title: A single-strand specific lesion drives MMS-induced hyper-mutability at a double-strand break in yeast.
abstract: Localized hyper-mutability (LHM) can be important in evolution, immunity, and genetic diseases. We previously reported that single-strand DNA (ssDNA) can be an important source of damage-induced LHM in yeast. Here, we establish that the generation of LHM by methyl methanesulfonate (MMS) during repair of a chromosomal double-strand break (DSB) can result in over 0.2 mutations/kb, which is approximately 20,000-fold higher than the MMS-induced mutation density without a DSB. The MMS-induced mutations associated with DSB repair were primarily due to substitutions via translesion DNA synthesis at damaged cytosines, even though there are nearly 10 times more MMS-induced lesions at other bases. Based on this mutation bias, the promutagenic lesion dominating LHM is likely 3-methylcytosine, which is single-strand specific. Thus, the dramatic increase in mutagenesis at a DSB is concluded to result primarily from the generation of non-repairable lesions in ssDNA associated with DSB repair along with efficient induction of highly mutagenic ssDNA-specific lesions. These findings with MMS-induced LHM have broad biological implications for unrepaired damage generated in ssDNA and possibly ssRNA.
authors.affiliation: Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, NC 27709, United States.
authors.forename: Yong
authors.initials: Y
authors.lastname: Yang
authors.forename: Dmitry A
authors.initials: DA
authors.lastname: Gordenin
authors.forename: Michael A
authors.initials: MA
authors.lastname: Resnick
mesh_terms: D003596:Cytosine / Q000031:analogs & derivatives / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects*; D004260:DNA Repair / Q000235:genetics*; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D008741:Methyl Methanesulfonate / Q000494:pharmacology*; D008957:Models, Genetic; D016296:Mutagenesis; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism
chemical_list: D004277:DNA, Single-Stranded; C036386:3-methylcytosine; D003596:Cytosine; D008741:Methyl Methanesulfonate; C425929:DNA polymerase zeta; D004259:DNA-Directed DNA Polymerase