Search, capture and signal: games microtubules and centrosomes play

Accurate distribution of the chromosomes in dividing cells requires couplin g of cellular polarity cues with both the orientation of the mitotic spindl e and cell cycle progression. Work in budding yeast has demonstrated that c ytoplasmic dynein and the kinesin Kip3p define redundant pathways that ensu re proper spindle orientation. Furthermore, it has been shown that the Kip3 p pathway components Kar9p and Bim1p (Yeb1p) form a complex that provides a molecular link between cortical polarity cues and spindle microtubules. Re cently, other studies indicated that the cortical localization of Kar9p dep ends upon actin cables and Myo2p, a type V myosin, In addition, a BUB2-depe ndent cell cycle checkpoint has been described that inhibits the mitotic ex it network and cytokinesis until proper centrosome position is achieved. Co mbined, these studies provide molecular insight into how cells link cellula r polarity, spindle position and cell cycle progression.