CENPQ

CENP-Q is a constitutive component of the CCAN that assembles as part of the CENP-O/P/Q/R/U sub-complex on kinetochores and is required for accurate chromosome alignment and segregation (PMID:16622419, PMID:23028590). It forms a stable heterodimer with CENP-U through its C-terminal half, and this interaction is mutually required for the stability and centromere localization of both proteins; loss of CENP-U abolishes kinetochore loading of the entire CENP-O complex (PMID:21454580, PMID:33660361, PMID:24481920). The CENP-OPQUR complex docks onto the CCAN at a joint interface formed by the CENP-HIKM and CENP-LN complexes, and is assembled step-wise on kinetochores during S-phase rather than pre-formed in the cytoplasm, with CENP-Q and CENP-U undergoing a maturation oligomerization step in late S-phase (PMID:23028590, PMID:30174292). Functionally, the disordered basic N-terminal tail of CENP-Q binds microtubules directly and cooperates with the KMN network to promote chromosome alignment (PMID:20228811, PMID:30174292). CENP-Q activity is phospho-regulated: Plk1 forms a ternary complex with PBIP1/CENP-U and phosphorylates CENP-Q at multiple sites, and timely Plk1-dependent phosphorylation drives delocalization of the PBIP1·CENP-Q complex from mitotic kinetochores as a prerequisite for normal M-phase progression (PMID:21454580, PMID:25670858). A separate phosphorylation event at S50 coordinates two distinct congression pathways—recruitment of CENP-E to kinetochores and a CENP-E-independent depolymerization-coupled pulling activity—without affecting Plk1 loading or CENP-O complex integrity (PMID:25395579). Conserved yeast orthologs (Okp1, Fta7) reinforce this role, acting as DNA-binding, multi-segmented nexus subunits that bridge the inner kinetochore to the outer KMN network (PMID:25135934, PMID:29046335).

1. 2006 High

   Established CENP-Q as a bona fide constitutive kinetochore protein by placing it within the CENP-A nucleosome distal (CAD) complex downstream of the CENP-A NAC, linking it to chromosome alignment and segregation.

   Evidence Co-IP, SILAC mass spectrometry, and RNAi knockdown with mitotic phenotype readout in human cells

   PMID:16622419

   Open questions at the time

   • Did not define CENP-Q's specific molecular activity within the complex
   • Assembly hierarchy and direct binding partners unresolved
2. 2010 Medium

   Provided the first biochemical evidence that CENP-Q can directly bind microtubules, hinting at a role in coupling centromeric chromatin to microtubule ends.

   Evidence In vitro microtubule binding assay

   PMID:20228811

   Open questions at the time

   • Microtubule-binding region not mapped
   • Single method reported briefly
   • Cellular relevance not yet demonstrated
3. 2011 High

   Defined the CENP-Q/CENP-U(PBIP1) heterodimer as mutually stabilizing and showed Plk1 forms a ternary complex with PBIP1 to phosphorylate CENP-Q and drive its delocalization, introducing phosphoregulation of CENP-Q at mitosis.

   Evidence Co-IP, phosphorylation assay, immunofluorescence, and RNAi in human cells

   PMID:21454580

   Open questions at the time

   • Did not enumerate all Plk1 phosphosites
   • Functional consequence of delocalization for segregation not fully resolved
4. 2012 High

   Resolved the topology and assembly dynamics of the CENP-O/P/Q/R/U sub-complex, showing it is built step-wise on kinetochores via CENP-L/CENP-K rather than pre-assembled, with a late-S-phase CENP-Q/CENP-U oligomerization maturation step.

   Evidence F3H, FRET, SNAP-tag, immunostaining, and FRAP in living mammalian cells

   PMID:23028590

   Open questions at the time

   • Molecular trigger for oligomerization unknown
   • Functional purpose of the maturation step not defined
5. 2014 High

   Demonstrated through yeast orthologs that the Okp1(CENP-Q)/Ame1(CENP-U) complex is DNA-binding and recruits the KMN network via an Ame1 motif, establishing the complex as a bridge between inner chromatin and outer kinetochore assembly.

   Evidence Biochemical reconstitution, point mutagenesis/genetic epistasis, structural and DNA-binding assays in budding yeast

   PMID:25135934

   Open questions at the time

   • Conservation of the Ame1 KMN-recruitment motif in human CENP-U not directly tested here
   • Specific contribution of Okp1/CENP-Q to DNA binding not isolated
6. 2014 Medium

   Showed CENP-U is required for kinetochore localization of the entire CENP-O complex including CENP-Q, fixing the dependency hierarchy for complex recruitment.

   Evidence Conditional knockout in mouse ES cells with immunofluorescence localization of CENP-O components

   PMID:24481920

   Open questions at the time

   • Did not address whether CENP-Q reciprocally affects CENP-U recruitment in all contexts
   • Mechanism of the localization dependency not structurally defined
7. 2014 High

   Identified S50 phosphorylation of CENP-Q as a regulatory switch coordinating two distinct chromosome congression pathways—CENP-E recruitment and CENP-E-independent depolymerization-coupled pulling—through a clean separation-of-function mutation.

   Evidence RNAi knockdown, S50A point mutation, live-cell imaging, and congression assays in human cells

   PMID:25395579

   Open questions at the time

   • Kinase responsible for S50 phosphorylation not identified
   • Mechanistic basis of depolymerization-coupled pulling unresolved
8. 2014 Medium

   Connected the CENP-Q ortholog Fta7 to CENP-A maintenance via Eic1/Mis18, linking the constitutive kinetochore network to new CENP-A loading in fission yeast.

   Evidence Co-IP, genetic analysis, and immunofluorescence in fission yeast

   PMID:24789708

   Open questions at the time

   • Whether this CENP-A maintenance link is conserved in human CENP-Q untested
   • Direct vs indirect nature of the association unclear
9. 2015 High

   Mapped at least nine Plk1-dependent phosphosites on CENP-Q and showed that both non-phosphorylatable and phosphomimetic mutants cause segregation defects, establishing that timely, balanced phosphorylation governs CENP-Q chromatin association and kinetochore residence.

   Evidence In vitro kinase assay, 9A/9D-E mutagenesis, chromatin fractionation, and segregation assays in human cells

   PMID:25670858

   Open questions at the time

   • Individual contributions of the nine sites not dissected
   • Phosphatase that reverses these sites unknown
10. 2017 High

    Crystallographic and topology mapping of the yeast ortholog revealed Okp1(CENP-Q) as a multi-segmented nexus with discrete binding sites for Ame1, Nkp1-Nkp2, and Ctf19-Mcm21, defining CENP-Q's architectural role as an inner kinetochore joint.

    Evidence Native MS, HDX-MS, X-ray crystallography, and genetic viability assays in K. lactis

    PMID:29046335

    Open questions at the time

    • Structure of the human CENP-Q complex not solved here
    • How these interfaces are remodeled during the cell cycle unaddressed
11. 2018 High

    Reconstitution of the human CCAN core localized the CENP-OPQUR complex to a CENP-HIKM/CENP-LN interface and demonstrated that the disordered basic N-terminal tail of CENP-Q binds microtubules and cooperates with KMN, functionally interchangeable with the NDC80 tail.

    Evidence Biochemical reconstitution of a 26-subunit kinetochore particle, in vitro microtubule binding, tail deletion/swap mutagenesis, and cellular alignment assays

    PMID:30174292

    Open questions at the time

    • In vivo regulation of the CENP-Q tail-microtubule interaction not fully defined
    • Relationship between tail microtubule binding and Plk1/S50 phosphoregulation unexplored
12. 2021 Medium

    Refined the recruitment logic of the complex, showing CENP-P and CENP-Q recruit CENP-U, which together with Bub1 redundantly recruits Plk1 to stabilize kinetochore-microtubule attachments, and that the human complex does not regulate Aurora B localization.

    Evidence siRNA depletion, kinase inhibitors, immunofluorescence, and epistasis in human cells

    PMID:34551298

    Open questions at the time

    • Direct CENP-Q contacts with Plk1 vs CENP-U-mediated not separated
    • Divergence from yeast COMA function mechanistically unexplained
13. 2021 Medium

    Mapped the domain architecture of the human complex, showing the C-terminal half of CENP-Q and residues 241-360 of CENP-U mediate the heterocomplex and its binding to CENP-O/P, with CENP-R engaging via CENP-U/CENP-Q.

    Evidence In vitro binding, Co-IP, and truncation/domain-mapping analysis

    PMID:33660361

    Open questions at the time

    • Residue-level interface not resolved
    • Single in vitro study without structural validation

• How CENP-Q's microtubule-binding tail, its multi-site Plk1 phosphoregulation, and S50-dependent congression control are integrated within a single kinetochore during error correction remains unresolved.
• Phosphatases reversing CENP-Q phosphorylation unidentified
• Kinase for S50 unknown
• No human structural model of the CENP-Q tail engaging microtubules in situ