RecA, DisA and RadA/Sms Interplay Regulates Replication Fork Remodeling to Prevent Genome Instability

The Bacillus subtilis recombinase RecA, the DNA damage checkpoint and diadenylate cyclase (DAC) DisA, and the DNA helicase RadA/Sms are required to prevent a DNA replication stress. Moreover, recA, disA and radA are epistatic among them in response to DNA damage. We show that RecA filamented onto ssDNA interacts with and recruits DisA and RadA/Sms onto branched DNA intermediates. DisA inhibits the ATPase activity of RadA/Sms C13A by competing for single-stranded (ss) DNA, and by a protein-protein interaction also inhibits the helicase activity of RadA/Sms. RecA binds a reversed fork and facilitates RadA/Sms-mediated unwinding to restore a fork intermediate, but DisA inhibits it. Finally, RadA/Sms inhibits DisA DAC activity, but RecA counters this negative effect. We propose that RecA, DisA and RadA/Sms interactions, which are mutually exclusive, limit the remodeling of stalled replication forks. DisA, in concert with RecA and/or RadA/Sms, indirectly contributes to template switching or lesion bypass, prevents fork breakage, restores a replication fork with a lagging-strand gap, and facilitates the recovery of c-di-AMP levels to re-initiate cell proliferation.