Meiosis-specific functions of kinesin motors in cohesin removal and maintenance of chromosome integrity in budding yeast

Abstract

Kinesin motors provide the molecular forces at the kinetochore-microtubule interface and along the spindle to control chromosome segregation. During meiosis with the two rounds of microtubule assembly-disassembly, the roles of motor proteins remain unexplored. We observed that in contrast to mitosis Cin8 (kinesin 5) and Kip3 (kinesin 8) together are indispensable in meiosis. Examining the meiosis in cin8∆ kip3∆ cells, we detected chromosome breakage in the meiosis II cells. The double mutant exhibits delay in the cohesin removal and spindle elongation during anaphase I. Consequently, some cells abrogate meiosis II and form dyads while some, as they progress through meiosis II, cause defect in chromosome integrity. We believe that in the latter cells, an imbalance of spindle mediated force and simultaneous persistent cohesin on the chromosomes cause their breakage. We provide evidence that tension generated by Cin8 and Kip3 through microtubule cross-linking is essential for signaling efficient cohesin removal and maintenance of chromosome integrity during meiosis.SummaryMolecular motors generate forces that facilitate chromosome segregation. Unlike mitosis, in meiosis, two times chromosome segregation occur with twice microtubule assembly/disassembly. This work reports that the motor mediated forces are crucial for cohesin removal in meiosis and thus maintain genome integrity.