title: Evidence that YycJ is a novel 5'-3' double-stranded DNA exonuclease acting in Bacillus anthracis mismatch repair.
abstract: The most important system for correcting replication errors that survive the built in editing system of DNA polymerase is the mismatch repair (MMR) system. We have identified a novel mutator strain yycJ in Bacillus anthracis. Mutations in the yycJ gene result in a spontaneous mutator phenotype with a mutational frequency and specificity comparable to that of MMR-deficient strains such as those with mutations in mutL or mutS. YycJ was annotated as a metallo-β-lactamase (MβL) super family member with unknown activity. In this study we carried out a biochemical characterization of YycJ and demonstrated that a recombinant YycJ protein possesses a 5'-3' exonuclease activity at the 5' termini and at nicks of double-stranded DNA. This activity requires a divalent metal cofactor Mn2+ and is stimulated by 5'-phosphate ends of duplex DNA. The mutagenesis of conserved amino acid residues revealed that in addition to the five MβL family conserved motifs, YycJ appears to have its specific motifs that can be used to distinguish YycJ from other closely related MβL family members. A phylogenetic survey showed that putative YycJ homologs are present in several bacterial phyla as well as in members of the Methanomicrobiales and Thermoplasmales from Archaea. We propose that YycJ represents a new group of MβL fold exonucleases, which is likely to act in the recognition of MMR entry point and subsequent removal of the mismatched base in certain MutH-less bacterial species.
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, and the Molecular Biology Institute, University of California, and the David Geffen School of Medicine, Los Angeles, CA 90095, USA.
authors.forename: Hanjing
authors.initials: H
authors.lastname: Yang
authors.forename: Madeline
authors.initials: M
authors.lastname: Yung
authors.forename: Lei
authors.initials: L
authors.lastname: Li
authors.forename: James A
authors.initials: JA
authors.lastname: Hoch
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Ryan
authors.forename: Upendra K
authors.initials: UK
authors.lastname: Kar
authors.forename: Puneet
authors.initials: P
authors.lastname: Souda
authors.forename: Julian P
authors.initials: JP
authors.lastname: Whitelegge
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Miller
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001408:Bacillus anthracis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D017124:Conserved Sequence; D053904:DNA Breaks, Single-Stranded; D053843:DNA Mismatch Repair; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D005090:Exodeoxyribonucleases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008345:Manganese / Q000378:metabolism; D008969:Molecular Sequence Data; D059645:Mutation Rate; D010802:Phylogeny; D001618:beta-Lactamases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D008345:Manganese; D005090:Exodeoxyribonucleases; D001618:beta-Lactamases