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| Title | Structural basis for transcription activation by Crl through tethering of σ and RNA polymerase. |
|---|---|
| Journal, issue, pages | Proc Natl Acad Sci U S A, Vol. 116, Issue 38, Page 18923-18927, Year 2019 |
| Publish date | Sep 17, 2019 |
 Authors | Alexis Jaramillo Cartagena / Amy B Banta / Nikhil Sathyan / Wilma Ross / Richard L Gourse / Elizabeth A Campbell / Seth A Darst /  |
| PubMed Abstract | In bacteria, a primary σ-factor associates with the core RNA polymerase (RNAP) to control most transcription initiation, while alternative σ-factors are used to coordinate expression of additional ...In bacteria, a primary σ-factor associates with the core RNA polymerase (RNAP) to control most transcription initiation, while alternative σ-factors are used to coordinate expression of additional regulons in response to environmental conditions. Many alternative σ-factors are negatively regulated by anti-σ-factors. In , , and many other γ-proteobacteria, the transcription factor Crl positively regulates the alternative σ-regulon by promoting the association of σ with RNAP without interacting with promoter DNA. The molecular mechanism for Crl activity is unknown. Here, we determined a single-particle cryo-electron microscopy structure of Crl-σ-RNAP in an open promoter complex with a σ-regulon promoter. In addition to previously predicted interactions between Crl and domain 2 of σ (σ), the structure, along with -benzoylphenylalanine cross-linking, reveals that Crl interacts with a structural element of the RNAP β'-subunit that we call the β'-clamp-toe (β'CT). Deletion of the β'CT decreases activation by Crl without affecting basal transcription, highlighting the functional importance of the Crl-β'CT interaction. We conclude that Crl activates σ-dependent transcription in part through stabilizing σ-RNAP by tethering σ and the β'CT. We propose that Crl, and other transcription activators that may use similar mechanisms, be designated σ-activators. |
 External links | Proc Natl Acad Sci U S A / PubMed:31484766 / PubMed Central |
| Methods | EM (single particle) |
| Resolution | 3.26 Å |
| Structure data | EMDB-20090, PDB-6omf: |
| Chemicals |  ChemComp-MG:  ChemComp-ZN: |
| Source |
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 Keywords | TRANSCRIPTION / Transferase/DNA / Transcription-activator / DNA/RNA / SigmaS / beta' / Transferase-DNA complex |
Salmonella enterica subsp. enterica serovar Typhimurium (bacteria)
escherichia coli (E. coli)