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Publication Abstract from PubMed

In bacteria, principal sigma factors (sigma70 or sigmaA) transcribe housekeeping genes required for cell viability. Although most principal sigma genes are transcribed by the RNA polymerase (RNAP) holoenzyme containing the principal sigma factor itself, an extracytoplasmic function (ECF) sigma factor (sigmaShbA) governs transcription of the principal sigma factor gene (hrdB) in two model Streptomycetes. Here, we employed a combination of cryo-electron microscopy (cryo-EM) and bioinformatics to decipher how sigmaShbA-RNAP holoenzymes govern the transcription of hrdB genes in Streptomyces. A cryo-EM structure of Streptomyces coelicolor sigmaShbA-RNAP-promoter open (RPo) complex was solved at 2.97 A resolution. In combination with in vitro transcription assays, we demonstrate the unique structural features used by the sigmaShbA to recognize the hrdB promoter and form a transcription bubble. All Streptomyces genomes (603) tagged as 'reference' were retrieved from NCBI Datasets. The conserved protein sequences and genomic neighborhoods, as well as the promoter consensus sequences of sigmaShbA and sigmaHrdB homologs, support that the principal sigmaHrdB being governed by the ECF sigmaShbA is a common feature in Streptomyces. Overall, these results provide detailed molecular insights into the transcription of the principal sigmaHrdB gene and pave the way for globally modulating Streptomyces cell viability.

Molecular basis of Streptomyces ECF sigmaShbA factors transcribing principal sigmaHrdB genes.,Liu G, Yang X, Yan W, Wang Y, Yu F, Zheng J Nucleic Acids Res. 2025 Apr 22;53(8):gkaf339. doi: 10.1093/nar/gkaf339. PMID:40272361^[1]

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