Silenced Chromatin: Mechanisms of Transcriptional Repression

这个项目将使用模式生物，面包酵母，研究染色体结构，“沉默”（关闭）基因表达和分子事件，伴随着这种沉默的基因随后被激活（打开）的过程。酵母基因与复杂生物有许多共同的特征，包括“串珠”结构和重要的调控机制。在正确的时间和正确的地点关闭特定的基因（即，在适当的组织内）对正常发育、健康和生存至关重要。因此，了解基因表达如何沉默（抑制）的分子细节非常有趣，尤其是最近的证据表明，这种情况在酵母、昆虫和人类中发生的方式非常相似。该项目的目标是：（1）证明RNA聚合酶（负责将DNA复制成信使RNA的酶）存在，但由于沉默基因中独特的染色体结构而无法工作;（2）表征当沉默的基因响应于环境刺激而被激活时发生的分子变化，并将这些改变与那些能够表达更高水平的非沉默基因中所见的改变进行比较;和（3）鉴定在激活过程中帮助RNA聚合酶克服沉默基因结构的抑制作用的蛋白质，并将这些蛋白质与非沉默基因结构所用的蛋白质库进行比较。沉默的基因该项目还将为博士后、研究生和本科生提供培训。

This project will use the model organism, baker's yeast, to investigate both the chromosomal structures that 'silence' (shut down) gene expression and the molecular events that accompany the process by which such silenced genes are subsequently activated (turned on). Yeast genes share many features in common with those of complex organisms, including a 'beads-on-a-string' structure and important regulatory mechanisms. Shutting off specific genes at the right time and in the right place (i.e., within the proper tissue) is critical for normal development, health and survival. Understanding the molecular details of how gene expression is silenced (repressed) is therefore of great interest, all the more so given recent evidence suggesting that the way this happens is remarkably similar in yeast, insects and humans. The goals of this project are: (1) to demonstrate that RNA polymerase, the enzyme responsible for copying the DNA into messenger RNA, is present but rendered incapable of working by the specialized chromosomal structures uniquely seen in silenced genes; (2) to characterize the molecular changes that occur when silenced genes become activated in response to an environmental stimulus, and to compare these alterations with those seen in non-silenced genes that are capable of far higher levels of expression; and (3) to identify the proteins that assist RNA polymerase in overcoming the repressive effects of silenced gene structure during activation and compare these to the repertoire of proteins employed for non-silenced genes. The project will also provide training to post-doctoral, graduate, and undergraduate students.