Division of Biosciences, Institute of Structural and Molecular Biology, University College London, London, UK.
Nat Commun. 2021 Sep 17;12(1):5524. doi: 10.1038/s41467-021-25669-2.
Recruitment of RNA polymerase and initiation factors to the promoter is the only known target for transcription activation and repression in archaea. Whether any of the subsequent steps towards productive transcription elongation are involved in regulation is not known. We characterised how the basal transcription machinery is distributed along genes in the archaeon Saccharolobus solfataricus. We discovered a distinct early elongation phase where RNA polymerases sequentially recruit the elongation factors Spt4/5 and Elf1 to form the transcription elongation complex (TEC) before the TEC escapes into productive transcription. TEC escape is rate-limiting for transcription output during exponential growth. Oxidative stress causes changes in TEC escape that correlate with changes in the transcriptome. Our results thus establish that TEC escape contributes to the basal promoter strength and facilitates transcription regulation. Impaired TEC escape coincides with the accumulation of initiation factors at the promoter and recruitment of termination factor aCPSF1 to the early TEC. This suggests two possible mechanisms for how TEC escape limits transcription, physically blocking upstream RNA polymerases during transcription initiation and premature termination of early TECs.
在古菌中，招募 RNA 聚合酶和起始因子到启动子是转录激活和抑制的唯一已知靶点。目前尚不清楚随后向有效转录延伸的任何步骤是否参与了调控。我们描述了古菌嗜热硫珠菌中基本转录机制在基因上的分布情况。我们发现了一个明显的早期延伸阶段，在此阶段，RNA 聚合酶依次招募延伸因子 Spt4/5 和 Elf1 形成转录延伸复合物（TEC），然后 TEC 进入有效的转录延伸。在指数生长期间，TEC 逃逸是转录输出的限速步骤。氧化应激导致 TEC 逃逸的变化与转录组的变化相关。因此，我们的研究结果表明，TEC 逃逸有助于基础启动子的强度，并促进转录调控。TEC 逃逸受损与启动子处起始因子的积累以及终止因子 aCPSF1 招募到早期 TEC 相关。这表明 TEC 逃逸限制转录的两种可能机制，即在转录起始期间物理上阻止上游 RNA 聚合酶，并使早期 TEC 过早终止。
