26S proteasome identified as mediator of cohesin removal via second meiotic pathway

Accurate chromosome segregation during meiosis depends on the tightly controlled removal of sister chromatid cohesion — the molecular glue that holds replicated chromosomes together until the correct moment of division. The canonical pathway involves cleavage of the cohesin complex by the endopeptidase separase, which is itself held in check by securin until the ubiquitin-proteasome system (UPS) triggers securin destruction.

A preprint posted to bioRxiv on 22 August 2026 now reports that the 26S proteasome plays a second, mechanistically distinct role in cohesin removal during meiosis II. Using separation-of-function mutants that selectively impair either the proteasome's catalytic core or its regulatory particle, the authors dissect two branches of parallel pathways operating during meiotic exit. Their data indicate that the UPS contributes not only to securin destruction but also to the priming of the cohesin kleisin subunit for removal — a function that had not previously been assigned to the proteasome.

The work advances understanding of the molecular choreography governing meiotic fidelity, with potential relevance to research into aneuploidy, reproductive genetics, and the basic mechanisms of genome stability. As a preprint, these findings have not yet undergone peer review.