Replication Restart after Replication-Transcription Conflicts Requires RecA in Bacillus subtilis

Abstract

Head-on conflicts between replication and transcription occur when a gene is expressed from the lagging strand. These encounters stall the replisome and potentially break the DNA. We investigated the necessary mechanisms for Bacillus subtilis cells to overcome a site-specific engineered conflict with transcription of a protein-coding gene. We found that the recombination proteins RecO and AddAB both load RecA onto the DNA in response to the head-on conflict. Additionally, RecA loading by one of the two pathways was required for both replication restart and efficient survival of the collision. Our findings suggest that both single-strand gaps and double-strand DNA breaks occur at head-on conflict regions and demonstrate a requirement for recombination to restart replication after collisions with transcription.