Dual-specificity kinase; required for SPB duplication and mitotic and meiotic spindle checkpoints; triggers formation of force-generating kinetochore-microtubule (MT) attachments to promote kinetochore bi-orientation in MI; activation loop autophosphorylation enhances kinase activity; substrates include SPB proteins (Spc42p, Spc110p, Spc98p), MEN protein Mob1p, kinetochore protein Cnn1p, checkpoint protein Mad1p, and MT stabilization factor Stu1p; substrate of APCC(Cdh1); similar to human TTK