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首页> 外文期刊>Journal of Molecular Biology >Remodeling of the sigma(70) subunit non-template DNA strand contacts during the final step of transcription initiation
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Remodeling of the sigma(70) subunit non-template DNA strand contacts during the final step of transcription initiation

机译：在转录起始的最终步骤中重塑sigma（70）亚基非模板DNA链接触

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摘要

Transcription initiation in bacteria requires melting of similar to 13 bp of promoter DNA. The mechanism of the melting process is not fully understood. Escherichia coli RNA polymerase bearing a deletion of the beta subunit lobe I (amino acid residues 186-433) initiates melting of the - 10 promoter element but cannot propagate the melting downstream, towards the transcription initiation start site (+1). However, in the presence of nucleotides, stable downstream melting is induced. Here, we studied lacUV5 promoter complexes formed by the mutant enzyme by cross-linking RNA polymerase subunits to single-stranded DNA in the transcription bubble. In the absence of NTPs, a contact between the sigma(70) subunit and the non-template strand of the - 10 promoter element was detected. This contact disappeared in the presence of NTPs. Instead, a new sigma(70)-DNA contact as well as stable beta' and beta subunit contacts with the non-template DNA downstream of the -10 promoter element were established. In terms of the two-step (upstream initiation/ downstream propagation) model of promoter melting, our data suggest that beta lobe I induces the propagation of promoter melting by directing downstream promoter DNA duplex towards the downstream DNA-binding channel (beta' clamp). Establishment of downstream contacts leads to remodeling of upstream interactions between sigma(70) and the -10 promoter element that might facilitate promoter escape and sigma release. (c) 2005 Elsevier Ltd. All rights reserved.
机译：细菌中的转录起始需要融化约13 bp的启动子DNA。融化过程的机理尚不完全清楚。带有β亚基I的缺失（氨基酸残基186-433）的大肠杆菌RNA聚合酶启动了-10启动子元件的融化，但是不能向下游向转录起始起始位点（+1）传播融化。然而，在核苷酸的存在下，诱导了稳定的下游熔解。在这里，我们研究了由突变酶通过将RNA聚合酶亚基交联到转录气泡中的单链DNA上而形成的lacUV5启动子复合物。在没有NTP的情况下，检测到sigma（70）亚基与-10启动子元件的非模板链之间的接触。存在NTP时，此联系消失了。相反，建立了新的sigma（70）-DNA接触以及与-10启动子元件下游的非模板DNA稳定的beta'和beta亚基接触。就启动子融化的两步模型（上游启动/下游传播）而言，我们的数据表明，β叶I通过将下游启动子DNA双链体引向下游DNA结合通道（β'钳位）来诱导启动子融解的传播。 。下游接触的建立导致sigma（70）与-10启动子元件之间上游相互作用的重塑，这可能促进启动子逃逸和sigma释放。 （c）2005 Elsevier Ltd.保留所有权利。

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