The LSH/HELLS homolog Irc5 contributes to cohesin association with chromatin in yeast

Accurate chromosome segregation is essential for every living cell as unequal distribution of chromosomes during cell division may result in genome instability that manifests in carcinogenesis and developmental disorders. Irc5 from Saccharomyces cerevisiae is a member of the conserved Snf2 family of ATP-dependent DNA translocases and its function is poorly understood. Here, we identify Irc5 as a novel interactor of the cohesin complex. Irc5 associates with Scc1 cohesin subunit and contributes to cohesin binding to chromatin. Disruption of IRC5 decreases cohesin levels at centromeres and chromosome arms, causing premature sister chromatid separation. Moreover, reduced cohesin occupancy at the rDNA region in cells lacking IRC5 leads to the loss of rDNA repeats. We also show that the translocase activity of Irc5 is required for its function in cohesion pathway. Finally, we demonstrate that in the absence of Irc5 both the level of chromatin-bound Scc2, a member of cohesin loading complex, and physical interaction between Scc1 and Scc2 are reduced. Our results suggest that Irc5 is an auxiliary factor that is involved in cohesin association with chromatin.