Affinage

Showing CBX5 — HP1 is a alias.

CBX5

Chromobox protein homolog 5 · UniProt P45973

Length
191 aa
Mass
22.2 kDa
Annotated
2026-06-09
100 papers in source corpus 41 papers cited in narrative 41 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

CBX5/HP1α is a multivalent chromatin architectural protein that reads the H3K9me2/3 mark and dimerizes to crosslink nucleosomes, compact chromatin, and template phase-separated heterochromatin condensates (PMID:29336876, PMID:29339721, PMID:34106828). Selectivity for H3K9me3 nucleosomes emerges from the combined action of its chromo domain, hinge, and chromoshadow domain (which suppresses non-specific DNA binding) and is sharpened by CK2-mediated N-terminal phosphorylation that switches HP1α from promiscuous DNA binding to mark-specific nucleosome engagement and drives liquid-liquid phase separation (PMID:28636604, PMID:25332400, PMID:23142645, PMID:36537242). A cryo-EM structure shows a symmetric HP1α dimer bridging two H3K9me3 nucleosomes without contacting linker DNA, and acute degron studies establish that dimerization-dependent chromatin crosslinking, rather than transcription or local compaction, imparts mechanical stiffness to nuclei and mitotic chromosomes (PMID:29336876, PMID:34106828). HP1α scaffolds repressive machinery—SUV39H1/Rb at the cyclin E promoter, G9a coupled to DNMT1/3a, BRG1, and the ADNP/CHD4 ChAHP complex—to silence both heterochromatic and euchromatic targets, and it stabilizes H3K9 methyltransferases and demethylases on chromatin to maintain the epigenetic landscape (PMID:11484059, PMID:12711675, PMID:17470536, PMID:12411497, PMID:29795351, PMID:35166421). In mitosis HP1α is regulated by a methyl/phospho switch: Aurora B-catalyzed H3S10 phosphorylation ejects it from chromosome arms, while NDR1-mediated hinge phosphorylation targets a pool to kinetochores to support Sgo1 recruitment and the chromoshadow domain binds Haspin to protect centromeric cohesion; HP1 is itself an essential CPC component that activates Aurora B (PMID:16222246, PMID:24619172, PMID:26954544, PMID:29467217, PMID:29491004). HP1α further functions in genome maintenance, being recruited to DNA breaks via p150CAF-1 to promote end resection, BRCA1/BARD1 retention, and homologous recombination (PMID:21464229, PMID:25634209, PMID:23287531, PMID:23589625). Paralog-specific properties, encoded largely in the disordered regions, distinguish HP1α from HP1β/γ in mitotic retention, condensate behavior, and isoform-specific silencing during neuronal differentiation (PMID:10460410, PMID:33661100, PMID:17627279).

Mechanistic history

Synthesis pass · year-by-year structured walk · 20 steps
  1. 1999 Medium

    Established that HP1α is phosphorylated in a cell-cycle-dependent manner and uniquely retained at centromeres in mitosis, raising the question of paralog-specific heterochromatin function.

    Evidence Isoform-specific immunostaining and biochemical fractionation across cell-cycle stages in HeLa cells

    PMID:10460410

    Open questions at the time
    • Phosphosite and responsible kinase not identified
    • Functional consequence of centromeric retention not tested
  2. 2001 High

    Showed HP1α is recruited by Rb together with SUV39H1 to repress a euchromatic cell-cycle gene, extending HP1 function beyond constitutive heterochromatin.

    Evidence Co-IP and ChIP at the cyclin E promoter in fibroblasts

    PMID:11484059

    Open questions at the time
    • Direct vs. indirect contacts within the Rb-SUV39H1-HP1 complex not resolved
    • Generality across other Rb targets unclear
  3. 2002 Medium

    Defined biochemical determinants of HP1α partner selectivity and heterochromatin targeting, identifying isoform-specific BRG1 binding, TFIID interaction, and a hinge RNA-binding requirement.

    Evidence Co-IP, in vitro binding, mutagenesis, and immunofluorescence/RNA-binding assays in mammalian cells

    PMID:11959914 PMID:12231507 PMID:12411497

    Open questions at the time
    • RNA species bound by the hinge not identified
    • Quantitative contribution of each interaction to silencing unresolved
  4. 2003 Medium

    Linked H3K9 methylation reading to DNA methylation by showing HP1 directly binds DNMT1 and DNMT3a, suggesting cross-talk between the two repressive marks.

    Evidence In vitro binding, Co-IP, and co-purification of methyltransferase activity from nuclear extracts

    PMID:12711675

    Open questions at the time
    • Direct stimulation of DNMT activity by HP1 not quantified
    • Largely characterized for HP1β
  5. 2005 High

    Established the methyl/phospho switch: Aurora B phosphorylation of H3S10 ejects HP1 from mitotic chromatin without altering H3K9me3, explaining mitotic HP1 release.

    Evidence Cell fractionation, ChIP, and Aurora B inhibition/depletion in mitotic cells

    PMID:16222246

    Open questions at the time
    • Does not address centromeric HP1α retention seen earlier
    • Reassociation kinetics during mitotic exit not defined
  6. 2007 Medium

    Demonstrated an isoform-specific developmental role: HP1α enforces permanent silencing of E2F target genes in differentiating neurons, distinct from HP1γ.

    Evidence Isoform-specific knockdown/overexpression, ChIP at E2F sites, and in vivo cerebellar analysis

    PMID:17627279

    Open questions at the time
    • Mechanism of HP1γ-to-HP1α switch not defined
    • Upstream signals driving HP1α accumulation unknown
  7. 2007 High

    Reconstituted a sequential silencing pathway in which G9a methylates H3K9 to create an HP1 platform that recruits DNMT1, coupling histone and DNA methylation functionally.

    Evidence In vitro chromatin methylation, Co-IP, ChIP, and reporter assays in DNMT1-null vs. wild-type cells

    PMID:17470536

    Open questions at the time
    • In vivo ordering of methylation events at endogenous loci not fully resolved
  8. 2009 High

    Identified additional kinase control of HP1α chromatin binding: JAK2 phosphorylation of H3Y41 displaces HP1α to activate an oncogene, and an HP1α-specific CSD contact with the H3 tail mediates this.

    Evidence In vitro kinase and peptide-binding assays, ChIP, and JAK2 inhibition in leukemic cells

    PMID:19783980

    Open questions at the time
    • Scope of H3Y41ph-regulated HP1α loci beyond lmo2 not mapped
  9. 2009 Medium

    Showed HP1α nucleates a repressive ASXL1-HP1α-LSD1 complex via a PxVxL contact, coupling HP1α to H3K4 demethylation at RAR target genes.

    Evidence In vitro binding, Co-IP, mutagenesis, ChIP, and reporter assays

    PMID:19880879

    Open questions at the time
    • Structural basis of ternary complex assembly not resolved
  10. 2011 High

    Placed HP1α directly in the DNA damage response, showing p150CAF-1-dependent recruitment to breaks is required for 53BP1/RAD51 loading and homologous recombination.

    Evidence Laser microirradiation live imaging, Co-IP, RNAi, and HR/survival assays

    PMID:21464229

    Open questions at the time
    • How HP1α at undamaged heterochromatin redistributes to euchromatic breaks unclear
  11. 2012 Medium

    Dissected the structural basis of nucleosome selectivity, showing chromo, hinge, and chromoshadow domains jointly confer H3K9me3 preference, and that HP1 paralogs differentially route repair through end resection.

    Evidence In vitro nucleosome reconstitution with domain deletions/EMSA; HR/SSA repair assays with RPA loading analysis

    PMID:23142645 PMID:23287531

    Open questions at the time
    • Quantitative energetic contribution of each domain not parsed
    • Mechanism of HP1α/β vs γ divergence in resection unresolved
  12. 2013 Medium

    Defined HP1α retention determinants and repair-pathway-choice role: KAP1 scaffolds HP1α to heterochromatin and is regulated by Src-family phosphorylation, while HP1 promotes BRCA1 recruitment and HR over 53BP1/NHEJ.

    Evidence Chromatin fractionation, phosphomimetic mutants, RNAi, and focus/HR/checkpoint assays

    PMID:23589625 PMID:23645696

    Open questions at the time
    • Direct vs. indirect contributions of individual HP1 paralogs to BRCA1 loading not separated
  13. 2014 High

    Identified the regulatory phosphorylation logic of HP1α: CK2 N-terminal phosphorylation imposes H3K9me3 specificity by suppressing DNA binding, while NDR1 hinge phosphorylation targets HP1α to kinetochores for Sgo1 recruitment and mitotic fidelity.

    Evidence In vitro kinase/EMSA/nucleosome pulldowns (CK2); in vivo phosphosite mapping, RNAi, and mitotic imaging (NDR1)

    PMID:24619172 PMID:25332400

    Open questions at the time
    • Crosstalk between CK2 and NDR1 phosphorylation events not addressed
    • NDR1 study single-lab Medium confidence
  14. 2015 High

    Quantified how multivalency drives HP1α chromatin residence and showed HP1 regulates DNA-methylation-dependent alternative splicing, broadening its functional repertoire to RNA processing.

    Evidence Single-molecule TIRF on defined nucleosome arrays with controlled dimerization; genome-wide splicing analysis and targeted-methylation transgenes

    PMID:25704815 PMID:26084584

    Open questions at the time
    • Splicing-factor recruitment mechanism only partially defined
    • In vivo link between residence kinetics and gene silencing not directly tested
  15. 2016 Medium

    Established HP1 as an essential CPC component required for full Aurora B activity, with reduced HP1-CPC association causing segregation errors in cancer cells.

    Evidence Co-IP, kinase activity assays, RNAi, and chromosome segregation analysis

    PMID:26954544

    Open questions at the time
    • Structural basis of HP1-CPC contact not defined
    • Relative contributions of the three paralogs unresolved
  16. 2017 High

    Demonstrated that HP1α forms phase-separated liquid droplets driven by N-terminal phosphorylation or DNA binding, providing a biophysical model for heterochromatin compartmentalization.

    Evidence In vitro phase separation, single-molecule DNA curtains, and protein delivery into mammalian cells

    PMID:28636604

    Open questions at the time
    • In vivo extent and functional necessity of LLPS for endogenous heterochromatin not fully established
  17. 2018 High

    Resolved heterochromatin architecture at structural and single-fiber level and uncovered new HP1α complexes and mitotic functions: dimeric bridging of H3K9me3 nucleosomes, transient nucleosome stacking, CPC recruitment to G2 foci, Haspin-dependent cohesion protection, and the H3K9me3-independent ChAHP repressive complex.

    Evidence Cryo-EM and single-molecule FRET on nucleosome arrays; tethering/Co-IP for CPC and Haspin; biochemical purification, ChIP-seq/ATAC-seq, and ESC knockout for ChAHP

    PMID:29336876 PMID:29339721 PMID:29467217 PMID:29491004 PMID:29795351

    Open questions at the time
    • Interplay between LLPS and the static dimer-bridge architecture unresolved
    • ChAHP targeting determinants beyond ADNP motifs incompletely mapped
  18. 2019 Medium

    Refined the molecular basis of HP1α phase behavior and extended its repressive role to tissue pathology, identifying gel-forming phosphoserines and a CBX5/G9a axis silencing PGC1α in lung fibrosis.

    Evidence Solid-state NMR of phosphorylated HP1α; ChIP, knockdown/inhibitor, and bleomycin mouse fibrosis model

    PMID:30845353 PMID:31095524

    Open questions at the time
    • Physiological relevance of in vitro gelation not established
    • Causality of CBX5/G9a axis in human fibrosis not proven
  19. 2021 High

    Defined HP1α's mechanical and condensate functions: dimerization-dependent chromatin crosslinking stiffens nuclei and chromosomes independent of transcription, and paralog disordered regions dictate distinct condensate/DNA-compaction behaviors.

    Evidence Auxin-inducible degron with single-nucleus micromanipulation and separation-of-function mutants; single-molecule/bulk condensate imaging with paralog domain swaps

    PMID:33661100 PMID:34106828

    Open questions at the time
    • How mechanical and silencing functions are coordinated in vivo unclear
    • Telomere-protection role (tethering) remains Medium confidence
  20. 2022 Medium

    Showed HP1 tethers and stabilizes H3K9 methyltransferases/demethylases on chromatin and clarified the phosphorylation-driven conformational change underlying LLPS, integrating HP1α into maintenance of the epigenetic enzyme pool.

    Evidence Triple HP1 knockout with stability/fractionation assays and separation-of-function mutants; NMR and MD with phase-separation and peptide-ligand assays

    PMID:35166421 PMID:36537242

    Open questions at the time
    • Whether enzyme stabilization is direct or via chromatin tethering not fully separated for HP1α specifically
    • In-cell relevance of ligand-modulated LLPS untested

Open questions

Synthesis pass · forward-looking unresolved questions
  • How HP1α's multiple functions—phase separation, structural nucleosome bridging, mechanical crosslinking, mitotic kinetochore/CPC roles, and DNA repair—are coordinately deployed and switched in vivo, and how paralog-specific disordered regions partition these tasks, remains unresolved.
  • No unified in-cell model linking LLPS, static bridging, and mechanics
  • Quantitative paralog division of labor at endogenous loci undefined
  • Spatiotemporal kinase coordination (CK2/Aurora B/NDR1/JAK2) on a single HP1α pool not mapped

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0042393 histone binding 4 GO:0060090 molecular adaptor activity 4 GO:0003677 DNA binding 3 GO:0005198 structural molecule activity 2 GO:0098772 molecular function regulator activity 2 GO:0003723 RNA binding 1
Localization
GO:0000228 nuclear chromosome 4 GO:0005694 chromosome 4 GO:0005634 nucleus 2 GO:0005654 nucleoplasm 2
Pathway
R-HSA-1640170 Cell Cycle 5 R-HSA-4839726 Chromatin organization 5 R-HSA-74160 Gene expression (Transcription) 5 R-HSA-73894 DNA Repair 4 R-HSA-8953854 Metabolism of RNA 1
Partners
BARD1BRG1CAF-1 (P150)CHD4DNMT1G9AKAP1SUV39H1
Complex memberships
ASXL1-HP1α-LSD1 complexChAHP (HP1α-ADNP-CHD4)Chromosomal passenger complex (CPC)Rb-SUV39H1-HP1 repressive complex

Evidence

Reading pass · 41 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2017 Human HP1α forms phase-separated liquid droplets in vitro; unmodified HP1α is soluble, but phosphorylation of its N-terminal extension or DNA binding promotes phase separation. Known heterochromatin components (nucleosomes, DNA) preferentially partition into HP1α droplets, while TFIIB does not. An HP1α mutant incapable of phase separation forms smaller and fewer nuclear puncta when delivered into mammalian cells. In vitro phase separation assay, single-molecule DNA curtain assay, direct protein delivery into mammalian cells, fluorescence microscopy Nature High 28636604
2005 HP1α (and HP1β, HP1γ) are released from chromatin during mitotic M phase despite unchanged H3K9me3 levels. Aurora B kinase phosphorylates histone H3 serine 10 adjacent to the methyl-K9 mark, and this phosphorylation is sufficient to eject HP1 proteins from chromatin. Inhibition or depletion of Aurora B causes retention of HP1 on mitotic chromosomes, establishing a 'methyl/phospho switch' mechanism. Cell fractionation, chromatin immunoprecipitation, Aurora B inhibition/depletion, mitotic cell analysis Nature High 16222246
2001 Rb associates with SUV39H1 and HP1 in vivo via its pocket domain. Rb directs methylation of histone H3 and recruits HP1α to the cyclin E promoter; chromatin immunoprecipitation shows Rb is necessary for HP1 binding at this euchromatic promoter, indicating the SUV39H1–HP1 complex participates in Rb-mediated gene repression. Co-immunoprecipitation, chromatin immunoprecipitation, fibroblast gene expression analysis Nature High 11484059
2003 DNA methyltransferases DNMT1 and DNMT3a associate with HP1β (and HP1α) in vitro and in vivo; HP1β directly binds DNMT1 and DNMT3a, and native HP1β co-purifies with DNA methyltransferase activity, establishing a direct physical link between the H3K9 methylation machinery and DNA methylation. In vitro binding assay, co-immunoprecipitation, biochemical co-purification from nuclear extracts Nucleic Acids Research Medium 12711675
2009 Nuclear JAK2 directly phosphorylates histone H3 tyrosine 41 (H3Y41). HP1α (but not HP1β) specifically binds the H3 region containing this residue through its chromo-shadow domain; JAK2-mediated phosphorylation of H3Y41 prevents HP1α binding, linking JAK2 nuclear activity to removal of HP1α from chromatin and activation of the lmo2 oncogene. In vitro kinase assay, peptide binding/competition assay, chromatin immunoprecipitation, JAK2 inhibitor treatment in leukemic cells Nature High 19783980
2018 Cryo-EM structures of H3K9me3-containing dinucleosomes complexed with human HP1α, HP1β, and HP1γ show that a symmetric HP1 dimer bridges two H3K9me3 nucleosomes without directly contacting linker DNA, allowing nucleosome remodeling by ACF. This defines the fundamental architecture by which HP1 compacts heterochromatin. Cryo-electron microscopy with Volta phase plate, structural analysis with biochemical validation Molecular Cell High 29336876
2002 HP1α association with pericentromeric heterochromatin requires both its chromo domain (methyl-H3K9 binding) and an RNA-binding activity in the hinge region. Mutation of the hinge RNA-binding activity displaces HP1α from pericentromeric heterochromatin, indicating that heterochromatin targeting requires coordinated methyl-histone and RNA binding. Immunofluorescence, domain deletion/mutation analysis, RNA-binding assays in mammalian cells EMBO Reports Medium 12231507
2007 HP1 family members (HP1α, β, γ) mediate functional communication between G9a (H3K9 methyltransferase) and DNMT1. In vitro, G9a methylates H3K9 creating a binding platform for HP1; HP1 then recruits DNMT1, increasing DNA methylation on chromatin templates. GAL4-HP1 tethering to a reporter induces repression and DNA methylation dependent on DNMT1. In vitro chromatin methylation assay, Co-immunoprecipitation, reporter gene assay in DNMT1 wild-type vs. null cells, chromatin immunoprecipitation Genes & Development High 17470536
2010 POGZ (pogo transposable element-derived protein with zinc finger domain) binds HP1α through a zinc-finger-like motif (not the canonical PxVxL motif), competes with PxVxL-containing proteins, and destabilizes HP1α–chromatin interaction. POGZ is required for Aurora B kinase activation and for HP1α dissociation from mitotic chromosome arms. Proteomics/co-immunoprecipitation, RNAi depletion, mitotic chromosome analysis, kinase activity assay Nature Cell Biology High 20562864
2011 HP1α is rapidly and transiently recruited to laser-induced DNA damage sites in both euchromatin and heterochromatin; this recruitment depends strictly on p150CAF-1 (largest subunit of CAF-1) and its ability to interact with HP1α. HP1α depletion severely compromises recruitment of DDR proteins 53BP1 and RAD51 and causes defects in homologous recombination repair. Live-cell imaging (laser microirradiation), co-immunoprecipitation, RNAi depletion, HR repair assay, colony survival The Journal of Cell Biology High 21464229
1999 HP1α is phosphorylated throughout the cell cycle, more extensively in mitosis. In mitotic HeLa cells, HP1α (but not HP1β or HP1γ) remains associated with centromeres on spread chromosomes, whereas HP1γ distributes on chromosome arms. This isoform-specific mitotic retention and phosphorylation indicates paralog-specific functions in heterochromatin. Isoform-specific immunostaining, biochemical fractionation across cell cycle stages, spread chromosome immunostaining Chromosoma Medium 10460410
2004 In mammalian cells, FRAP and FCS analyses reveal that most HP1 molecules (50–80%) are highly mobile, ~20–40% are in slow oligomeric complexes, and 5–7% are very slow within constitutive heterochromatin. The proportion of very slow HP1α increases with chromatin condensation and is isoform-specific during mitosis, indicating HP1α has a unique, stable heterochromatin-binding pool. Fluorescence correlation spectroscopy (FCS), fluorescence recovery after photobleaching (FRAP), live-cell imaging Molecular Biology of the Cell Medium 15064352
2014 CK2 (casein kinase II) is the primary kinase phosphorylating the N-terminus of human HP1α. Unphosphorylated HP1α binds H3K9-methylated and unmethylated nucleosomes with comparable affinity, whereas CK2-phosphorylated HP1α shows high specificity for H3K9me3 nucleosomes by suppressing intrinsic DNA-binding activity. This effect is conserved in fly HP1a and S. pombe Swi6. In vitro phosphorylation assay, pull-down with reconstituted nucleosomes, electrophoretic mobility shift assay (EMSA) Nucleic Acids Research High 25332400
2015 HP1α residence time on chromatin depends on the local density of H3K9me3; HP1α dimerization prolongs chromatin retention and accelerates association rate through increased avidity and strengthened nonspecific chromatin interactions, enabling efficient competition for binding sites. Single-molecule total internal reflection fluorescence microscopy (smTIRFM) with chemically defined nucleosome arrays and controlled HP1α dimerization Nature Communications High 26084584
2018 Single-molecule FRET shows that HP1α engages methylated H3 tails and transiently stabilizes stacked nucleosomes in chromatin fibers, promoting compaction while maintaining dynamic fluctuations on the timescale of HP1α residence times. Single-molecule FRET, nucleosome array reconstitution, kinetic analysis Nature Communications Medium 29339721
2021 HP1α (CBX5) acts as a chromatin crosslinker that imparts mechanical stiffness to nuclei and mitotic chromosomes. Rapid auxin-inducible degradation of HP1α decreases chromatin stiffness and impairs nuclear morphology without altering transcription, local compaction, or H3K9 methylation. Dimerization-deficient HP1αI165E fails to rescue stiffness, indicating chromatin crosslinking via HP1α dimerization is the critical mechanical mechanism. Auxin-inducible degron system, single-nucleus micromanipulation, polymer simulations, dimerization-deficient mutant analysis eLife High 34106828
2021 Within phase-separated HP1α–DNA condensates, HP1α behaves as a dynamic liquid while compacted DNA molecules are constrained in local territories. HP1β dissolves HP1α condensates. Differences in phase-separation and DNA compaction properties among HP1 paralogs arise from their respective disordered regions. Bulk and single-molecule fluorescence microscopy, DNA compaction assays, phase separation assay, paralog domain-swap analysis eLife High 33661100
2002 HP1α, but not HP1β or HP1γ, selectively forms a complex with BRG1 chromatin-remodeling factor in HeLa cells. The interaction maps to residues 106–180 of HP1α's chromoshadow domain, and three specific residues (I113, A114, C133) are essential for selective binding and for HP1α silencing activity. Co-immunoprecipitation, in vitro direct binding assay, site-directed mutagenesis The EMBO Journal Medium 12411497
2002 HP1α and HP1γ (but not HP1β) associate with the TFIID component hTAFII130 via its pentapeptide HP1-binding motif. Mutation of the HP1 box abolishes interaction. Gal4-HP1α/γ proteins interfere with hTAFII130-mediated transcriptional activation, suggesting HP1α/γ repress transcription by interacting with TFIID. Yeast two-hybrid, GST pulldown from HeLa nuclear extracts, co-immunoprecipitation, reporter gene assay, site-directed mutagenesis Proceedings of the National Academy of Sciences Medium 11959914
2014 NDR1 kinase phosphorylates HP1α within its hinge domain preferentially at G2/M phase. Hinge-phosphorylated HP1α specifically localizes to kinetochores during early mitosis and is required for mitotic progression and for Sgo1 binding to mitotic centromeres. Cells lacking NDR kinase show loss of mitosis-specific HP1α hinge phosphorylation and prometaphase arrest. In vivo phosphorylation mapping, kinase assay, immunofluorescence, RNAi knockdown, cell cycle analysis Nature Communications Medium 24619172
2016 HP1 (all three isoforms in mammals) is an essential component of the chromosomal passenger complex (CPC) required for full Aurora B kinase activity. HP1 binding to the CPC becomes especially critical when Aurora B phosphorylates kinetochore targets to eliminate erroneous microtubule attachments. Reduced HP1–CPC association in cancer cells impairs Aurora B activity and causes chromosome segregation errors. Co-immunoprecipitation, kinase activity assay, RNAi, chromosome segregation analysis, cancer cell line analysis Developmental Cell Medium 26954544
2018 HP1α and HP1γ cooperate to recruit the chromosomal passenger complex (CPC) to active heterochromatic foci in G2 in a CDK1-independent manner. Tethering HP1α near centromeres strongly recruits the CPC, activates Aurora B, and destabilizes kinetochore-microtubule interactions. During mitotic exit, tethered HP1 traps active CPC at centromeres throughout the subsequent cell cycle. HP1-CENP-B tethering, live-cell imaging with Fab fragment tracking, co-immunoprecipitation, Aurora B activity readout (H3S10ph) The EMBO Journal Medium 29467217
2018 HP1α directly interacts with CHD4 and ADNP to form the stable ChAHP complex. ChAHP-mediated repression acts in a locally restricted manner by establishing inaccessible chromatin without requiring H3K9me3, distinct from canonical HP1-mediated heterochromatin. ADNP recognizes DNA motifs specifying ChAHP binding to euchromatin. Biochemical complex purification, co-immunoprecipitation, ChIP-seq, ATAC-seq, genetic ablation in mouse embryonic stem cells Nature High 29795351
2018 HP1α double knockout (with HP1γ) causes defective mitotic progression and weakened centromeric cohesion. HP1α chromoshadow domain (CSD) is required to protect sister-chromatid cohesion, and centromeric targeting of the CSD alone rescues cohesion defects. HP1α CSD directly binds the N-terminal region of Haspin kinase, facilitating its centromeric localization and thereby protecting cohesin from Wapl-mediated release. Double knockout cell lines, Co-immunoprecipitation, centromere localization assay, cohesion assay, domain-mapping pulldown EMBO Reports Medium 29491004
2009 ASXL1 interacts with the chromoshadow domain of HP1α via a consensus PxVxL HP1-binding box. HP1α is required for ASXL1-mediated transcriptional repression of RAR target genes. HP1α also promotes ASXL1 interaction with the histone demethylase LSD1, forming a ternary ASXL1–HP1α–LSD1 complex that removes H3K4 methylation to repress RAR-dependent transcription. In vitro binding assay, co-immunoprecipitation, reporter gene assay, ChIP, HP1α knockdown, site-directed mutagenesis The Journal of Biological Chemistry Medium 19880879
2008 HP1α (but not HP1β) directly interacts with MyoD in myoblasts; this interaction is direct (shown with recombinant proteins in vitro). HP1α and HP1β (not HP1γ) inhibit MyoD transcriptional activity. HP1 proteins are preferentially recruited to MyoD target gene promoters in proliferating myoblasts, and modulation of HP1 levels impairs MyoD target gene expression and muscle terminal differentiation. Co-immunoprecipitation, in vitro binding with recombinant proteins, reporter gene assay, chromatin immunoprecipitation, RNAi modulation The Journal of Biological Chemistry Medium 18599480
2015 BARD1's BRCT domain contains a conserved HP1-binding motif that directly interacts with the chromoshadow domain of HP1 in vitro. In response to DNA damage, BARD1 interacts with H3K9me2 in an ATM-dependent manner primarily via HP1γ. Mutations in the HP1-binding motif, or triple HP1 depletion, disrupt BRCA1/BARD1/CtIP retention at DSBs and allow ectopic RIF1 accumulation, impairing homologous recombination. In vitro direct binding, co-immunoprecipitation, site-directed mutagenesis, laser microirradiation, focus assay, HR assay Cancer Research Medium 25634209
2019 G9a (EHMT2) and HP1α (CBX5) cooperate to silence PPARGC1A (PGC1α) in lung fibroblasts via H3K9 methylation-dependent epigenetic repression. Both TGFβ and increased matrix stiffness inhibit PGC1α through the CBX5/G9a pathway. Inhibition of the CBX5/G9a pathway elevates PGC1α and reduces collagen accumulation in bleomycin-injured lungs. ChIP, RNAi/inhibitor knockdown, reporter assays, bleomycin mouse model of fibrosis JCI Insight Medium 31095524
2012 All three human HP1 paralogs differentially modulate homology-directed repair (HDR): HP1α and HP1β stimulate HR and single-strand annealing, while HP1γ has an inhibitory role. The stimulatory role of HP1α and β in HDR is linked to promotion of DNA-end resection through RPA loading and phosphorylation at damage sites. HR/SSA repair assays, RPA loading/phosphorylation analysis at DSBs, RNAi depletion, laser microirradiation Cell Cycle Medium 23287531
2015 HP1 regulates DNA methylation-dependent alternative splicing. HP1 silences or enhances exon recognition in a position-dependent manner, and recruits splicing factors to methylated genomic regions to regulate splicing, as demonstrated by site-specific targeting of methylated/unmethylated transgenes. Genome-wide splicing analysis in methylation-deficient ES cells, site-specific gene methylation targeting, ChIP, splicing factor recruitment assay Cell Reports Medium 25704815
2022 HP1 (all three paralogs) interacts with H3K9 methyltransferases (Suv39h1, Suv39h2, Setdb1, G9a/GLP) and demethylases (Jmjd1a, Jmjd1b) and maintains their protein stability. In HP1-triple-knockout mouse ES cells, these enzymes decrease at the protein level and are released from chromatin. HP1 mutants that cannot bind H3K9me2/3 or dimerize cannot stabilize these enzymes, indicating tethering to chromatin via HP1 is critical. Triple HP1 knockout cell lines, protein stability assays, chromatin fractionation, co-immunoprecipitation, HP1 mutant analysis EMBO Reports High 35166421
2012 HP1α nucleosome binding involves not only its chromo domain (recognizing H3K9 trimethylation) but also contributions from the hinge region (weak DNA binding) and the chromoshadow domain (suppressing non-specific DNA binding), which together confer selectivity for H3K9me3-containing nucleosomes over unmodified nucleosomes. In vitro nucleosome reconstitution, pull-down binding assay with domain deletions, EMSA Journal of Molecular Biology Medium 23142645
2006 HP1α interacts with replication origin recognition complex proteins ORC1, ORC2, and CDC6 by yeast two-hybrid and co-immunoprecipitation; HP1α co-localizes with these proteins in heterochromatin. RNAi depletion of HP1α leads to slow cell proliferation, aberrant cell cycle progression, and multinucleated cells with disorganized microtubules, suggesting a role in mitosis and cytokinesis. Yeast two-hybrid, co-immunoprecipitation, immunofluorescence colocalization, RNAi knockdown, cell cycle analysis Experimental Cell Research Low 16950245
2017 SALL4 promotes open chromatin by recruiting the ubiquitin E3 ligase CUL4B to HP1α, leading to HP1α destabilization. HP1α upregulation in cancer cells suppresses open chromatin, glycolysis, and Glut1 expression. Impaired DDR in SALL4-deficient cells is rescued by restored Glut1 expression, positioning HP1α as a mediator of the SALL4–Glut1–DDR axis. Co-immunoprecipitation, chromatin accessibility assay, gene expression analysis, rescue experiments Oncogene Low 28759035
2013 KAP1 tyrosine phosphorylation at Tyr-449/458/517 by Src family kinases (Src, Lyn, Abl, Brk) decreases KAP1 association with heterochromatin and, because KAP1 bridges HP1α to heterochromatin, thereby decreases HP1α association with heterochromatin. KAP1 knockdown impairs HP1α heterochromatin association, placing KAP1 as an essential scaffold for HP1α retention. Immunostaining, chromatin fractionation, kinase activity-dependent manipulation, siRNA knockdown, phosphomimetic mutation analysis The Journal of Biological Chemistry Medium 23645696
2019 Solid-state NMR spectroscopy of phosphorylated HP1α during liquid-to-gel transition identifies specific serine residues that uniquely contribute to gel formation. Chromatin addition disturbs the gelation process while preserving conformational dynamics within individual HP1α molecules. Solid-state NMR spectroscopy, in vitro phase separation/gelation assay, chromatin addition experiment Angewandte Chemie Medium 30845353
2022 Phosphorylation of HP1α N-terminal extension drives conformational change from a compacted to an extended HP1α dimer, enabling intermolecular hinge-NTE interactions that promote phase separation. Positively charged HP1α peptide ligands enhance phosphorylation-driven LLPS; negatively charged or neutral peptides disrupt it. In DNA-driven LLPS, electrostatic interactions with the hinge region are similarly modulated by ligands. NMR spectroscopy, molecular dynamics simulation, in vitro phase separation assay, peptide ligand competition assay Nucleic Acids Research Medium 36537242
2007 HP1α levels increase progressively during neuronal terminal differentiation. HP1α, but not HP1β or HP1γ, enforces permanent silencing of E2F-target cell-cycle genes in mature neurons, taking over from HP1γ at E2F sites. Specific inhibition of HP1α drives neuronal progenitors toward death or cell cycle re-entry and prevents MAP2 expression, demonstrating a unique isoform-specific silencing function during neuronal differentiation. Overexpression and isoform-specific knockdown in neuronal cells, ChIP at E2F sites, reporter assay, in vivo cerebellar analysis The EMBO Journal Medium 17627279
2021 RBMX and RBMXL1 RNA-binding proteins directly bind CBX5 (HP1α) mRNAs and control nascent transcription of the CBX5 locus. Forced CBX5 expression rescues the cell growth and apoptosis defects caused by RBMX/L1 depletion in AML cells, placing CBX5 as a key downstream effector of RBMX/L1 in maintaining chromatin state in leukemia. mRNA binding (CLIP), nascent transcription assay, RNAi depletion, CBX5 forced expression rescue, chromatin accessibility assay Nature Cancer Medium 34458856
2018 Local enrichment of HP1α at cancer cell telomeres (by molecular tethering) increases H3K9me3 deposition, attenuates telomere extension by telomerase, reduces damage-induced foci, and increases telomere structural irregularity. The chromoshadow domain I165A mutant abrogates these effects, implicating HP1α-ligand interactions in mediating telomere protection. Molecular tethering, ChIP, telomere length assay, STORM super-resolution imaging, CSD mutant analysis Nature Communications Medium 30181605
2013 HP1 depletion reduces BRCA1 recruitment to DSBs and impairs BRCA1-mediated functions: homologous recombination and G2/M checkpoint arrest. Conversely, HP1 depletion does not affect NHEJ; instead it elevated 53BP1 recruitment, suggesting HP1 influences DNA repair pathway choice. RNAi depletion of HP1 isoforms, γH2AX focus assay, HR reporter assay, BRCA1/53BP1 focus quantification, G2/M checkpoint analysis Nucleic Acids Research Medium 23589625

Source papers

Stage 0 corpus · 100 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2017 Liquid droplet formation by HP1α suggests a role for phase separation in heterochromatin. Nature 1325 28636604
2005 Regulation of HP1-chromatin binding by histone H3 methylation and phosphorylation. Nature 760 16222246
2001 Rb targets histone H3 methylation and HP1 to promoters. Nature 720 11484059
2003 The DNA methyltransferases associate with HP1 and the SUV39H1 histone methyltransferase. Nucleic acids research 571 12711675
2009 JAK2 phosphorylates histone H3Y41 and excludes HP1alpha from chromatin. Nature 482 19783980
2019 HP1 reshapes nucleosome core to promote phase separation of heterochromatin. Nature 385 31618757
2000 The HP1 protein family: getting a grip on chromatin. Current opinion in genetics & development 384 10753776
2008 HP1-beta mobilization promotes chromatin changes that initiate the DNA damage response. Nature 341 18438399
1999 Localization and phosphorylation of HP1 proteins during the cell cycle in mammalian cells. Chromosoma 288 10460410
2002 Coordinated methyl and RNA binding is required for heterochromatin localization of mammalian HP1alpha. EMBO reports 273 12231507
2007 Functional cooperation between HP1 and DNMT1 mediates gene silencing. Genes & development 260 17470536
2018 Structural Basis of Heterochromatin Formation by Human HP1. Molecular cell 218 29336876
2010 Human POGZ modulates dissociation of HP1alpha from mitotic chromosome arms through Aurora B activation. Nature cell biology 218 20562864
2018 GDV1 induces sexual commitment of malaria parasites by antagonizing HP1-dependent gene silencing. Science (New York, N.Y.) 190 29590075
2008 HP1 proteins form distinct complexes and mediate heterochromatic gene silencing by nonoverlapping mechanisms. Molecular cell 189 19111658
2021 HP1 proteins compact DNA into mechanically and positionally stable phase separated domains. eLife 174 33661100
2004 HP1 is essential for DNA methylation in neurospora. Molecular cell 173 14967149
2014 Mechanisms of functional promiscuity by HP1 proteins. Trends in cell biology 168 24618358
2015 HP1 is involved in regulating the global impact of DNA methylation on alternative splicing. Cell reports 167 25704815
2011 HP1alpha recruitment to DNA damage by p150CAF-1 promotes homologous recombination repair. The Journal of cell biology 159 21464229
2018 Activity-dependent neuroprotective protein recruits HP1 and CHD4 to control lineage-specifying genes. Nature 156 29795351
2004 High- and low-mobility populations of HP1 in heterochromatin of mammalian cells. Molecular biology of the cell 142 15064352
2008 G9a and HP1 couple histone and DNA methylation to TNFalpha transcription silencing during endotoxin tolerance. The Journal of biological chemistry 141 18809684
2010 HP1: heterochromatin binding proteins working the genome. Epigenetics 124 20421743
2021 HP1α is a chromatin crosslinker that controls nuclear and mitotic chromosome mechanics. eLife 119 34106828
2008 The heterochromatin protein 1 (HP1) family: put away a bias toward HP1. Molecules and cells 119 18664736
2008 HP1: a functionally multifaceted protein. Current opinion in genetics & development 116 18329871
2018 Single-molecule FRET reveals multiscale chromatin dynamics modulated by HP1α. Nature communications 112 29339721
2008 Linking Heterochromatin Protein 1 (HP1) to cancer progression. Mutation research 109 18926834
2021 HP1 drives de novo 3D genome reorganization in early Drosophila embryos. Nature 108 33854237
2012 HP1(Swi6) mediates the recognition and destruction of heterochromatic RNA transcripts. Molecular cell 104 22683269
2009 The emerging role of HP1 in the DNA damage response. Molecular and cellular biology 102 19805510
2018 Plant HP1 protein ADCP1 links multivalent H3K9 methylation readout to heterochromatin formation. Cell research 100 30425322
2004 Mechanisms of HP1-mediated gene silencing in Drosophila. Development (Cambridge, England) 96 15215206
2015 Multivalency governs HP1α association dynamics with the silent chromatin state. Nature communications 87 26084584
2013 HP1 promotes tumor suppressor BRCA1 functions during the DNA damage response. Nucleic acids research 86 23589625
2005 Genome-wide HP1 binding in Drosophila: developmental plasticity and genomic targeting signals. Genome research 85 16109969
2019 CBX5/G9a/H3K9me-mediated gene repression is essential to fibroblast activation during lung fibrosis. JCI insight 82 31095524
2015 Interaction of BARD1 and HP1 Is Required for BRCA1 Retention at Sites of DNA Damage. Cancer research 81 25634209
2015 The nuclear oncogene SET controls DNA repair by KAP1 and HP1 retention to chromatin. Cell reports 79 25818296
2009 ASXL1 represses retinoic acid receptor-mediated transcription through associating with HP1 and LSD1. The Journal of biological chemistry 77 19880879
2002 Selective interaction between the chromatin-remodeling factor BRG1 and the heterochromatin-associated protein HP1alpha. The EMBO journal 76 12411497
2005 HP1 modulates the transcription of cell-cycle regulators in Drosophila melanogaster. Nucleic acids research 74 15905474
2012 Proteogenomic characterization and mapping of nucleosomes decoded by Brd and HP1 proteins. Genome biology 73 22897906
2007 Plasticity of HP1 proteins in mammalian cells. Journal of cell science 71 17855382
2000 Phosphorylation site mutations in heterochromatin protein 1 (HP1) reduce or eliminate silencing activity. The Journal of biological chemistry 71 11121421
2014 N-terminal phosphorylation of HP1α increases its nucleosome-binding specificity. Nucleic acids research 70 25332400
2016 HP1-Assisted Aurora B Kinase Activity Prevents Chromosome Segregation Errors. Developmental cell 63 26954544
2009 Mobilization and recruitment of HP1: a bimodal response to DNA breakage. Cell cycle (Georgetown, Tex.) 62 19657222
2022 Molecular interactions underlying the phase separation of HP1α: role of phosphorylation, ligand and nucleic acid binding. Nucleic acids research 61 36537242
2002 Isoform-specific interaction of HP1 with human TAFII130. Proceedings of the National Academy of Sciences of the United States of America 61 11959914
2010 HP1 recruitment in the absence of argonaute proteins in Drosophila. PLoS genetics 60 20300658
2019 Heterochromatin Protein HP1α Gelation Dynamics Revealed by Solid-State NMR Spectroscopy. Angewandte Chemie (International ed. in English) 59 30845353
2002 HP1: facts, open questions, and speculation. Journal of structural biology 58 12490149
2020 Heterochromatin protein 1 (HP1): interactions with itself and chromatin components. Biophysical reviews 55 32144738
2018 HP1 links centromeric heterochromatin to centromere cohesion in mammals. EMBO reports 50 29491004
2007 POF and HP1 bind expressed exons, suggesting a balancing mechanism for gene regulation. PLoS genetics 50 18020713
2012 Network biology of tumor stem-like cells identified a regulatory role of CBX5 in lung cancer. Scientific reports 49 22900142
1992 Cloning and expression of Drosophila HP1 homologs from a mealybug, Planococcus citri. Journal of cell science 49 1629256
2022 HP1 maintains protein stability of H3K9 methyltransferases and demethylases. EMBO reports 48 35166421
2012 Differential contribution of HP1 proteins to DNA end resection and homology-directed repair. Cell cycle (Georgetown, Tex.) 47 23287531
2022 KCNQ1OT1 promotes genome-wide transposon repression by guiding RNA-DNA triplexes and HP1 binding. Nature cell biology 46 36266489
2007 HP1alpha guides neuronal fate by timing E2F-targeted genes silencing during terminal differentiation. The EMBO journal 46 17627279
2023 HP1-driven phase separation recapitulates the thermodynamics and kinetics of heterochromatin condensate formation. Proceedings of the National Academy of Sciences of the United States of America 45 37549295
2006 Interaction between HP1alpha and replication proteins in mammalian cells. Experimental cell research 42 16950245
2003 HP1 complexes and heterochromatin assembly. Current topics in microbiology and immunology 42 12596904
2013 H3K9/HP1 and Polycomb: two key epigenetic silencing pathways for gene regulation and embryo development. Current topics in developmental biology 41 23587244
2012 Hinge and chromoshadow of HP1α participate in recognition of K9 methylated histone H3 in nucleosomes. Journal of molecular biology 41 23142645
2013 Phosphorylation of KRAB-associated protein 1 (KAP1) at Tyr-449, Tyr-458, and Tyr-517 by nuclear tyrosine kinases inhibits the association of KAP1 and heterochromatin protein 1α (HP1α) with heterochromatin. The Journal of biological chemistry 39 23645696
2007 Loss of RB compromises specific heterochromatin modifications and modulates HP1alpha dynamics. Journal of cellular physiology 38 17245754
2022 Functions of HP1 proteins in transcriptional regulation. Epigenetics & chromatin 36 35526078
2014 Dynamic phosphorylation of HP1α regulates mitotic progression in human cells. Nature communications 34 24619172
2004 Conserved properties of HP1(Hsalpha). Gene 34 15225874
2001 Ectopic HP1 promotes chromosome loops and variegated silencing in Drosophila. The EMBO journal 33 11179225
2018 HP1α targets the chromosomal passenger complex for activation at heterochromatin before mitotic entry. The EMBO journal 32 29467217
2017 SALL4 promotes glycolysis and chromatin remodeling via modulating HP1α-Glut1 pathway. Oncogene 32 28759035
2014 The Caenorhabditis elegans HP1 family protein HPL-2 maintains ER homeostasis through the UPR and hormesis. Proceedings of the National Academy of Sciences of the United States of America 32 24715729
2007 Differentiation-specific association of HP1alpha and HP1beta with chromocentres is correlated with clustering of TIF1beta at these sites. Histochemistry and cell biology 32 17205308
2017 Association of serum levels of antibodies against MMP1, CBX1, and CBX5 with transient ischemic attack and cerebral infarction. Oncotarget 31 29464021
2015 Phosphorylation of an HP1-like Protein Regulates Heterochromatin Body Assembly for DNA Elimination. Developmental cell 31 26688337
2003 HP1beta and HP1gamma, but not HP1alpha, decorate the entire XY body during human male meiosis. Chromosome research : an international journal on the molecular, supramolecular and evolutionary aspects of chromosome biology 31 12675308
2015 Beyond the histone tale: HP1α deregulation in breast cancer epigenetics. Cancer biology & therapy 29 25588111
2012 Ers1 links HP1 to RNAi. Proceedings of the National Academy of Sciences of the United States of America 29 22733737
2024 Interplay between charge distribution and DNA in shaping HP1 paralog phase separation and localization. eLife 28 38592759
2021 LncRNA SNHG11 aggravates cell proliferation and migration in triple-negative breast cancer via sponging miR-2355-5p and targeting CBX5. Experimental and therapeutic medicine 28 34257707
2021 Transcriptional control of CBX5 by the RNA binding proteins RBMX and RBMXL1 maintains chromatin state in myeloid leukemia. Nature cancer 28 34458856
2008 Differential cooperation between heterochromatin protein HP1 isoforms and MyoD in myoblasts. The Journal of biological chemistry 28 18599480
2003 HP1/ORC complex and heterochromatin assembly. Genetica 28 12723692
2019 Transcriptional gene silencing requires dedicated interaction between HP1 protein Chp2 and chromatin remodeler Mit1. Genes & development 27 30808655
2018 MacroH2A1.2 inhibits prostate cancer-induced osteoclastogenesis through cooperation with HP1α and H1.2. Oncogene 27 29925860
2018 Local enrichment of HP1alpha at telomeres alters their structure and regulation of telomere protection. Nature communications 26 30181605
2021 POGZ promotes homology-directed DNA repair in an HP1-dependent manner. EMBO reports 24 34758190
2019 Heterochromatin protein 1 (HP1) is intrinsically required for post-transcriptional regulation of Drosophila Germline Stem Cell (GSC) maintenance. Scientific reports 24 30867469
2018 Identification of miR-758-3p as Potential Modulator of CBX5 Expression in Gastric Cancer. Technology in cancer research & treatment 24 30486755
2020 How HP1 Post-Translational Modifications Regulate Heterochromatin Formation and Maintenance. Cells 23 32545538
2020 Long non-conding RNA LOXL1-AS1 sponges miR-589-5p to up-regulate CBX5 expression in renal cell carcinoma. Bioscience reports 23 33185692
2013 Pericentric heterochromatin generated by HP1 protein interaction-defective histone methyltransferase Suv39h1. The Journal of biological chemistry 23 23836914
2024 The condensation of HP1α/Swi6 imparts nuclear stiffness. Cell reports 22 38900638
2017 BRD4 facilitates DNA damage response and represses CBX5/Heterochromatin protein 1 (HP1). Oncotarget 22 28881656
2000 A GAL4-HP1 fusion protein targeted near heterochromatin promotes gene silencing. Chromosoma 22 11151674

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