A single-strand specific lesion drives MMS-induced hyper-mutability at a double-strand break in yeast

DNA Repair (Amst). 2010 Aug 5;9(8):914-21. doi: 10.1016/j.dnarep.2010.06.005. Epub 2010 Jul 21.


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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • Cytosine / analogs & derivatives
  • Cytosine / metabolism
  • DNA Breaks, Double-Stranded / drug effects*
  • DNA Repair / genetics*
  • DNA, Single-Stranded / genetics
  • DNA, Single-Stranded / metabolism*
  • DNA-Directed DNA Polymerase / metabolism
  • Methyl Methanesulfonate / pharmacology*
  • Models, Genetic
  • Mutagenesis
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / metabolism


  • DNA, Single-Stranded
  • 3-methylcytosine
  • Cytosine
  • Methyl Methanesulfonate
  • DNA polymerase zeta
  • DNA-Directed DNA Polymerase