CENPH

CENP-H is a constitutive inner kinetochore protein that occupies a central position in the centromere assembly hierarchy: it requires CENP-A for its own localization but is itself essential for recruiting CENP-C and outer kinetochore components such as the Hec1/Nuf2 complex, thereby bridging inner centromeric chromatin to the microtubule-binding outer kinetochore (PMID:11500386, PMID:15713649, PMID:16875666). CENP-H forms a stable heterodimeric coiled-coil subcomplex with CENP-K and cooperates with CSPP1 to regulate kinetochore–microtubule dynamics and chromosome oscillation during mitosis (PMID:19381461, PMID:26378239). Loss of CENP-H causes chromosome missegregation, multipolar spindles, G2/M arrest, and activation of the intrinsic apoptosis pathway, establishing it as essential for faithful mitosis and embryonic viability (PMID:20573960, PMID:16875666). In mouse oocytes, CENP-H also protects cyclin B1 from APC/C^Cdh1-mediated degradation to permit meiotic G2/M transition (PMID:27993978).

1. 1999 Medium

   Identification of CENP-H as a constitutive kinetochore component established that beyond CENP-A/B/C a new coiled-coil protein maintained kinetochore association throughout the cell cycle, opening the question of its function.

   Evidence Immunofluorescence co-localization with anti-centromere antibody in mouse fibroblasts; domain analysis

   PMID:10488063

   Open questions at the time

   • No functional loss-of-function data yet
   • Interacting partners unknown
   • Relationship to other CENPs undefined
2. 2001 High

   Conditional knockout in chicken DT40 cells placed CENP-H downstream of CENP-A but upstream of CENP-C in the centromere assembly pathway, resolving the epistatic order of inner kinetochore construction.

   Evidence Conditional loss-of-function mutant in DT40 cells; immunocytochemistry for CENP-A and CENP-C localization

   PMID:11500386

   Open questions at the time

   • Mechanism by which CENP-H recruits CENP-C unknown
   • Connection to outer kinetochore not yet tested
3. 2005 High

   Discovery of a direct CENP-H–Hec1 interaction revealed how the inner kinetochore is physically coupled to the outer kinetochore Nuf2/Hec1 complex, answering how centromeric chromatin signals are transmitted to microtubule-binding elements.

   Evidence Yeast two-hybrid, reciprocal co-IP, and FRAP in chicken DT40 cells

   PMID:15713649

   Open questions at the time

   • Structural basis of the CENP-H–Hec1 interface unresolved
   • Regulation of this interaction during mitosis not explored
4. 2006 Medium

   RNAi depletion in human cells confirmed that CENP-H is required for proper chromosome alignment and kinetochore architecture, with loss causing multipolar spindles and reduced CENP-C/CENP-E recruitment, extending the DT40 findings to a mammalian system.

   Evidence siRNA knockdown in HEp-2 cells; immunofluorescence for kinetochore proteins

   PMID:16875666

   Open questions at the time

   • Why mitotic arrest is not triggered is unclear
   • Relationship between CENP-H loss and spindle multipolarity mechanism unresolved
5. 2007 Medium

   ChIP-chip at human neocentromeres showed CENP-H co-occupies discontinuous CENP-A chromatin domains together with CENP-C, providing the first direct chromatin-binding footprint and suggesting a looped higher-order kinetochore architecture.

   Evidence ChIP-on-chip at multiple resolutions on neocentromere-bearing cell lines

   PMID:17651496

   Open questions at the time

   • Whether CENP-H directly contacts DNA or is tethered through CENP-A nucleosomes not determined
   • Only neocentromeres examined
6. 2009 Medium

   Biochemical isolation of a stable CENP-H/CENP-K heterodimer with 1:1 stoichiometry identified the minimal structural unit within the inner kinetochore through which CENP-H is incorporated, answering how CENP-H is stabilized at kinetochores.

   Evidence Tandem affinity purification from HEK293 cells; bioinformatic coiled-coil analysis

   PMID:19381461

   Open questions at the time

   • No crystal structure of the heterodimer
   • How the CENP-H/K dimer integrates with larger CCAN assemblies not addressed
7. 2010 High

   Genetic studies in zebrafish demonstrated that cenph is essential for organismal viability: its loss causes chromosome missegregation, G2/M arrest, and p53-dependent apoptosis, establishing CENP-H as indispensable for mitotic fidelity during vertebrate development.

   Evidence Transposon insertion mutant; morpholino knockdown and mRNA rescue; p53 epistasis in zebrafish embryos

   PMID:20573960

   Open questions at the time

   • Whether the apoptosis is entirely p53-dependent or involves additional pathways not fully resolved
   • Tissue-specific requirements not examined
8. 2015 High

   Demonstration that CENP-H directly binds CSPP1 and that this interaction is required for kinetochore–microtubule stability and chromosome oscillation clarified how CENP-H regulates dynamic microtubule attachments beyond its structural scaffolding role.

   Evidence In vitro binding, co-IP, siRNA, live imaging of oscillation, and a competing cell-permeable peptide in human cells

   PMID:26378239

   Open questions at the time

   • Phosphoregulation of the CENP-H/CSPP1 interaction not investigated
   • Whether CSPP1 bridges to other microtubule-associated proteins through CENP-H unknown
9. 2016 Medium

   Discovery that CENP-H protects cyclin B1 from APC/C^Cdh1-mediated degradation in mouse oocytes revealed an unexpected non-kinetochore function in licensing meiotic G2/M transition, expanding the gene's role beyond chromosome segregation.

   Evidence Morpholino injection in mouse oocytes; cyclin B1 rescue; Western blot for APC/C pathway

   PMID:27993978

   Open questions at the time

   • Mechanism by which CENP-H shields cyclin B1 from APC/C^Cdh1 is unclear (direct binding vs. indirect)
   • Whether this function operates in somatic cells not tested
10. 2017 Medium

    Identification of a CENP-H–GOLPH3 interaction that attenuates mTORC1/2 signaling suggested a signaling regulatory function outside the kinetochore, though its physiological context remains narrow.

    Evidence Co-IP, GST/His pull-down, confocal microscopy, and mTOR pathway Western blots in colorectal cancer cells

    PMID:28819418

    Open questions at the time

    • Functional significance of CENP-H at the Golgi versus kinetochore not delineated
    • Whether CENP-H–GOLPH3 interaction occurs under physiological (non-cancer) conditions unknown
    • Mechanism of mTOR attenuation not defined

• How CENP-H integrates into the full CCAN network at atomic resolution, how its non-kinetochore functions (cyclin B1 protection, mTOR modulation) relate to its canonical kinetochore role, and whether post-translational modifications regulate its multiple interactions remain open questions.
• No high-resolution structure of the CENP-H/K heterodimer or its interface with Hec1
• Post-translational regulation of CENP-H largely unexplored
• Non-kinetochore functions lack mechanistic detail