Rtf1 is a conserved RNA polymerase II (RNAPII) elongation factor that promotes cotranscriptional histone modification, RNAPII transcript elongation, and mRNA processing. Rtf1 function requires the phosphorylation of Spt5, an essential RNAPII processivity factor. Spt5 is phosphorylated within its C-terminal domain (CTD) by cyclin-dependent kinase 9 (Cdk9), the catalytic component of positive transcription elongation factor b (P-TEFb). Rtf1 recognizes phosphorylated Spt5 (pSpt5) through its Plus3 domain. Since Spt5 is a unique target of Cdk9 and Rtf1 is the only known pSpt5-binding factor, the Plus3/pSpt5 interaction is thought to be a key Cdk9-dependent event regulating RNAPII elongation. Here, we dissect Rtf1 regulation by pSpt5 in the fission yeast Schizosaccharomyces pombe We demonstrate that the Plus3 domain of Rtf1 (Prf1 in S. pombe) and pSpt5 are functionally distinct and that they act in parallel to promote Prf1 function. This alternate Plus3 domain function involves an interface that overlaps the pSpt5-binding site and that can interact with single-stranded nucleic acid or with the polymerase-associated factor (PAF) complex in vitro We further show that the C-terminal region of Prf1, which also interacts with PAF, has a similar parallel function with pSpt5. Our results elucidate unexpected complexity underlying Cdk9-dependent pathways that regulate transcription elongation.

中文翻译：

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Spt5磷酸化和Rtf1 Plus3域通过不同的机制促进Rtf1功能。

Rtf1是一种保守的RNA聚合酶II（RNAPII）延长因子，可促进共转录组蛋白修饰，RNAPII转录本延长和mRNA加工。Rtf1功能需要将必需的RNAPII合成因子Spt5磷酸化。Spt5在其C末端结构域（CTD）中被细胞周期蛋白依赖性激酶9（Cdk9）磷酸化，这是正转录延伸因子b（P-TEFb）的催化成分。Rtf1通过其Plus3域识别磷酸化的Spt5（pSpt5）。由于Spt5是Cdk9的唯一靶标，而Rtf1是唯一已知的pSpt5结合因子，因此Plus3 / pSpt5相互作用被认为是调节RNAPII延伸的关键Cdk9依赖性事件。在这里，我们在裂殖酵母裂殖酵母中剖析了pSpt5对Rtf1的调控。我们证明了Rtf1（Sr. pombe）和pSpt5在功能上是不同的，它们并行起作用以促进Prf1功能。这个备用Plus3结构域功能涉及一个与pSpt5结合位点重叠的界面，该界面可以在体外与单链核酸或与聚合酶相关因子（PAF）复合体相互作用。我们进一步表明，Prf1的C端区域它还与PAF交互，与pSpt5具有类似的并行功能。我们的研究结果阐明了调控转录延伸的Cdk9依赖途径的潜在复杂性。这个备用Plus3结构域功能涉及一个与pSpt5结合位点重叠的界面，该界面可以在体外与单链核酸或与聚合酶相关因子（PAF）复合体相互作用。我们进一步表明，Prf1的C端区域它还与PAF交互，与pSpt5具有类似的并行功能。我们的研究结果阐明了调控转录延伸的Cdk9依赖途径的潜在复杂性。这个备用Plus3结构域功能涉及一个与pSpt5结合位点重叠的界面，该界面可以在体外与单链核酸或与聚合酶相关因子（PAF）复合体相互作用。我们进一步表明，Prf1的C端区域它还与PAF交互，与pSpt5具有类似的并行功能。我们的研究结果阐明了调控转录延伸的Cdk9依赖途径的潜在复杂性。