1 research outputs found
Editing of misaligned 3ā²-termini by an intrinsic 3ā²ā5ā² exonuclease activity residing in the PHP domain of a family X DNA polymerase
Bacillus subtilis gene yshC encodes a family X DNA polymerase (PolXBs), whose biochemical features suggest that it plays a role during DNA repair processes. Here, we show that, in addition to the polymerization activity, PolXBs possesses an intrinsic 3ā²ā5ā² exonuclease activity specialized in resecting unannealed 3ā²-termini in a gapped DNA substrate. Biochemical analysis of a PolXBs deletion mutant lacking the C-terminal polymerase histidinol phosphatase (PHP) domain, present in most of the bacterial/archaeal PolXs, as well as of this separately expressed protein region, allow us to state that the 3ā²ā5ā² exonuclease activity of PolXBs resides in its PHP domain. Furthermore, site-directed mutagenesis of PolXBs His339 and His341 residues, evolutionary conserved in the PHP superfamily members, demonstrated that the predicted metal binding site is directly involved in catalysis of the exonucleolytic reaction. The implications of the unannealed 3ā²-termini resection by the 3ā²ā5ā² exonuclease activity of PolXBs in the DNA repair context are discussed