Download MendeleyStructural basis of bacterial sigma28-mediated transcription reveals roles of the RNA polymerase zinc-binding domain.
Shi, W., Zhou, W., Zhang, B., Huang, S., Jiang, Y., Schammel, A., Hu, Y., Liu, B.(2020) EMBO J 39: e104389-e104389
- PubMed: 32484956
- DOI: https://doi.org/10.15252/embj.2020104389
- Primary Citation of Related Structures:
6PMI, 6PMJ - PubMed Abstract:
In bacteria, σ 28 is the flagella-specific sigma factor that targets RNA polymerase (RNAP) to control the expression of flagella-related genes involving bacterial motility and chemotaxis. However, the structural mechanism of σ 28 -dependent promoter recognition remains uncharacterized. Here, we report cryo-EM structures of E. coli σ 28 -dependent transcribing complexes on a complete flagella-specific promoter. These structures reveal how σ 28 -RNAP recognizes promoter DNA through 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 β' zinc-binding domain (ZBD) of RNAP stretches out from its canonical position to interact with the upstream non-template strand. Further in vitro and in vivo assays demonstrate that this interaction has the overall effect of facilitating closed-to-open isomerization of the RNAP-promoter complex by compensating for the weak interaction between σ4 and -35 element. This suggests that ZBD relocation may be a general mechanism employed by σ 70 family factors to enhance transcription from promoters with weak σ4/-35 element interactions.
Organizational Affiliation:
Section of Transcription & Gene Regulation, The Hormel Institute, University of Minnesota, Austin, MN, USA.
