Bacillus subtilis DisA helps to circumvent replicative stress during spore revival

The mechanisms that allow to circumvent replicative stress, and to resume DNA synthesis are poorly understood in Bacillus subtilis. To study the role of the diadenylate cyclase DisA and branch migration translocase (BMT) RadA/Sms in restarting a stalled replication fork, we nicked and broke the circular chromosome of an inert mature haploid spore, damaged the bases, and measured survival of reviving spores. During undisturbed ripening, nicks and breaks should be repaired by pathways that do not invoke long-range end resection or genetic exchange by homologous recombination, after which DNA replication might be initiated. We found that DNA damage reduced the viability of spores that lacked DisA, BMT (RadA/Sms, RuvAB or RecG), the Holliday junction resolvase RecU, or the translesion synthesis DNA polymerases (PolY1 or PolY2). DisA and RadA/Sms, in concert with RuvAB, RecG, RecU, PolY1 or PolY2, are needed to bypass replication-blocking lesions. DisA, which binds to stalled or reversed forks, did not apparently affect initiation of PriA-dependent DNA replication in vitro. We propose that DisA is necessary to coordinate responses to replicative stress; it could help to circumvent damaged template bases that otherwise impede fork progression.