Expression of the ATP‐dependent deoxyribonuclease of Bacillus subtilis is under competence‐mediated control

Transcription of the ATP‐dependent deoxynuclease operon (addAB), as monitored by means of an addAB–lacZ transcriptional fusion, has a low, constitutive level and is initiated from a σA type promoter. Transcription of addAB is independent of DNA‐damaging agents known to induce the SOS response in Bacillus subtilis. However, addAB transcription increased significantly during competence development. This competence‐specific induction was dependent on the gene products of srfA., degU and comK, but not on that of recA. Deletion analysis of the addAB promoter region demonstrated that the competence‐specific transcription induction requires DNA sequences located upstream of the addAB promoter that associated with ComK, the competence transcription factor. The latter finding indicates that a direct regulatory link exists between the establishment of the competent state and the synthesis of AddAB, required for recombination of internalized donor DNA.