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Publication Abstract from PubMed

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 sigma factors to recognize and unwind promoter DNA. Gp79, a protein from Escherichia coli phage phiEco32, inhibits host sigma70-mediated transcription while simultaneously activating transcription through its own sigma 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 sigma displacement by gp79 and promoter recognition by gp36. Our findings show that the N-terminus of gp79 invades the RNA channel, effectively displacing sigma4. 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.

A phage transcription factor displaces the host sigma factor and stabilizes its own sigma factor.,Xu L, Liang L, Yuan L, Yao Y, Hua X, Feng Y Nucleic Acids Res. 2025 Jul 19;53(14):gkaf683. doi: 10.1093/nar/gkaf683. PMID:40682819^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.