PDF(Pubmed)
Abstract：
RfaH, a paralog of the universally conserved NusG, binds to RNA polymerases (RNAP) and ribosomes to activate expression of virulence genes. In free, autoinhibited RfaH, an α-helical KOW domain sequesters the RNAP-binding site. Upon recruitment to RNAP paused at an ops site, KOW is released and refolds into a β-barrel, which binds the ribosome. Here, we report structures of ops-paused transcription elongation complexes alone and bound to the autoinhibited and activated RfaH, which reveal swiveled, pre-translocated pause states stabilized by an ops hairpin in the non-template DNA. Autoinhibited RfaH binds and twists the ops hairpin, expanding the RNA:DNA hybrid to 11 base pairs and triggering the KOW release. Once activated, RfaH hyper-stabilizes the pause, which thus requires anti-backtracking factors for escape. Our results suggest that the entire RfaH cycle is solely determined by the ops and RfaH sequences and provide insights into mechanisms of recruitment and metamorphosis of NusG homologs across all life.
摘要：
RfaH,普遍保守的NusG的模拟，与RNA聚合酶（RNAP）和核糖体结合以激活毒力基因的表达。在自由,自动抑制RfaH,α-螺旋KOW结构域螯合RNAP结合位点。在RNAP的招募暂停后，KOW被释放并重新折叠成β桶，结合核糖体。这里,我们报告了ops-paused转录延伸复合物的结构，并与自抑制和激活的RfaH结合，显示旋转，通过非模板DNA中的ops发夹稳定的预移位暂停状态。自动抑制的RfaH结合并扭曲了ops发夹，将RNA：DNA杂交体扩展到11个碱基对并触发KOW释放。一旦激活,RfaH超稳定了暂停，因此需要反回溯因素来逃避。我们的结果表明，整个RfaH周期仅由ops和RfaH序列决定，并提供了对所有生命中NusG同源物的募集和变态机制的见解。
