Biology subjects

Nester, M. R.

Publications and source records attributed to Nester, M. R..

2 recordsLinked to original sources

bioRxiv2023

Double-strand breaks induce inverted duplication chromosome rearrangements by a DNA polymerase delta and Rad51-dependent mechanism

Inverted duplications, also known as foldback inversions, are commonly observed in cancers and are the major class of chromosome rearrangement recovered from yeast cells lacking Mre11 nuclease. Foldback priming at naturally occurring inverted repeats is one mechanism proposed for the generation of inverted duplications. However, the initiating lesion for these events and the mechanism by which they form has not been fully elucidated. Here, we show that a DNA double-strand break (DSB) induced near natural short, inverted repeats drives high frequency inverted duplication in Sae2 and Mre11-deficient cells. We find that DNA polymerase {delta} proof-reading activity acts non-redundantly with Rad1 nuclease to remove heterologous tails formed during foldback annealing. Additionally, Pol32 is required for the generation of inverted duplications, suggesting that Pol {delta} catalyzes fill-in synthesis primed from the foldback to create a hairpin-capped chromosome that is subsequently replicated to form a dicentric isochromosome. Stabilization of the dicentric chromosome after breakage involves telomere capture by non-reciprocal translocation mediated by repeat sequences and requires Rad51.

genetics↗

bioRxiv2022

Long-range DNA end resection supports homologous recombination by checkpoint activation rather than extensive homology generation

Homologous recombination (HR), the error-free mechanism for double-strand break (DSB) repair, relies on DNA end resection by nucleolytic degradation of the 5'-terminated ends. However, the role of long-range resection mediated by Exo1 and/or Sgs1-Dna2 in HR is not fully understood. Here, we show that Exo1 and Sgs1 are dispensable for recombination between closely-linked repeats but are required for interchromosomal repeat recombination in Saccharomyces cerevisiae. This requirement for long-range resection is coupled to DNA damage checkpoint activation and the need for checkpoint proteins. Furthermore, artificial activation of the checkpoint partially restores interchromosomal recombination to exo1{Delta} sgs1{Delta} cells. However, cell cycle delay is insufficient to rescue the interchromosomal recombination defect of exo1{Delta} sgs1{Delta} cells, suggesting an additional role for the checkpoint. Given that the checkpoint is necessary for DNA damage-induced chromosome mobility, we propose that the importance of the checkpoint, and therefore long-range resection, in interchromosomal recombination is due to a need to increase chromosome mobility to facilitate pairing of distant sites. The need for long-range resection is circumvented when the DSB and its repair template are in close proximity.

genetics↗