Centrosome maturation requires phosphorylation-mediated sequential domain interactions of SPD-5

Abstract

Centrosomes consist of two centrioles and the surrounding pericentriolar material (PCM). The PCM expands during mitosis in a process called centrosome maturation, in which PCM scaffold proteins play pivotal roles to recruit other centrosomal proteins. In Caenorhabditis elegans, the scaffold protein SPD-5 forms a PCM scaffold in a polo-like kinase 1 (PLK-1) phosphorylation-dependent manner. However, how phosphorylation of SPD-5 promotes PCM scaffold assembly is unclear. Here, we identified three functional domains of SPD-5 through in vivo domain analyses, and propose that sequential domain interactions of SPD-5 are required for mitotic PCM scaffold assembly. Firstly, SPD-5 is targeted to centrioles through a direct interaction between its centriole localization (CL) domain and the centriolar protein PCMD-1. Then, intramolecular and intermolecular interactions between the SPD-5 phospho-regulated multimerization (PReM) domain and the PReM association (PA) domain are enhanced by phosphorylation by PLK-1, which leads to PCM scaffold expansion. Our findings suggest that the sequential domain interactions of scaffold proteins mediated by PLK-1 phosphorylation is an evolutionarily conserved mechanism of PCM scaffold assembly.