Namjilsuren Sanchirmaa, Arndt Karen M
Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
bioRxiv. 2025 Sep 3:2025.09.03.674035. doi: 10.1101/2025.09.03.674035.
The mechanisms that control the dynamic composition of RNAPII elongation complexes govern major transitions in the transcription cycle yet are poorly understood. Here, we show that the transcription elongation factor Spt5 determines elongation complex composition to promote productive elongation and the transition to termination. Using an unbiased genetic screen and genomic approaches in , we provide evidence that dephosphorylation of the Spt5 C-terminal repeat domain (CTR) by the Glc7/PP1 phosphatase is required to dislodge Paf1C from RNAPII near the cleavage and polyadenylation site (CPS). Mutations in Paf1C or the Spt5 CTR that dissociate Paf1C from RNAPII bypass the requirement for two critical regulatory subunits of Glc7. Depletion of Glc7 causes aberrant retention of Paf1C past the CPS and increased readthrough transcription, which is fully suppressed by Paf1C mutations. We conclude that Paf1C antagonizes termination and Glc7-mediated restructuring of the RNAPII elongation complex is a critical step in transcription termination.
控制RNA聚合酶II（RNAPII）延伸复合物动态组成的机制主导着转录周期中的主要转变，但目前对此了解甚少。在此，我们表明转录延伸因子Spt5决定延伸复合物的组成，以促进高效延伸以及向终止的转变。通过在……中使用无偏向性遗传筛选和基因组方法，我们提供证据表明，Glc7/PP1磷酸酶对Spt5 C末端重复结构域（CTR）的去磷酸化是将Paf1C从切割和聚腺苷酸化位点（CPS）附近的RNAPII上移除所必需的。Paf1C或Spt5 CTR中的突变使Paf1C与RNAPII解离，从而绕过了对Glc7两个关键调节亚基的需求。Glc7的缺失导致Paf1C在CPS之后异常保留，并增加通读转录，而Paf1C突变可完全抑制这种情况。我们得出结论，Paf1C拮抗终止，并且Glc7介导的RNAPII延伸复合物的重组是转录终止中的关键步骤。
