Fragile DNA motifs trigger mutagenesis at distant chromosomal loci in saccharomyces cerevisiae

PLoS Genet. 2013 Jun;9(6):e1003551. doi: 10.1371/journal.pgen.1003551. Epub 2013 Jun 13.


DNA sequences capable of adopting non-canonical secondary structures have been associated with gross-chromosomal rearrangements in humans and model organisms. Previously, we have shown that long inverted repeats that form hairpin and cruciform structures and triplex-forming GAA/TTC repeats induce the formation of double-strand breaks which trigger genome instability in yeast. In this study, we demonstrate that breakage at both inverted repeats and GAA/TTC repeats is augmented by defects in DNA replication. Increased fragility is associated with increased mutation levels in the reporter genes located as far as 8 kb from both sides of the repeats. The increase in mutations was dependent on the presence of inverted or GAA/TTC repeats and activity of the translesion polymerase Polζ. Mutagenesis induced by inverted repeats also required Sae2 which opens hairpin-capped breaks and initiates end resection. The amount of breakage at the repeats is an important determinant of mutations as a perfect palindromic sequence with inherently increased fragility was also found to elevate mutation rates even in replication-proficient strains. We hypothesize that the underlying mechanism for mutagenesis induced by fragile motifs involves the formation of long single-stranded regions in the broken chromosome, invasion of the undamaged sister chromatid for repair, and faulty DNA synthesis employing Polζ. These data demonstrate that repeat-mediated breaks pose a dual threat to eukaryotic genome integrity by inducing chromosomal aberrations as well as mutations in flanking genes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Chromosome Aberrations
  • Chromosomes / genetics*
  • DNA Breaks, Double-Stranded
  • Genomic Instability*
  • Inverted Repeat Sequences / genetics*
  • Mutagenesis
  • Nucleic Acid Conformation
  • Nucleotide Motifs / genetics*
  • Saccharomyces cerevisiae / genetics*
  • Trinucleotide Repeats / genetics