Deficiency of centromere-associated protein Slk19 causes premature nuclear migration and loss of centromeric elasticity

The cohesin complex prevents premature segregation of duplicated chromosomes by providing resistance to the pole-ward pull by spindle microtubules. The centromeric region (or sister kinetochores) bears the majority of this force and undergoes transient separation prior to anaphase, indicative of its elastic nature. A cysteine protease, separase, cleaves the cohesin subunit Scc1 and dissolves cohesion between sister chromatids, initiating their separation. Separase also cleaves the kinetochore protein SIk19 during anaphase. Slk19 has been implicated in stabilization of the mitotic spindle and regulation of mitotic exit, but it is not known what role it plays at the kinetochores. We show that during pre-anaphase arrest, the spindle in slk19 Delta cells is excessively dynamic and the nuclei move into mother-daughter junction prematurely.