Fission yeast Pcp1 links polo kinase-mediated mitotic entry to γ-tubulin-dependent spindle formation

The centrosomal pericentrin-related proteins play pivotal roles in various aspects of cell division; however their underlying mechanisms remain largely elusive. Here we show that fission-yeast pericentrin-like Pcp1 regulates multiple functions of the spindle pole body (SPB) through recruiting two critical factors, the γ-tubulin complex (γ-TuC) and polo kinase (Plo1). We isolated two pcp1 mutants (pcp1-15 and pcp1-18) that display similar abnormal spindles, but with remarkably different molecular defects. Both mutants exhibit defective monopolar spindle microtubules that emanate from the mother SPB. However, while pcp1-15 fails to localise the γ-TuC to the mitotic SPB, pcp1-18 is specifically defective in recruiting Plo1. Consistently Pcp1 forms a complex with both γ-TuC and Plo1 in the cell. pcp1-18 is further defective in the mitotic-specific reorganisation of the nuclear envelope (NE), leading to impairment of SPB insertion into the NE. Moreover pcp1-18, but not pcp1-15, is rescued by overproducing nuclear pore components or advancing mitotic onset. The central role for Pcp1 in orchestrating these processes provides mechanistic insight into how the centrosome regulates multiple cellular pathways.