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An SI3-σ arch stabilizes cyanobacteria transcription initiation complex

Lookup NU author(s): Giorgio Lai, Maria Puiu, Dr Yulia YuzenkovaORCiD

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Abstract

Multisubunit RNA polymerases (RNAPs) associate with initiation factors (σ in bacteria) to start transcription. The σ factors are responsible for recognizing and unwinding promoter DNA in all bacterial RNAPs. Here, we report two cryo-EM structures of cyanobacterial transcription initiation complexes at near-atomic resolutions. The structures show that cyanobacterial RNAP forms an "SI3-σ" arch interaction between domain 2 of σA (σ2) and sequence insertion 3 (SI3) in the mobile catalytic domain Trigger Loop (TL). The "SI3-σ" arch facilitates transcription initiation from promoters of different classes through sealing the main cleft and thereby stabilizing the RNAP-promoter DNA open complex. Disruption of the "SI3-σ" arch disturbs cyanobacteria growth and stress response. Our study reports the structure of cyanobacterial RNAP and a unique mechanism for its transcription initiation. Our data suggest functional plasticity of SI3 and provide the foundation for further research into cyanobacterial and chloroplast transcription.

Publication metadata

Author(s): Shen L, Lai G, You L, Shi J, Wu X, Puiu M, Gu Z, Feng Y, Yuzenkova Y, Zhang Y

Publication type: Article

Publication status: Published

Journal: Proceedings of the National Academy of Sciences of the United States of America

Year: 2023

Volume: 120

Issue: 16

Print publication date: 18/04/2023

Online publication date: 10/04/2023

Acceptance date: 14/03/2023

Date deposited: 03/05/2023

ISSN (print): 0027-8424

ISSN (electronic): 1091-6490

Publisher: National Academy of Sciences

URL: https://doi.org/10.1073/pnas.2219290120

DOI: 10.1073/pnas.2219290120

PubMed id: 37036976

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