Structural basis of bacterial σ28-mediated transcription reveals roles of theRNApolymerase zinc-binding domain
Structural basis of bacterial σ28-mediated transcription reveals roles of theRNApolymerase zinc-binding domain
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DOI：
10.15252/embj.2020104389
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发表时间：
2020-06-02
期刊：
影响因子：
11.4
通讯作者：
Liu, Bin
中科院分区：
文献类型：
--
作者：
Shi, Wei;Zhou, Wei;Liu, Bin
在细菌中，sigma（28）是鞭毛特异性sigma因子，其靶向RNA聚合酶（RNAP）以控制涉及细菌运动性和趋化性的鞭毛相关基因的表达。然而，sigma（28）依赖性启动子识别的结构机制仍然没有表征。本文报道了E.大肠杆菌sigma（28）依赖性转录复合物的完整鞭毛特异性启动子。这些结构揭示了sigma（28）-RNAP如何通过与-10元件的强相互作用而与-35元件的弱接触来识别启动子DNA，从而启动转录。此外，我们观察到一个独特的结构，其中RNAP的β '锌结合结构域（ZBD）从其典型位置延伸出来，与上游非模板链相互作用。进一步的体外和体内试验表明，这种相互作用具有通过补偿σ 4和-35元件之间的弱相互作用而促进RNAP-启动子复合物的封闭到开放异构化的总体效果。这表明ZBD定位可能是sigma（70）家族因子增强具有弱sigma 4/-35元件相互作用的启动子的转录的一般机制。
In bacteria, sigma(28)is the flagella-specific sigma factor that targetsRNApolymerase (RNAP) to control the expression of flagella-related genes involving bacterial motility and chemotaxis. However, the structural mechanism of sigma(28)-dependent promoter recognition remains uncharacterized. Here, we report cryo-EMstructures ofE. coli sigma(28)-dependent transcribing complexes on a complete flagella-specific promoter. These structures reveal how sigma(28)-RNAPrecognizes promoterDNAthrough strong interactions with the -10 element, but weak contacts with the -35 element, to initiate transcription. In addition, we observed a distinct architecture in which the beta ' zinc-binding domain (ZBD) ofRNAPstretches out from its canonical position to interact with the upstream non-template strand. Furtherin vitroandin vivoassays demonstrate that this interaction has the overall effect of facilitating closed-to-open isomerization of theRNAP-promoter complex by compensating for the weak interaction between sigma 4 and -35 element. This suggests thatZBDrelocation may be a general mechanism employed by sigma(70)family factors to enhance transcription from promoters with weak sigma 4/-35 element interactions.