Activity and in vivo dynamics of Bacillus subtilis DisA are affected by RadA/Sms and by Holliday junction-processing...

Bacillus subtilis c-di-AMP synthase DisA and RecA-related RadA/Sms are involved in the repair of DNA damage in exponentially growing cells. We provide genetic evidence that DisA or RadA/Sms is epistatic to the branch migration translocase (BMT) RecG and the Holliday junction (HJ) resolvase RecU in response to DNA damage. We provide genetic evidence damage. Functional DisA-YFP formed dynamic foci in exponentially growing cells, which moved through the nucleoids at a speed compatible with a DNA-scanning mode. DisA formed more static structures in the absence of RecU or RecG than in wild type cells, while dynamic foci were still observed in cells lacking the BMT RuvAB. Purified DisA synthesizes c-di-AMP, but interaction with RadA/Sms or with HJ DNA decreases DisA-mediated c-di-AMP synthesis. RadA/Sms-YFP also formed dynamic foci in growing cells, but the foci moved throughout the cells rather than just on the nucleoids, and co-localized rarely with DisA-YFP foci, suggesting that RadA/Sms and DisA interact only transiently in unperturbed conditions. Our data suggest a model in which DisA moving along dsDNA indicates absence of DNA damage/replication stress via normal c-di-AMP levels, while interaction with HJ DNA/halted forks leads to reduced c-di-AMP levels and an ensuing block in cell proliferation. RadA/Sms may be involved in modulating DisA activities.