Elongation and termination of transcripts by RNA pol II

描述（由申请人提供）：RNA聚合酶II在转录水平上对基因表达的控制是健康细胞生命的核心，并且在疾病中经常被破坏。在转录周期的每个阶段，起始、延伸和终止，聚合酶必须与DNA模板协商，DNA模板与组蛋白一起包装成染色质。转录机器对DNA的访问在一个水平上通过修饰其尾部的组蛋白来调节。我们最近在酵母和哺乳动物中发现了一类新的酶， 通过去除组蛋白H3上赖氨酸4处的甲基，对组蛋白尾部进行修饰（附录3）。这类新的脱甲基酶属于一个名为JARID 1的家族，其中一个成员在酵母中，四个成员在哺乳动物中。它们几乎可以肯定是针对单个基因来调节它们的表达，但我们仍然不知道它们针对的是哪些基因。在芽殖酵母中，我们发现，当JARID1同源物（Yjr119c）突变时，孢子形成（基因表达中高度调节变化的主要程序）被严重破坏。酵母中的孢子形成是高等生物发育过程中调控基因活性的一个很好的模型。通过研究何时以及如何破坏孢子形成程序，我们的目标是揭示H3K4去甲基化有助于在复杂的发育程序中正确控制基因活性的机制。在延伸过程中，pol II面临着在染色质中穿行的挑战。pol II如何与染色质相互作用是一个主要的开放问题。我们发现，在酵母中，H3K4甲基化的快速变化发生在对转录延伸的急性抑制（“转录应激”）的反应中（附录1），并正在研究这种机制是否在多细胞动物中保守。也许pol II转录周期中最不为人所知的部分是终止，通过这个过程，pol II被告知它已经到达基因的末端，然后从DNA模板中释放出来。我们提出了一个新的终止如何触发的模型（附录2），并将研究如何在转录周期的最后一步是由RNA聚合酶II和相关的终止因子的属性控制。

DESCRIPTION (provided by applicant): The control of gene expression at the level of transcription by RNA polymerase II is central to the life of the healthy cell and is frequently corrupted in disease. During each stage of the transcription cycle, initiation, elongation and termination, the polymerase must negotiate with a DNA template that is packaged with histones into chromatin. Access by the transcription machinery to the DNA is regulated at one level through modifications of the histones on their tails. We recently identified a new class of enzymes in yeast and mammals that modify the histone tails by removing methyl groups at Lysine 4 on histone H3 (Appendix 3). This new class of demethylase enzymes belong to a family called JARID1 with one member in yeast and four in mammals. They are almost certainly targeted to individual genes to regulate their expression but we still do not know which genes they are targeted to. In budding yeast we have found that sporulation, a major program of highly regulated changes in gene expression, is severely disrupted when the JARID1 homologue (Yjr119c) is mutated. Sporulation in yeast is an excellent model for regulated gene activity during development in higher organisms. By studying when and how the sporulation program is disrupted, we aim to uncover the mechanism by which H3K4 demethylation contributes to proper control of gene activity in a complex developmental program. During elongation, pol II faces the challenge of ploughing its way through chromatin. How elongating pol II interacts with chromatin is a major open question. We found that rapid changes in H3K4 methylation occur in yeast in response to acute inhibition of transcription elongation ("transcriptional stress") (Appendix 1) and are investigating whether this mechanism is conserved in multicellular animals. Perhaps the least well understood segment of the pol II transcription cycle is termination, the process by which pol II is informed that it has reached the end of the gene and is then released from the DNA template. We proposed a new model for how termination is triggered (Appendix 2) and will investigate how this final step in the transcription cycle is controlled by properties of RNA polymerase II and associated termination factors.