Recruitment of cohesin to heterochromatic regions by Swi6/HP1 in fission yeast.

Fission yeast centromeres, like those of higher eukaryotes, are composed of repeated DNA structures and associated heterochromatin protein complexes, that have a critical function in the faithful segregation of chromosomes during cell division. Cohesin protein complexes, which are essential for sister-chromatid cohesion and proper chromosome segregation, are enriched at centromeric repeats. We have identified a functional and physical link between heterochromatin and cohesin. We find that the preferential localization of cohesins at the centromeric repeats is dependent on Swi6, a conserved heterochromatin protein that is required for proper kinetochore function. Cohesin is also enriched at the mating-type heterochromatic region in a manner that depends on Swi6 and is required to preserve the genomic integrity of this locus. We provide evidence that a cohesin subunit Psc3 interacts with Swi6 and its mouse homologue HP1. These data define a conserved function of Swi6/HP1 in recruitment of cohesin to heterochromatic regions, promoting the proper segregation of chromosomes.