Stu2 is required for plus-end directed chromosome transport along microtubules during metaphase in Saccharomyces cerevisiae

Chromosome alignment on the mitotic spindle, also referred to as congression, is facilitated by translocation of side-bound chromosomes along the microtubule surface, which allows the establishment of end-on attachment of kinetochores to microtubule plus ends. We use a reconstitution assay in lysates prepared from metaphase-arrested budding yeast to show that kinetochore translocation along the lateral surface of microtubules is dependent on Stu2, a homolog of vertebrate XMAP215. Stu2 tracks both growing and shrinking microtubule ends but also colocalizes with moving lattice-bound kinetochores. In cells, we observed that Stu2 depletion impairs chromosome biorientation during metaphase.