纺锤体或进行细胞质分裂。这种从M到G1的阻滞通常由CDC5、DBF2组突变定义。这些从M到G1的突变体导致无法关闭Clb1&2/Cdc28细胞周期蛋白/激酶。该激酶的失活是纺锤体解体、细胞分裂和进入G1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由于不能快速降解CLB2 mRNA的结果。CLB2 mRNA的增加导致CIb2蛋白、相关激酶活性和细胞周期阻滞的增加。项目期间的具体目标将包括表征CLB2 mRNA降解途径，确定RNase MRP除CLB2 mRNA外的直接靶点。基因组技术将用于鉴定细胞中所有潜在的RNase MRP底物。一系列的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在细胞周期中的调控，并确定这种调控的手段。RNase MRP在M到G1转变中的作用的重要性不能被夸大。特定mrna的调节降解可能在细胞周期控制中发挥与调节蛋白水解同样重要的作用。许多这些晚期作用基因具有人类同源物（PTEN/MMAC1, PIk, Polo, p55CDC），它们密切参与调节细胞周期和细胞增殖。人类也有类似酵母酶的RNA和蛋白质亚基的RNase MRP复合体。人类RNase MRP的突变导致软骨毛发育不全。这种疾病的表现是由一般的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.