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-Structure paper
Title | Single-stranded DNA drives σ subunit loading onto mycobacterial RNA polymerase to unlock initiation-competent conformations. |
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Journal, issue, pages | Nucleic Acids Res, Vol. 53, Issue 7, Year 2025 |
Publish date | Apr 10, 2025 |
![]() | Rishi Kishore Vishwakarma / Nils Marechal / Zakia Morichaud / Mickaël Blaise / Emmanuel Margeat / Konstantin Brodolin / ![]() |
PubMed Abstract | Initiation of transcription requires the formation of the "open" promoter complex (RPo). For this, the σ subunit of bacterial RNA polymerase (RNAP) binds to the nontemplate strand of the -10 element ...Initiation of transcription requires the formation of the "open" promoter complex (RPo). For this, the σ subunit of bacterial RNA polymerase (RNAP) binds to the nontemplate strand of the -10 element sequence of promoters and nucleates DNA unwinding. This is accompanied by a cascade of conformational changes on RNAP, the exact mechanics of which remains elusive. Here, using single-molecule Förster resonance energy transfer and cryo-electron microscopy, we explored the conformational landscape of RNAP from the human pathogen Mycobacterium tuberculosis upon binding to a single-stranded DNA (ssDNA) fragment that includes the -10 element sequence (-10 ssDNA). We found that like the transcription activator RNAP-binding protein A, -10 ssDNA induced σ subunit loading onto the DNA/RNA channels of RNAP. This triggered RNAP clamp closure and unswiveling that are required for RPo formation and RNA synthesis initiation. Our results reveal a mechanism of ssDNA-guided RNAP maturation and identify the σ subunit as a regulator of RNAP conformational dynamics. |
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Methods | EM (single particle) |
Resolution | 3.2 - 4.33 Å |
Structure data | EMDB-50508, PDB-9fjp: ![]() EMDB-50509: cryo-EM structure of Mycobacterium tuberculosis sigma-B RNA polymerase bound to -10 promoter element ssDNA oligo - consensus map EMDB-50510, PDB-9fjr: EMDB-50511: Cryo-EM structure of Mycobacterium tuberculosis sigma-B RNA polymerase bound to -10 promoter element ssDNA oligo - sigma-B udocked conformation ![]() EMDB-50512: Cryo-EM structure of Mycobacterium tuberculosis sigma-B RNA polymerase bound to -10 promoter element ssDNA oligo - swiveled conformation ![]() EMDB-50514: Cryo-EM structure of Mycobacterium tuberculosis sigma-B RNA polymerase bound to -10 promoter element ssDNA oligo - unswiveled conformation |
Chemicals | ![]() ChemComp-ZN: ![]() ChemComp-MG: |
Source |
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![]() | TRANSCRIPTION / RNA polymerase; sigma factor; SigB / stress response; -10 promoter element; promoter recognition; tuberculosis |