The Bacillus subtilis Competence Transcription Factor, ComK, Overrides LexA-imposed Transcriptional Inhibition without Physically Displacing LexA

• Published in: The Journal of biological chemistry 2001-11, Vol.276 (46), p.42901-42907
• Main Authors: Hamoen, L W, Haijema, B, Bijlsma, J J, Venema, G, Lovett, C M
• Format: Article
• Language: English
• Subjects: Bacillus subtilis; Bacillus subtilis - chemistry; Bacillus subtilis - metabolism; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; Base Sequence; Binding Sites; Dose-Response Relationship, Drug; Hydroxyl Radical - metabolism; LexA protein; Molecular Sequence Data; Promoter Regions, Genetic; Protein Binding; Protein Conformation; Rec A Recombinases - genetics; Rec A Recombinases - metabolism; recA gene; Serine Endopeptidases - chemistry; Serine Endopeptidases - metabolism; transcription factor ComK; Transcription Factors - chemistry; Transcription Factors - metabolism; Transcription, Genetic
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M104407200

During the development of competence in Bacillus subtilis the recA gene is activated by the competence transcription factor, ComK, which is presumably required to alleviate the transcriptional repression of recA by LexA. To investigate the mechanism by which ComK activates recA transcription we examined the binding of ComK and LexA to the recA promoter in vitro . Using hydroxyl radical protection analyses to establish the location of ComK dimer-binding sites within the recA promoter, we identified four AT-boxes in a configuration unique for ComK-regulated promoters. Gel mobility shift experiments showed that all four ComK dimer-binding sites were occupied at ComK concentrations in the physiological range. In addition, occupation of all ComK-binding sites did not prevent LexA from binding to the recA promoter, despite the fact that the ComK and LexA recognition motifs partially overlap. Although ComK did not replace LexA from the recA promoter, in vitro transcription analyses indicated that the presence of ComK is sufficient to alleviate LexA repression of recA .