Template homology determines the genetics and mechanisms of gross chromosomal rearrangements in S. cerevisiae (736.11)

Abstract

Double strand breaks (DSBs) can lead to genome instability and cell death, and must be faithfully repaired. In Saccharomyces cerevisiae, DSBs are primarily repaired via homologous recombination (HR), which uses homologous sequence as a template for repair. Improper repair can result in gross chromosomal rearrangements (GCRs) such as translocations. Aberrant HR may occur when a template sequence with imperfect homology is used instead of completely homologous sequence. It is not known how divergent homologous sequences are selected as targets for non‐allelic HR, or which pathways suppress the formation of such GCRs. To examine this, we devised 3 separate genetic assays to detect GCRs mediated by a distinct sequence with imperfect homology to the rest of the genome. The assays differ from each other in both percent homology to their target sequences and number of potential rearrangement targets. We find that the GCR rates for these assays differ from each other as well as from existing assays. Additionally, the GCRs detected by the 3 assays exhibit diverse genetic requirements, responding differently to mutations affecting the HR pathways, HR between divergent sequences, and the DNA replication checkpoint. Finally, we characterized the products of the GCRs observed in the 3 assays. These results suggest that the homology between the recombination substrate and its rearrangement targets influences the mechanisms and genetics of GCR formation and the GCR spectrum.Grant Funding Source: NIH Grant GM26017