Control of Transcriptional Attenuation of Stress-induced Genes in Yeast

描述（由申请人提供）：细胞存活取决于对来自细胞外环境的应激信号作出反应的能力。不同的应激信号诱导特定基因的表达，这些基因在对应激的生理反应中起作用。在没有压力的情况下，这些基因中的许多基因的表达维持在最低水平。我们在酵母中发现了S。酿酒酵母，一个模型真核系统，许多应力诱导的基因的基础表达是最小化的一种新的机制-过早的转录终止，或转录衰减。细胞壁应激诱导的基因需要MAP激酶Mpk 1在转录过程中进行两个独立的步骤，这两个步骤都不需要其蛋白激酶活性。第一种是将转录因子募集到靶基因的启动子上。第二个涉及阻断衰减，其在非诱导条件下发生在靶基因的启动子近端区域内。衰减是由Sen 1终止复合物介导的，并通过Mpk 1易位到延伸RNA聚合酶（Pol II）来阻断。在诱导条件下，基因表达取决于衰减的缓解。对于Mpk 1诱导的基因，这是通过Mpk 1与延伸因子Paf 1的结合而发生的，Paf 1阻断了Sen 1复合物向Pol II的募集。这种相互作用在Mpk 1、ERK 5的人类直系同源物中是保守的，这表明受调控的转录衰减在人类中起作用。基于我们的初步研究结果，我们提出，各种各样的压力诱导的基因沉默的转录衰减在非诱导条件下，一个星座的转录因子可能会减轻衰减诱导条件下通过与Paf 1C（一个复杂的含有Paf 1）的相互作用。该项目的长期目标是提供一种新的方法，通过抑制转录衰减的缓解来阻断特定基因或基因组的表达。我们建议阐明调节转录衰减的机制，以及各种压力使用相似或不同的衰减缓解因子来调节各种靶基因的程度。一个直接的目标将是确定是否其他MAP激酶，响应不同的信号也作为衰减救济因素。另一个项目将确定非MAP激酶减毒-缓解因子，这些因子可以诱导我们发现在减毒控制下的各种应激诱导基因。第三个目标是了解Paf 1C在Sen 1终止复合物向Pol II募集中的作用。总的来说，这些研究将产生一个机制的理解调节转录衰减，并揭示了无处不在的过程中酵母，这将为后续的研究人类细胞。

DESCRIPTION (provided by applicant): Cell survival depends on the ability to respond to stress signals from the extracellular environment. Diverse stress signals induce the expression of specific genes that function in the physiologic response to the stress. In the absence of stress, expression of many of these genes is maintained at a minimal level. We have found in the yeast S. cerevisiae, a model eukaryotic system, that the basal expression of many stress-induced genes is minimized by a novel mechanism - premature transcriptional termination, or transcriptional attenuation. Genes induced by cell wall stress require the MAP kinase Mpk1 to carry out two separate steps in the transcription process, neither of which requires its protein kinase activity. The first is to recruit a transcription factor to promoters of target genes. The second involves blocking attenuation, which occurs within the promoter-proximal region of target genes under non-inducing conditions. Attenuation is mediated by the Sen1 termination complex and is blocked by the translocation of Mpk1 to the elongating RNA polymerase (Pol II). Under inducing conditions, gene expression depends upon the relief of attenuation. For Mpk1-induced genes, this happens through the association of Mpk1 with the elongation factor Paf1, which blocks the recruitment of the Sen1 complex to Pol II. This interaction is conserved in the human ortholog of Mpk1, ERK5, suggesting that regulated transcriptional attenuation operates in humans. Based on our preliminary findings, we propose that a wide variety of stress-induced genes are silenced by transcriptional attenuation under non-inducing conditions and that a constellation of transcription factors are likely to relieve attenuation under inducing conditions through interactions with the Paf1C (a complex containing Paf1). The long-term objective of this project is to provide a novel approach to blocking the expression of specific genes, or groups of genes, by inhibiting relief of transcriptional attenuation. We propose to elucidate the mechanisms that regulate transcriptional attenuation and the degree to which various stresses use similar or different attenuation-relief factors to regulate a variety of target genes. One immediate goal will be to determine if other MAP kinases that respond to different signals also function as attenuation-relief factors. Another project will identify non-MAP kinase attenuation- relief factors that allow the induction of a variety of stress-induced genes we have found to be under attenuation control. A third goal will be to understand the role of the Paf1C in the recruitment of the Sen1 termination complex to Pol II. Overall, these studies will yield a mechanistic understanding of regulated transcriptional attenuation and reveal the ubiquity of the process in yeast, which will inform subsequent studies on human cells.