The core-independent promoter-specific interaction of primary sigma factor

Previous studies have led to a model in which the promoter-specific recognition of prokaryotic transcription initiation factor, sigma (Sigma), is core dependent. Most Sigma functions were studied on the basis of this tenet. Here, we provide in vitro evidence demonstrating that the intact Bacillus subtilis primary sigma, Sigma(A), by itself, is able to interact specifically with promoter deoxyribonucleic acid (DNA), albeit with low sequence selectivity. The core-independent promoter-specific interaction of the Sigma(A) is -10 specific. However, the promoter -10 specific interaction is unable to allow the Sigma(A) to discern the optimal promoter spacing. To fulfill this goal, the Sigma(A) requires assistance from core RNA polymerase (RNAP). The ability of Sigma, by itself, to interact specifically with promoter might introduce a critical new dimension of study in prokaryotic Sigma function.