CEP63

CEP63 is a centrosomal scaffold protein essential for centriole duplication, mitotic regulation, and the DNA damage–spindle assembly checkpoint. It localizes to the proximal end of centrioles as part of a CEP57–CEP63–CEP152 ring complex, where it recruits PLK4 via CEP152 to initiate centriole biogenesis, and independently recruits CDK1 to centrosomes to regulate mitotic entry (PMID:23333316, PMID:24240477, PMID:21406398). ATM/ATR-dependent phosphorylation of CEP63 upon DNA damage causes its centrosomal delocalization, inhibiting spindle assembly, while APC/C-mediated ubiquitylation of CEP152 within the CEP152–CEP63–CEP57 complex releases CEP57 to promote mitotic microtubule nucleation (PMID:19182792, PMID:34878135). CEP63 undergoes liquid–liquid phase separation with CEP152 to self-assemble the pericentriolar scaffold, and its abundance is controlled by p62-dependent selective autophagy; loss of Cep63 in mice causes p53-dependent neural progenitor apoptosis leading to microcephaly and meiotic defects causing male infertility (PMID:33208041, PMID:27869116, PMID:26158450).

1. 2009 High

   Establishing that CEP63 is a centrosomal target of ATM/ATR kinases answered how DNA damage signals inhibit spindle assembly: phosphorylation of CEP63 at Ser560 delocalizes it from centrosomes, blocking spindle formation.

   Evidence In vitro kinase assays in Xenopus egg extract, S560A mutagenesis, and DT40 gene knockout with spindle assembly readout

   PMID:19182792

   Open questions at the time

   • Upstream regulators that direct ATM/ATR specifically to the centrosome were not identified
   • Whether phosphorylation of mammalian CEP63 at the equivalent site has the same outcome was not tested
2. 2011 High

   Demonstrating that CEP63 directly binds and recruits CDK1 to centrosomes revealed a second function—regulation of mitotic entry—distinct from its role in the DNA damage checkpoint, and explained how CEP63 overexpression drives centrosome amplification.

   Evidence Co-immunoprecipitation of CEP63–CDK1, RNAi knockdown causing polyploidization and mitotic skipping, pharmacological rescue with roscovitine

   PMID:21406398

   Open questions at the time

   • Whether CEP63-mediated CDK1 recruitment is regulated by the ATM/ATR phosphorylation pathway was not addressed
   • Structural basis of the CEP63–CDK1 interaction is unknown
3. 2013 High

   Identifying CEP57–CEP63–CEP152 as a defined ring complex at the proximal centriole, and showing that CEP63–CEP152 recruits PLK4, established the molecular pathway for centriole duplication initiation and distinguished CEP63-dependent (mother-centriole) from DEUP1-dependent (deuterosome) centriole biogenesis.

   Evidence Chemical crosslinking, superresolution microscopy (STED/SIM), Co-IP, knockdown/overexpression in cell lines and in vivo

   PMID:23333316 PMID:24240477

   Open questions at the time

   • How CEP63 versus DEUP1 is selected at distinct centriolar structures was not resolved
   • Stoichiometry of the ring complex was not determined
4. 2015 High

   Cep63-knockout mice revealed that centrosome dysfunction, not aberrant DNA damage signaling, drives p53-dependent neural progenitor apoptosis and microcephaly, and additionally showed that Cep63 is required for meiotic centrosome function and male fertility.

   Evidence Cep63-knockout mouse, Cep63/p53 double-knockout epistasis rescue, chromosome spreads, TUNEL assay

   PMID:26158450

   Open questions at the time

   • Whether p53 activation proceeds via the mitotic surveillance pathway (e.g., USP28–53BP1) was not tested
   • Contribution of centrosome loss versus chromosome entanglement to infertility was not separated
5. 2016 High

   Discovery that autophagy limits centrosome number by selectively degrading CEP63 via the p62 adaptor revealed a homeostatic mechanism controlling centrosome copy number through protein turnover.

   Evidence Autophagy-deficient and p62-knockout cells/mice, Co-IP of CEP63–p62, centrosome number quantification

   PMID:27869116

   Open questions at the time

   • The specific ubiquitin signal on CEP63 recognized by p62 was not identified
   • Whether autophagic degradation of CEP63 is cell-cycle regulated was not determined
6. 2020 High

   Placing CCDC57 upstream of CEP63 in the centriole duplication pathway and demonstrating that CEP63–CEP152 undergoes liquid–liquid phase separation to self-assemble the pericentriolar scaffold together explained how the ring complex is both anchored and physically organized at the centriole.

   Evidence BioID proximity mapping, superresolution imaging, in vitro reconstitution of CEP63–CEP152 LLPS with purified proteins, FRAP, 1,6-hexanediol perturbation, hydrophobic motif mutagenesis

   PMID:32402286 PMID:33208041

   Open questions at the time

   • How CCDC57 handoff to CEP63 is regulated during the cell cycle is unknown
   • Whether LLPS is essential for PLK4 recruitment or only for scaffold architecture was not tested
7. 2022 High

   Showing that APC/C ubiquitylates CEP152 within the CEP152–CEP63–CEP57 complex to release CEP57 for pericentrin interaction and microtubule nucleation explained how the ring complex is remodeled at mitosis to switch centrosome function from duplication to spindle assembly.

   Evidence Co-IP of APC/C–CEP152, in vivo ubiquitylation assays, centrosomal fractionation, functional epistasis with CEP57

   PMID:34878135

   Open questions at the time

   • Whether CEP63 is co-degraded or recycled upon CEP152 ubiquitylation was not resolved
   • Timing relative to PLK4 activity and centriole disengagement was not mapped
8. 2022 Medium

   An unexpected non-centrosomal function was reported in which CEP63 stabilizes FXR1 by inhibiting its K63-linked ubiquitylation, thereby promoting YAP1 expression in colorectal cancer cells.

   Evidence Co-IP, KH-domain mutant mapping, ubiquitination assays, xenograft models in colorectal cancer cells

   PMID:35989368

   Open questions at the time

   • Single-lab finding without independent replication
   • Whether the CEP63–FXR1 interaction occurs outside the cancer context is unknown
   • Relationship to centrosomal CEP63 pools was not addressed

• Key unresolved questions include: (1) the structural basis and stoichiometry of the CEP57–CEP63–CEP152 ring, (2) how cell-cycle signals coordinate CEP63 LLPS, autophagic degradation, and APC/C-mediated complex remodeling, and (3) whether CEP63's non-centrosomal function with FXR1 represents a physiologically significant activity.
• No high-resolution structure of the CEP57–CEP63–CEP152 complex
• No reconstitution integrating LLPS with cell-cycle-dependent phosphorylation
• Non-centrosomal roles have not been validated in vivo outside cancer xenografts