title: Mutagenesis dependent upon the combination of activation-induced deaminase expression and a double-strand break.
abstract: We explored DNA metabolic events potentially relevant to somatic hypermutation (SHM) of immunoglobulin genes using a yeast model system. Double-strand break (DSB) formation has been discussed as a possible component of the SHM process during immunoglobulin gene maturation. Yet, possible mechanisms linking DSB formation with mutagenesis have not been well understood. In the present study, a linkage between mutagenesis in a reporter gene and a double-strand break at a distal site was examined as a function of activation-induced deaminase (AID) expression. Induction of the DSB was found to be associated with mutagenesis in a genomic marker gene located 7 kb upstream of the break site: mutagenesis was strongest with the combination of AID expression and DSB induction. The mutation spectrum of this DSB and AID-mediated mutagenesis was characteristic of replicative bypass of uracil in one strand and was dependent on expression of DNA polymerase delta (Polδ). These results in a yeast model system illustrate that the combination of DSB induction and AID expression could be associated with mutagenesis observed in SHM. Implications of these findings for SHM of immunoglobulin genes in human B cells are discussed.
authors.affiliation: Laboratory of Structural Biology, National Institutes of Health, NIEHS, 111 T.W. Alexander Drive, PO Box 12233, MD F1-12, Research Triangle Park, NC 27709, USA.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Poltoratsky
authors.forename: Michelle
authors.initials: M
authors.lastname: Heacock
authors.forename: Grace E
authors.initials: GE
authors.lastname: Kissling
authors.forename: Rajendra
authors.initials: R
authors.lastname: Prasad
authors.forename: Samuel H
authors.initials: SH
authors.lastname: Wilson
mesh_terms: D026905:Amino Acid Transport Systems / Q000235:genetics; D001483:Base Sequence; D003564:Cytidine Deaminase / Q000096:biosynthesis*; D053903:DNA Breaks, Double-Stranded; D004252:DNA Mutational Analysis; D005656:Fungal Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D016296:Mutagenesis / Q000235:genetics*; D027041:Somatic Hypermutation, Immunoglobulin / Q000235:genetics*; D015003:Yeasts; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
chemical_list: D026905:Amino Acid Transport Systems; C097640:CAN1 protein, Candida albicans; D005656:Fungal Proteins; D000098830:AICDA (Activation-Induced Cytidine Deaminase); D003564:Cytidine Deaminase