Cep152 interacts with the cryptic Polo-box of Plk4 and is required for Plk4-induced centriole overduplication.

SummaryCentriole duplication occurs once per cell cycle and requires Plk4, a member of the Polo-like kinase family. A key component of the centrosome is the c-tubulin ring complex (c-TuRC) that nucleates microtubules. GCP6 is a member of the c-TuRC, but its role in human cells and the regulation of its functions remain unclear. Here we report that depletion of human GCP6 prevents assembly of the c-TuRC and induces a high percentage of monopolar spindles. These spindles are characterized by a loss of centrosomal c-tubulin and reduced centriole numbers. We found that GCP6 is localized in the pericentriolar material but also at distal portions of centrioles. In addition, GCP6 is required for centriole duplication and Plk4-induced centriole overduplication. GCP6 interacts with and is phosphorylated by Plk4. Moreover, we find that Plk4-dependent phosphorylation of GCP6 regulates centriole duplication. These data suggest that GCP6 is a target of Plk4 in centriole biogenesis.

SummaryPolo-like kinases (Plks) perform crucial functions during mitosis, cytokinesis and centriole duplication. Plk2 is activated in early G1 phase and is involved in the reproduction of centrosomes. However, the mechanisms underlying Plk2-induced centriole duplication are incompletely understood. Here, we show that Plk2 directly targets the F-box protein F-box/WD repeat-containing protein 7 (Fbxw7), which is a regulator of the ubiquitin-mediated degradation of cyclin E. Plk2 phosphorylates Fbxw7 on serine 176 and the two proteins form a complex in vitro and in vivo. Phosphorylation of Fbxw7 by Plk2 induces destabilization of the F-box protein resulting in accumulation of cyclin E and increased potential for centriole reproduction. In addition, loss of Fbxw7 in human cells leads to uncontrolled centriole duplication, highlighting the importance of Fbxw7 regulation by Plk2. These findings define a previously unknown Plk2-dependent pathway involved at the onset of S phase and in centrosome duplication.