Rmi1 functions in S phase-mediated cohesion establishment via a pathway involving the Ctf18-RFC complex and Mrc1.

Saccharomyces cerevisiae RecQ helicase (Sgs1) combines with DNA topoisomerase III (Top3) and RecQ-mediated genome instability 1 (Rmi1) to form an evolutionarily conserved complex that is required for processing homologous recombination intermediates and restarting collapsed replication forks. It was previously reported that Rmi1 contributes to sister chromatid cohesion; however, the underlying molecular mechanism has been unclear. In the present study, Rmi1 was found to be enriched at the region close to an early-firing replication origin when replication forks were arrested near their origins in the presence of hydroxyurea. Genetic analyses revealed that Rmi1 promoted sister chromatid cohesion in a process that was distinct from both the cohesion establishment pathway involving Ctf4, Csm3, and Chl1 and the pathway involving the acetylation of Smc3. On the other hand, Rmi1 seemed to function in a pathway involving the Ctf18-RFC complex and Mrc1, which were previously predicted to regulate leading-strand DNA replication.