A two-subunit bacterial sigma-factor activates transcription in Bacillus subtilis.
The sigma-like factor YvrI and coregulator YvrHa activate transcription from a small set of conserved promoters in Bacillus subtilis. We report here that these two proteins independently contribute sigma-region 2 and sigma-region 4 functions to a holoenzyme-promoter DNA complex. YvrI binds RNA polymerase (RNAP) through a region 4 interaction with the beta-subunit flap domain and mediates specific promoter recognition but cannot initiate DNA melting at the -10 promoter element. Conversely, YvrHa possesses sequence similarity to a conserved core-binding motif in sigma-region 2 and binds to the N-terminal coiled-coil element in the RNAP beta'-subunit previously implicated in interaction with region 2 of sigma-factors. YvrHa plays an essential role in stabilizing the open complex and interacts specifically with the N-terminus of YvrI. Based on these results, we propose that YvrHa is situated in the transcription complex proximal to the -10 element of the promoter, whereas YvrI is responsible for -35 region recognition. This system presents an unusual example of a two-subunit bacterial sigma-factor.
MacLellan
Shawn R
SR
Department of Microbiology, Cornell University, 370 Wing Hall, Ithaca, NY 14853-8101, USA.
Guariglia-Oropeza
Veronica
V
Gaballa
Ahmed
A
Helmann
John D
JD
D001412:Bacillus subtilis / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D011401:Promoter Regions, Genetic; D021122:Protein Subunits; D012808:Sigma Factor / Q000235:genetics* / Q000502:physiology; D015533:Transcriptional Activation
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D021122:Protein Subunits; D012808:Sigma Factor; D004247:DNA; D012321:DNA-Directed RNA Polymerases