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Publication Abstract from PubMed

RbpA is a small non-DNA-binding transcription factor that associates with RNA polymerase holoenzyme and stimulates transcription in actinobacteria, including Streptomyces coelicolor and Mycobacterium tuberculosis. RbpA seems to show specificity for the vegetative form of RNA polymerase as opposed to alternative forms of the enzyme. Here, we explain the basis of this specificity by showing that RbpA binds directly to the principal sigma subunit in these organisms, but not to more diverged alternative sigma factors. Nuclear magnetic resonance spectroscopy revealed that, although differing in their requirement for structural zinc, the RbpA orthologues from S. coelicolor and M. tuberculosis share a common structural core domain, with extensive, apparently disordered, N- and C-terminal regions. The RbpA-sigma interaction is mediated by the C-terminal region of RbpA and sigma domain 2, and S. coelicolor RbpA mutants that are defective in binding sigma are unable to stimulate transcription in vitro and are inactive in vivo. Given that RbpA is essential in M. tuberculosis and critical for growth in S. coelicolor, these data support a model in which RbpA plays a key role in the sigma cycle in actinobacteria.

The actinobacterial transcription factor RbpA binds to the principal sigma subunit of RNA polymerase.,Tabib-Salazar A, Liu B, Doughty P, Lewis RA, Ghosh S, Parsy ML, Simpson PJ, O'Dwyer K, Matthews SJ, Paget MS Nucleic Acids Res. 2013 Apr 19. PMID:23605043^[1]

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