title: Hyperrecombination in Streptococcus pneumoniae depends on an atypical mutY homologue.
abstract: The unusual behavior of the mutation ami36, which generates hyperrecombination in two point crosses, was previously attributed to a localized conversion process changing A/G mispairs into CG pairs. Although the mechanism was found to be dependent on the DNA polymerase I, the specific function responsible for this correction was still unknown. Analysis of the pneumococcal genome sequence has revealed the presence of an open reading frame homologous to the gene mutY of Escherichia coli. The gene mutY encodes an adenine glycosylase active on A/G and A/7,8-dihydro-8-oxoguanine (8-OxoG) mismatches, inducing their repair to CG and C/8-OxoG, respectively. Here we report that disrupting the pneumococcal mutY homologue abolishes the hyperrecombination induced by ami36 and leads to a mutator phenotype specifically enhancing AT-to-CG transversions. The deduced amino acid sequence of the pneumococcal MutY protein reveals the absence of four cysteines, highly conserved in the endonuclease III/MutY glycosylase family, which ligate a [4Fe-4S](2+) cluster. The actual function of this cluster is still intriguing, inasmuch as we show that the pneumococcal gene complements a mutY strain of E. coli.
authors.affiliation: Laboratoire de Microbiologie et Génétique Moléculaires, Université Paul Sabatier, Toulouse, France.
authors.forename: M M
authors.initials: MM
authors.lastname: Samrakandi
authors.forename: F
authors.initials: F
authors.lastname: Pasta
mesh_terms: D000595:Amino Acid Sequence; D020137:Base Pair Mismatch; D045647:DNA Glycosylases; D004260:DNA Repair; D004926:Escherichia coli / Q000235:genetics; D017353:Gene Deletion; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009154:Mutation; D009699:N-Glycosyl Hydrolases / Q000737:chemistry / Q000235:genetics*; D010641:Phenotype; D011995:Recombination, Genetic; D017386:Sequence Homology, Amino Acid; D013296:Streptococcus pneumoniae / Q000235:genetics* / Q000254:growth & development; D014169:Transformation, Bacterial
chemical_list: D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C061738:mutY adenine glycosylase