Discovery of a two protease DNA damage checkpoint recovery mechanism

The DNA damage response is a signaling pathway found throughout biology. In many bacteria the DNA damage checkpoint is enforced by inducing expression of a small, membrane bound inhibitor that delays cell division providing time to repair damaged chromosomes. How cells sense successful DNA repair and promote checkpoint recovery is unknown. By using a high-throughput, forward genetic screen, we identified two unrelated proteases, YlbL and CtpA, that promote DNA damage checkpoint recovery in Bacillus subtilis . Deletion of both proteases leads to accumulation of the checkpoint protein YneA. DNA damage sensitivity and increased cell elongation in protease mutants depends on yneA . Further, expression of YneA in protease mutants was sufficient to inhibit cell proliferation. Finally, we show that one of the two proteases, CtpA, directly cleaves YneA in vitro . With these results, we report the mechanism for DNA damage checkpoint recovery in bacteria that use membrane bound cell division inhibitors.