CTD公司
生物
RNA聚合酶Ⅱ
转录因子ⅡD
转录因子II F
抄写(语言学)
转录因子ⅡE
RNA聚合酶Ⅱ全酶
细胞生物学
延伸系数
分子生物学
遗传学
核糖核酸
基因表达
RNA聚合酶
基因
发起人
核糖体
语言学
海洋学
哲学
地质学
作者
Susanne A. Schneider,Yi Pei,Stewart Shuman,Beate Schwer
摘要
An interaction network connecting mRNA capping enzymes, the RNA polymerase II (Pol II) carboxyl-terminal domain (CTD), elongation factor Spt5, and the Cdk7 and Cdk9 protein kinases is thought to comprise a transcription elongation checkpoint. A crux of this network is Spt5, which regulates early transcription elongation and has an imputed role in pre-mRNA processing via its physical association with capping enzymes. Schizosaccharomyces pombe Spt5 has a distinctive CTD composed of tandem nonapeptide repeats of the consensus sequence (1)TPAWNSGSK(9). The Spt5 CTD binds the capping enzymes and is a substrate for threonine phosphorylation by the Cdk9 kinase. Here we report that deletion of the S. pombe Spt5 CTD results in slow growth and aberrant cell morphology. The severity of the spt5-DeltaCTD phenotype is exacerbated by truncation of the Pol II CTD and ameliorated by overexpression of the capping enzymes RNA triphosphatase and RNA guanylyltransferase. These results suggest that the Spt5 and Pol II CTDs play functionally overlapping roles in capping enzyme recruitment. We probed structure-activity relations of the Spt5 CTD by alanine scanning of the consensus nonapeptide. The T1A change abolished CTD phosphorylation by Cdk9 but did not affect CTD binding to the capping enzymes. The T1A and P2A mutations elicited cold-sensitive (cs) and temperature-sensitive (ts) growth defects and conferred sensitivity to growth inhibition by 6-azauracil that was exacerbated by partial truncations of the Pol II CTD. The T1A phenotypes were rescued by a phosphomimetic T1E change but not by capping enzyme overexpression. These results imply a positive role for Spt5 CTD phosphorylation in Pol Il transcription elongation in fission yeast, distinct from its capping enzyme interactions. Viability of yeast cells bearing both Spt5 CTD T1A and Pol II CTD S2A mutations heralds that the Cdk9 kinase has an essential target other than Spt5 and Pol II CTD-Ser2.
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