Abstact

During cell division, the nuclear mitotic apparatus protein (NuMA) orchestrates the focusing of microtubule minus-ends in spindle poles and cortical force generation on astral microtubules by interacting with dynein motors, microtubules and other cellular factors. Here we used in vitro reconstitution, cryo-electron microscopy and live-cell imaging to understand the mechanism and regulation of NuMA. We determined the structure of the processive dynein-dynactin-NuMA complex (DDN) and showed that the NuMA N terminus drives dynein motility in vitro and facilitates dynein-mediated transport in live cells. The C terminus of NuMA directly binds and suppresses the dynamics of the microtubule minus-end. Full-length NuMA is autoinhibited for its interactions with dynein and microtubules, whereas mitotically phosphorylated NuMA activates dynein in vitro and interphase cells. Together with dynein, activated full-length NuMA focuses microtubule minus-ends into aster-like structures. These results provide critical insights into the activation of NuMA and dynein for their mitotic functions.