DNA double strand break end-processing and RecA induce RecN expression levels in Bacillus subtilis

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• DNA double-strand breaks (DSBs) pose a significant threat to genome stability.
• Bacillus subtilis employs complex DNA repair mechanisms to respond to DSBs.
• RecN protein is an early responder to DNA damage in B. subtilis.

Purpose of the Study:

• To elucidate the regulatory mechanisms governing RecN expression in Bacillus subtilis following DSBs.
• To differentiate between the SOS response and a distinct DSB response pathway.
• To identify key proteins and processes involved in modulating RecN levels.

Main Methods:

• Investigated RecN expression levels in Bacillus subtilis under various DNA damage conditions.
• Utilized genetic manipulation to assess the roles of RecA, RecO, LexA, SsbA, and end-processing activities.
• Analyzed protein turnover rates and filament formation in response to DSBs.

Main Results:

• RecN expression, not turnover, is upregulated in response to DSBs.
• End-processing activities and RecA protein contribute to increased RecN levels.
• RecO is essential for RecA filament formation and SOS induction but not for RecN expression.
• LexA absence and RecA/SsbA phosphorylation states do not significantly impact RecN levels.
• Two distinct pathways, SOS and DSB response, were identified for DSB repair.

Conclusions:

• Bacillus subtilis utilizes both SOS and DSB-specific responses to manage DNA double-strand breaks.
• The DSB response pathway relies on end-processing and RecA (or short RecO-independent RecA filaments).
• LexA is specifically required for the SOS response, not the general DSB response.
• These findings underscore the intricate regulation of DNA damage responses for maintaining genome integrity.