Cell-cycle dependent phosphorylation of yeast pericentrin regulates γ-TuSC-mediated microtubule nucleation

Budding yeast Spc110, a member of gamma-tubulin complex receptor family (gamma-TuCR), recruits gamma-tubulin complexes to microtubule (MT) organizing centers (MTOCs). Biochemical studies suggest that Spc110 facilitates higher-order.-tubulin complex assembly (Kollman et al., 2010). Nevertheless the molecular basis for this activity and the regulation are unclear. Here we show that Spc110 phosphorylated by Mps1 and Cdk1 activates gamma-TuSC oligomerization and MT nucleation in a cell cycle dependent manner. Interaction between the N-terminus of the gamma-TuSC subunit Spc98 and Spc110 is important for this activity. Besides the conserved CM1 motif in gamma-TuCRs (Sawin et al., 2004), a second motif that we named Spc110/Pcp1 motif (SPM) is also important for MT nucleation. The activating Mps1 and Cdk1 sites lie between SPM and CM1 motifs. Most organisms have both SPM-CM1 (Spc110/Pcp1/PCNT) and CM1-only (Spc72/Mto1/Cnn/CDK5RAP2/myomegalin) types of gamma-TuCRs. The two types of gamma-TuCRs contain distinct but conserved C-terminal MTOC targeting domains.