YwqL (EndoV), ExoA and PolA act in a novel alternative excision pathway to repair deaminated DNA bases in Bacillus subtilis.

摘要: DNA deamination generates base transitions and apurinic/apyrimidinic (AP)-sites which are potentially genotoxic cytotoxic. In Bacillus subtilis uracil can be removed from by the DNA-glycosylase through excision repair pathway. Genetic evidence suggests that B. YwqL, a homolog of Endonuclease-V (EndoV), acts on wider spectrum deaminated bases but factors complete this pathway have remained elusive. Here, we report purified His6-YwqL (hereafter BsEndoV) protein had in vitro endonuclease activity against double-stranded DNAs containing single (U), hypoxanthine (Hx), xanthine (X) or an AP site. Interestingly, while BsEndoV catalyzed strand break at second phosphodiester bond towards 3'-end U lesions, there was additional cleavage preceding Hx X lesions. Remarkably, event initiated X, completed recombinant His6-DNA polymerase A (BsPolA), not BsEndoV-processed For latter lesions performed His6-ExoA (BsExoA) necessary before completion their BsPolA. These results suggest existence novel alternative counteracts effects deamination. The presence vivo also supported analysis multiple deletions exoA, endoV polA spontaneous mutations growing cells, sensitivity wild-type mutant cells to deaminating agent.