ComW6 Stimulates Transcription of Pneumococcal Competence Genes in vitro

The alternative streptococcal sigma-factor and master competence regulator, sigma(X), stimulates transcription from competence promoters, in vitro. As the only known alternative sigma-factor in streptococci, sigma(X) expression is tightly controlled in each species and has a specific physiological role. Pneumococcal transformation also requires the DNA binding activity of ComW, a known sigma(X) activator and stabilizer. Mutations to the housekeeping sigma factor, sigma(A), partially alleviate the ComW requirement, suggesting that ComW is a key player in the sigma factor swap during the pneumococcal competence response. However, there is no evidence of a direct ComW - RNA polymerase interaction. Furthermore, if and how ComW functions directly at combox promoters is still unknown. Here we report that a DNA-binding ComW variant, Com Delta 6, can stimulate transcription from sigma(X) promoters in vitro.