Fig. 7. Plk1 regulates Nlp transport and attachment to the centrosome. In interphase cells, Nlp is transported to the centrosomes by the dynein-dynactin motor complex. At the centrosome it then contributes to the attachment and nucleation of microtubules via the -tubulin ring complex (-TuRC). In mitosis, Plk1 phosphorylates Nlp and exerts a dual regulatory function. Phosphorylated Nlp is unable to interact with either (i) its binding partners at the centrosome or (ii) the dynein-dynactin motor complex. This dual action of Plk1 both promotes the release of Nlp from the centrosome and prevents its re-supply by the dynein-dynactin motor complex, and as a consequence Nlp redistributes into the cytoplasm during mitosis. Mitosis-specific -TuRC binding proteins (GTBPs) then replace Nlp at the centrosome as part of the centrosome maturation process required for the formation of the mitotic spindle.