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| Title | A phage transcription factor displaces the host σ factor and stabilizes its own σ factor. |
|---|---|
| Journal, issue, pages | Nucleic Acids Res, Vol. 53, Issue 14, Year 2025 |
| Publish date | Jul 19, 2025 |
 Authors | Liqiao Xu / Liang Liang / Linggang Yuan / Yue Yao / Xiaoting Hua / Yu Feng /  |
| PubMed Abstract | Phages are the most abundant self-replicating entities on earth, and understanding their transcriptional regulation can provide insights into bacterial gene expression mechanisms. The bacterial RNA ...Phages are the most abundant self-replicating entities on earth, and understanding their transcriptional regulation can provide insights into bacterial gene expression mechanisms. The bacterial RNA polymerase core enzyme interacts with various σ factors to recognize and unwind promoter DNA. Gp79, a protein from Escherichia coli phage phiEco32, inhibits host σ70-mediated transcription while simultaneously activating transcription through its own σ factor, gp36. The underlying mechanism of this unusual dual regulatory role has remained unclear. In this study, we present cryo-EM structures of E. coli RNA polymerase (RNAP) in complex with gp79, and of RNAP in complex with gp79, gp36, and a cognate promoter. Structural and biochemical analyses reveal the basis for σ displacement by gp79 and promoter recognition by gp36. Our findings show that the N-terminus of gp79 invades the RNA channel, effectively displacing σ4. Upon encountering gp36, the N-terminus of gp79 adopts a new conformation, binds to gp36, and stabilizes the RNAP-promoter open complex. These findings advance our understanding of phage transcriptional regulation and suggest potential applications for synthetic biology. |
 External links | Nucleic Acids Res / PubMed:40682819 / PubMed Central |
| Methods | EM (single particle) |
| Resolution | 3.4 - 5.5 Å |
| Structure data | EMDB-63697, PDB-9m7y: EMDB-63698, PDB-9m7z: |
| Source |
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 Keywords | TRANSCRIPTION / phage / transcription regulation / sigma factor / gp79 / gp36 |
escherichia phage phieco32 (virus)
escherichia coli (E. coli)