BUB-1 and CENP-C recruit PLK-1 to Control Chromosome Alignment and Segregation During Meiosis I inC. elegansOocytes

Abstract

Phosphorylation is a key post-translational modification that is utilised in many biological processes for the rapid and reversible regulation of protein localisation and activity. Polo-like kinase 1 (PLK-1) is essential for both mitotic and meiotic cell divisions, with key functions being conserved in eukaryotes. The roles and regulation of PLK-1 during mitosis have been well characterised. However, the discrete roles and regulation of PLK-1 during meiosis have remained obscure. Here, we used Caenorhabditis elegans (C. elegans) oocytes to show that PLK-1 plays distinct roles in meiotic spindle assembly/stability, chromosome alignment and segregation, and polar body extrusion during meiosis I. Furthermore, by a combination of live imaging and biochemical analysis we identified the chromosomal recruitment mechanisms of PLK-1 during C. elegans oocyte meiosis. The spindle assembly checkpoint kinase BUB-1 directly recruits PLK-1 to the kinetochore and midbivalent while the chromosome arm population of PLK-1 depends on a direct interaction with the centromeric-associated protein CENP-CHCP-4. We found that perturbing both BUB-1 and CENP-CHCP-4 recruitment of PLK-1 leads to severe meiotic defects, resulting in highly aneuploid oocytes. Overall, our results shed light on the roles played by PLK-1 during oocyte meiosis and provide a mechanistic understanding of PLK-1 targeting to meiotic chromosomes.

CENP-C-targeted PLK-1 regulates kinetochore function inC. elegansembryos

“…In contrast to the mechanistic understanding of kinetochore targeting, little is known about the roles and substrates in the different kinetochore subpopulations. Recruited by BUB1, outer kinetochore PLK1 regulates CDC20 phosphorylation and regulates the spindle assembly checkpoint 5 and mitosis timing 6 . In contrast, little is known about the role of inner-kinetochore PLK1.…”

“…Prometaphase and metaphase chromosomes are highlighted by cyan and yeloow arows, respectively. (C) Schematic indicating the PD motif characterised before 5 along with its mutant sequence (‘CENP-C PD mut ’), and the putative Mis12 and CENP-A interaction regions. (D) Fluorescently labelled PLK-1 was followed throughout mitosis in wild type and polo docking mutant CENP-C (‘ CENP-C PD mut ’ ).…”

“…Since CENP-C is required for kinetochore assembly and consequent BUB-1 kinetochore recruitment, this observation could be the trivial consequence of depleting BUB-1 from the kinetochore, which would in turn decrease PLK-1 levels 6 . We therefore took advantage of a CENP-C point mutant that disrupts its polo docking motif ('CENP-C PD mut ') and cannot target PLK-1 (Figure 1C) 5 . We found that kinetochore PLK-1 levels were significantly reduced in the CENP-C PD mut (Figure 1D, blue arrows).…”

“…We have recently identified HCP-4, the C. elegans orthologue of CENP-C, as a PLK1 (hereafter 'PLK-1') receptor 5 . We decided to assess whether CENP-C-targeted PLK-1 plays a role during mitosis and, if so, whether this differs from that of BUB-1-targeted PLK-1 6 .…”

A bifunctional kinase–phosphatase module balances mitotic checkpoint strength and kinetochore–microtubule attachment stability

“…Furthermore, in C. elegans , BUB1‐bound PLK1 phosphorylates the BUB1 ABBA motif to both enhance CDC20 binding and promote CDC20 dephosphorylation/activation, which together helps to activate the APC/C and allow timely mitotic exit (Houston et al , 2023). C. elegans BUB1 contains similar PLK1‐ and PP2A‐binding motifs to BUBR1, and these are important for chromosome alignment and segregation during meiosis I (Bel Borja et al , 2020; Taylor et al , 2023). Cross‐talk between PLK1 and PP2A has not been evaluated in worms, but it is notable that a PLK1 phosphorylation site is preserved in the PP2A‐B56‐binding site.…”