CDCA2

CDCA2 (Repo-Man) is a PP1γ-targeting regulatory subunit that orchestrates chromatin dephosphorylation during mitotic exit and interphase to coordinate chromosome architecture, centromeric Aurora B localization, nuclear envelope reformation, and heterochromatin establishment. It recruits PP1γ to anaphase chromosomes to dephosphorylate histone H3 at T3, S10, and S28, thereby removing the CPC from chromosome arms to concentrate it at centromeres and enabling HP1 binding and H3K27me3-dependent heterochromatin formation; its N-terminal domain independently recruits Importin β, Nup153, and lamin A (via SUMOylation-dependent interaction) to reassemble the nuclear envelope, with PP1-mediated dephosphorylation of lamin A S22 required for proper lamina reassembly (PMID:16492807, PMID:21820363, PMID:21514157, PMID:28091603, PMID:35414260). Aurora B phosphorylation of CDCA2 at S893 excludes it from chromatin during prometaphase, and PP2A-mediated dephosphorylation of this site creates a bistable switch that governs its timely chromosomal loading at anaphase onset (PMID:23746640, PMID:32938714). Beyond mitosis, CDCA2 suppresses ATM-dependent DNA damage signaling by directing PP1 to dephosphorylate ATM, stabilizes MYC/MYCN and AURKA oncoproteins through inhibition of their ubiquitin-dependent degradation, and forms a transcriptional positive feedback loop as a direct MYC target gene (PMID:20188555, PMID:41844234, PMID:37196484).

1. 2006 High

   The identity of the factor that recruits PP1γ to chromatin at anaphase was unknown; discovery of CDCA2/Repo-Man as a selective PP1γ-chromatin targeting subunit established the molecular basis for mitotic exit dephosphorylation on chromosomes.

   Evidence Stable isotope labeling proteomics, PP1-binding domain mutagenesis, live-cell imaging, and RNAi in human cells

   PMID:16492807

   Open questions at the time

   • Structural basis of Repo-Man–PP1γ interaction not determined
   • Substrates beyond bulk chromatin not identified
2. 2006 High

   Whether Repo-Man–PP1 had downstream targets beyond chromatin was unclear; genetic epistasis showed it inactivates a condensin-dependent chromosome compaction activity (RCA) at anaphase, placing Repo-Man–PP1 in the condensin pathway.

   Evidence Conditional knockout in DT40 cells with live imaging and condensin depletion rescue

   PMID:16998479

   Open questions at the time

   • Molecular identity of the RCA substrate not defined
   • Whether this applies to mammalian somatic cells not shown
3. 2010 High

   Whether Repo-Man functions outside mitosis was unknown; biochemical reconstitution revealed that Repo-Man directly interacts with ATM and directs PP1-dependent dephosphorylation/inactivation of ATM, establishing a role in tuning the DNA damage checkpoint activation threshold.

   Evidence Xenopus egg extract biochemistry, co-immunoprecipitation, domain mutants, and RNAi in human cells

   PMID:20188555

   Open questions at the time

   • Whether ATM dephosphorylation occurs at physiological damage sites in vivo not resolved
   • Specific ATM phosphosites targeted by Repo-Man–PP1 not mapped
4. 2011 High

   The phosphatase responsible for removing histone H3T3 phosphorylation from chromosome arms—critical for CPC centromeric focusing—was unidentified; in vitro and cellular assays demonstrated that Repo-Man–PP1γ directly dephosphorylates H3T3, H3S10, and H3S28, and that this opposes Haspin to regulate Aurora B and MCAK chromosomal targeting.

   Evidence In vitro phosphatase assays, RNAi, immunofluorescence, dominant-negative and PP1-binding mutants; domain deletion/mutagenesis with live imaging and co-IP

   PMID:21514157 PMID:21820363

   Open questions at the time

   • Whether other PP1 targeting subunits contribute to arm H3T3 dephosphorylation not excluded
   • Quantitative contribution of each histone mark to CPC redistribution unclear
5. 2011 High

   How chromatin remodeling is coupled to nuclear envelope reformation was unclear; domain dissection showed that Repo-Man's N-terminal domain independently recruits Importin β and Nup153 to the chromosome periphery in a PP1-independent manner, physically linking histone dephosphorylation to nuclear envelope reassembly.

   Evidence Domain deletion/mutagenesis, live-cell imaging, co-immunoprecipitation, RNAi rescue

   PMID:21820363

   Open questions at the time

   • How Repo-Man N-terminal domain is spatially restricted to chromosome periphery not explained
   • Direct binding versus indirect recruitment of NE components not fully resolved
6. 2012 High

   Whether Repo-Man–PP1 acts at kinetochores during anaphase was unknown; an RNAi screen revealed that Repo-Man counteracts Aurora B phosphorylation of the outer kinetochore component Dsn1, and its depletion causes chromosome missegregation.

   Evidence RNAi screen with phosphorylation biosensor, immunofluorescence, live-cell imaging

   PMID:22801782

   Open questions at the time

   • Whether Repo-Man directly targets PP1 to kinetochores or acts indirectly not distinguished
   • Relative contribution of Repo-Man versus other PP1 targeting subunits (e.g., KNL1) at kinetochores not defined
7. 2013 High

   How Repo-Man's chromatin loading is temporally restricted to anaphase was unknown; identification of Aurora B phosphorylation at S893 as a chromatin-exclusion signal, reversed by PP2A, established a bistable switch mechanism governing Repo-Man's mitotic timing.

   Evidence Site-specific mutagenesis (S893), co-IP, phospho-specific antibodies, kinase/phosphatase assays

   PMID:23746640

   Open questions at the time

   • Whether additional phosphosites contribute to chromatin exclusion not systematically tested
   • Spatial distribution of PP2A activity relative to Aurora B gradient not mapped
8. 2017 High

   Whether Repo-Man–PP1 has interphase chromatin functions beyond checkpoint control was unknown; ChIP and fractionation studies showed it localizes to the nuclear periphery via Nup153 where it dephosphorylates H3S28 to promote HP1 binding and H3K27me3 deposition, establishing a direct role in heterochromatin formation and polycomb-mediated gene silencing.

   Evidence Chromatin fractionation, immunofluorescence, ChIP-seq, RNAi with rescue

   PMID:28091603

   Open questions at the time

   • Genome-wide identification of Repo-Man–dependent heterochromatin domains incomplete
   • Mechanism of specificity for peripheral versus internal heterochromatin not resolved
9. 2022 Medium

   How Repo-Man targets lamin A for dephosphorylation during NE reformation was unknown; SUMOylation of Repo-Man was shown to mediate its interaction with lamin A, and Repo-Man–PP1 dephosphorylates lamin A at S22, with SUMOylation-deficient mutants failing to rescue NE defects.

   Evidence In vivo and in vitro interaction assays, SUMOylation mutants, RNAi rescue, immunofluorescence

   PMID:35414260

   Open questions at the time

   • The SUMO E3 ligase responsible for Repo-Man SUMOylation not identified
   • Whether other lamin phosphosites are also Repo-Man–PP1 substrates not tested
   • Single-lab finding awaits independent confirmation
10. 2023 Medium

    Whether CDCA2 has PP1-independent oncogenic functions was unclear; CDCA2 was shown to stabilize AURKA by inhibiting SMURF1-mediated ubiquitination, with epistatic rescue demonstrating AURKA mediates CDCA2's pro-proliferative effects in melanoma.

    Evidence Co-immunoprecipitation, ubiquitination assay, protein stability assay, RNAi rescue, in vivo xenograft

    PMID:37196484

    Open questions at the time

    • Whether CDCA2 directly binds SMURF1 or AURKA not resolved
    • PP1 dependence of this stabilization mechanism not tested
    • Single cancer type studied
11. 2026 Medium

    Whether CDCA2 stabilizes other oncoproteins and is itself transcriptionally regulated by its targets was unknown; proximity ligation and ChIP studies revealed that CDCA2 stabilizes MYC and MYCN proteins and is a direct MYC transcriptional target, forming a positive feedback loop essential for viability in multiple cancer types.

    Evidence PLA, ChIP, promoter mutagenesis, degron-mediated depletion across TNBC, neuroblastoma, and colon cancer lines

    PMID:41844234

    Open questions at the time

    • Mechanism by which CDCA2 stabilizes MYC proteins (ubiquitin-dependent or not) not determined
    • Whether MYC stabilization requires PP1 activity not tested
    • Single-lab study

• Key open questions include: the structural basis of the Repo-Man–PP1γ holocomplex on chromatin, the full catalogue of Repo-Man–PP1 substrates genome-wide, the mechanism by which CDCA2 stabilizes oncoproteins (MYC, AURKA) and whether these require PP1 activity, and the in vivo physiological consequences of CDCA2 loss in organismal development.
• No crystal or cryo-EM structure of Repo-Man–PP1γ on nucleosomes
• Comprehensive substrate identification via phosphoproteomics not performed
• No knockout mouse or in vivo developmental phenotype reported