Structural basis for transcription initiation by bacterial ECF σ factors.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 30858373.
- Also identified by DOI 10.1038/s41467-019-09096-y and PMC identifier 6411747.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Bacterial RNA polymerase employs extra-cytoplasmic function (ECF) σ factors to regulate context-specific gene expression programs. Despite being the most abundant and divergent σ factor class, the structural basis of ECF σ factor-mediated transcription initiation remains unknown. Here, we determine a crystal structure of Mycobacterium tuberculosis (Mtb) RNAP holoenzyme comprising an RNAP core enzyme and the ECF σ factor σ<sup>H</sup> (σ<sup>H</sup>-RNAP) at 2.7 Å, and solve another crystal structure of a transcription initiation complex of Mtb σ<sup>H</sup>-RNAP (σ<sup>H</sup>-RPo) comprising promoter DNA and an RNA primer at 2.8 Å. The two structures together reveal the interactions between σ<sup>H</sup> and RNAP that are essential for σ<sup>H</sup>-RNAP holoenzyme assembly as well as the interactions between σ<sup>H</sup>-RNAP and promoter DNA responsible for stringent promoter recognition and for promoter unwinding. Our study establishes that ECF σ factors and primary σ factors employ distinct mechanisms for promoter recognition and for promoter unwinding.
Medical subject headings
- Bacterial Proteins
- DNA-Directed RNA Polymerases
- Gene Expression Regulation, Bacterial
- Mycobacterium tuberculosis
- Sigma Factor
- Transcription Initiation, Genetic