Yeast study finds cohesin suppresses unequal exchanges between sister chromatids at repetitive sequences

Research posted to bioRxiv from a yeast model system reports that the protein complex cohesin suppresses unequal sister chromatid exchange (USCE) between repetitive DNA sequences, adding a previously undercharacterised function to cohesin's well-established roles in genome stability.

Cohesin is known to tether sister chromatids together from DNA replication through to chromosome segregation at cell division. Its roles in preventing aneuploidy — by ensuring sister kinetochores attach to opposite spindle poles — and in biasing DNA repair towards sister chromatids rather than homologous chromosomes are well documented. The current preprint investigates whether cohesin additionally reduces the risk of misaligned recombination between repetitive sequences on the same pair of sister chromatids, a process that can generate copy-number changes and loss of heterozygosity.

The experimental results indicate that cohesin does act to suppress USCE at repetitive loci in yeast. The authors suggest this function may be relevant to understanding why mutations in cohesin subunits and cohesin-loading factors are frequently found in human cancers and in developmental syndromes such as Cornelia de Lange syndrome. As a preprint, these findings await peer review.