Time-lapse microscopy reveals unique roles for kinesins during anaphase in budding yeast

The mitotic spindle is a complex and dynamic structure. Genetic analysis in budding yeast has identified two sets of kinesin-like motors, Cin8p and Kip1p, and Kar3p and Kip3p, that have overlapping functions in mitosis. We have studied the role of three of these motors by video microscopy of motor mutants whose microtubules and centromeres were marked with green fluorescent protein. Despite their functional overlap, each motor mutant has a specific defect in mitosis: cin8 Delta mutants lack the rapid phase of anaphase B, kip1 Delta mutants show defects in the slow phase of anaphase B, and kip3 Delta mutants prolong the duration of anaphase to the point at which the spindle becomes longer than the cell. The kip3 Delta and kip1 Delta mutants affect the duration of anaphase, but cin8 Delta does not.