RNA Polymerase II Elongation Complex:Structure-Function

描述（由申请人提供）： RNA聚合酶II对转录物的延伸是一个复杂的过程，依赖于核苷酸底物水平、延伸因子和共转录事件（如剪接）。编码延伸因子SII（TFIIS）、其他延伸因子、RNA聚合酶亚单位和染色质相关蛋白的基因突变，使S。酿酒酵母对药物6-氮尿嘧啶和霉酚酸敏感。这些药物是IMP脱氢酶（IMPDH）的抑制剂，IMP脱氢酶是鸟嘌呤核苷酸合成从头途径中的关键酶。它的丰度与从酵母到人类的真核生物中的细胞生长呈正相关。药物处理的酵母通过其四个IMPDH基因之一的转录诱导来应答。这种反应依赖于最佳功能的伸长机制。在人类中，免疫应答期间的T淋巴细胞增殖高度依赖于IMPDH合成。霉酚酸抑制T细胞增殖，是一种重要的临床免疫抑制剂，可抑制肾移植（和其他）患者的移植物排斥反应。IMPDH的突变也与视网膜色素变性的病因有关。 必需的酵母IMPDH基因家族的调节通过感知核苷酸库的细胞机制介导。该项目将使用生物化学和遗传学来了解IMPDH转录通过新的DNA元件的调节。一个序列是一个有效的抑制元件，它包含转录起始位点，并可调节延伸。酵母含有复杂的IMPDH同种型家族，对麦考酚酸抑制具有不同的敏感性。IMPDH形成耐药和敏感亚基之间的异聚体复合物的潜力将得到解决。缺乏IMPDH基因的酵母的药物敏感表型将有助于研究人类的耐药和敏感形式。鉴于霉酚酸酯在移植患者中的广泛应用和终身治疗，对IMPDH靶向药物的耐药性是一个重要的临床问题。将检查正常T细胞和来自接受治疗的患者的T细胞通过改变IMPDH表达和活性来响应药物的能力。不同个体的反应之间的差异将被量化。这对于理解治疗效果和患者对靶向IMPDH的免疫抑制剂的反应性的潜在遗传差异的长期目标将是重要的。

DESCRIPTION (provided by applicant): The elongation of transcripts by RNA polymerase II is a complex process dependent upon nucleotide substrate levels, elongation factors, and co-transcriptional events such as splicing. Mutations in genes encoding elongation factor SI I (TFIIS), other elongation factors, RNA polymerase subunits, and chromatin related proteins, render S. cerevisiae sensitive to the drugs 6-azauracil and mycophenolic acid. These drugs are inhibitors of IMP dehydrogenase (IMPDH) which is a critical enzyme in the de novo pathway of guanine nucleotide synthesis. Its abundance is positively correlated with cell growth in eukaryotes from yeast to humans. Drug treated yeast respond by transcriptional induction of one of their four IMPDH genes. The response is reliant upon an optimally functioning elongation machinery. In humans, T lymphocyte proliferation during an immune response is highly dependent upon IMPDH synthesis. Mycophenolic acid inhibits T cell proliferation and is an important clinical immunosuppressant that inhibits graft rejection in kidney transplant (and other) patients. Mutations in IMPDH have also been implicated in the etiology of retinitis pigmentosa. Regulation of the essential yeast IMPDH gene family is mediated through a cellular mechanism that senses nucleotide pools. This project will use biochemistry and genetics to understand this regulation of IMPDH transcription through novel DNA elements. One sequence is a potent repressive element which encompasses the transcription start site and may regulate elongation. Yeast contain a complex family of IMPDH isoforms with varying sensitivity to mycophenolic acid inhibition. The potential of IMPDH to form heteromeric complexes between drug resistant and sensitive subunits will be addressed. The drug sensitive phenotype of yeast lacking their IMPDH genes will be useful in studying resistant and sensitive forms in humans. Resistance to IMPDH-directed drugs is an important clinical issue given the wide spread and lifelong treatment of transplant patients with mycophenolate. The ability of normal T cells, and T cells from patients receiving therapy, to respond to the drug by altering IMPDH expression and activity, will be examined. Differences between the responses of different individuals will be quantified. This will be important for the long term goal of understanding potential genetic differences in the efficacy of therapy and responsiveness of patients to immunosuppressants that target IMPDH.