MRNA DECAPPING IN YEAST

生物过程的控制，如细胞生长和 分化，取决于细胞内的遗传物质是如何 表达和调节。尽管最近的许多观察强调， mRNA周转在转录后基因调控中的重要性， 对mRNA周转机制的组成部分知之甚少， 它们的活性如何被调节以产生广泛的mRNA 衰变率我们已经描述了酵母中mRNA衰变的途径， 许多（如果不是大多数）转录物，其中poly（A）尾缩短触发 在帽结构处或附近发生核裂解（脱帽）， 至转录物的5'至3'核酸外切降解。开盖是一种 这是该机制中的关键步骤，因为它是诱导降解的步骤 它是许多控制输入的位点。比如说， poly（A）尾对mRNA衰变的主要作用是通过 抑制开盖。此外，调节细胞凋亡的特定序列 mRNA衰减速率可以通过影响脱帽速率来实现。此外，委员会认为， 一种专门的降解异常转录本的衰变途径， 不依赖于poly（A）尾而触发极其快速的mRNA去帽 缩短。考虑到这一重要性，在这项资助中，我们专注于了解 开盖的机理和控制。我们将结合使用 基因和生物化学的方法来识别和确定功能 催化和控制去帽反应的基因产物。 这种分析应该提供对mRNA的一般原理的洞察力， 周转，无论是在酵母和更复杂的真核生物。具体 实验目的如下： I.为了鉴定mRNA脱帽（称为MRT）所需的基因突变 基因）。 二.为了研究MRT基因产物的功能和相互作用， vivo. 三.分析mRNA体外脱帽。

The control of biological processes, such as cellular growth and differentiation, is dependent on how the genetic material within a cell is expressed and regulated. Despite many recent observations that emphasize the importance of mRNA turnover in posttranscriptional gene regulation, little is known about the components of the mRNA turnover machinery and how their activity is modulated to give rise to the broad range of mRNA decay rates. We have described a pathway of mRNA decay in yeast shared by many, if not most, transcripts, in which poly(A) tail shortening triggers a nucleolytic cleavage at, or near, the cap structure (decapping), leading to 5' to 3' exonucleolytic degradation of the transcript. Decapping is a key step in this mechanism because it is the step that induces degradation of the mRNA, and it is the site of numerous control inputs. For example, the major effect of the poly(A) tail on mRNA decay is through an inhibition of decapping. In addition, specific sequences that modulate mRNA decay rate can do so by affecting the rates of decapping. Moreover, a specialized decay pathway that degrades aberrant transcripts works by triggering extremely rapid mRNA decapping independent of poly(A) tail shortening. Given this importance, in this grant we focus on understanding the mechanism and control of decapping. We will use a combination of genetic and biochemical approaches to identify and determine the function of the gene products that catalyze and control the decapping reaction. This analysis should provide insight into the general principles of mRNA turnover, both in yeast and in more complex eukaryotes. The specific experimental aims are as follows: I. To identify mutations in genes required for mRNA decapping (termed MRT genes). II. To examine the functions and interactions of the MRT gene products in vivo. III. To analyze mRNA decapping in vitro.