| 2000 |
UBN1 (ubinuclein) is a nuclear protein that interacts with the basic domains of EBV transcription factor EB1 and cellular c-Jun, competing with their binding to the AP1 consensus site. The NH2 terminus is essential for nuclear localization, while the central domain mediates interaction with EB1. |
Yeast two-hybrid, co-immunoprecipitation, overexpression of tagged constructs in keratinocytes |
The Journal of cell biology |
Medium |
10725330
|
| 2008 |
UBN1 is the human ortholog of yeast Hpc2p. Its Hpc2-related domain (HRD) directly interacts with the N-terminal WD repeats of HIRA. UBN1 binds to proliferation-promoting genes repressed during senescence, associates with H3K9 histone methyltransferase activity, and is indispensable for formation of senescence-associated heterochromatin foci (SAHF). |
Bioinformatic ortholog identification, pulldown assays, co-immunoprecipitation, ChIP, RNAi knockdown with SAHF phenotype readout |
Molecular and cellular biology |
High |
19029251
|
| 2011 |
UBN1 is a core subunit of the quaternary HIRA/UBN1/CABIN1/ASF1a (HUCA) complex. HIRA acts as a scaffold to bring together UBN1, ASF1a, and CABIN1. The intact HUCA complex preferentially deposits histone variant H3.3 into chromatin in a DNA replication-independent manner and contributes to heterochromatinization in senescent cells. |
Co-immunoprecipitation at ectopic and endogenous levels, reconstitution of quaternary complex from recombinant proteins, mutational analysis |
Molecular and cellular biology |
High |
21807893
|
| 2012 |
A region within residues 41–77 of UBN1, termed the NHRD (N-terminal Hpc2-related domain), is essential for interaction with the HIRA WD repeat domain, forming a tight 1:1 complex with nanomolar affinity. The previously identified HRD (residues 120–175) is dispensable for this interaction. Key residues in the NHRD are required for HUCA complex stability in vitro and in vivo and for chromatin organization in primary human cells. |
Biochemical/mutational analysis, analytical ultracentrifugation, in vitro binding assays, in vivo functional complementation |
Biochemistry |
High |
22401310
|
| 2012 |
UBN1 interacts with tight junction protein ZO-1 via UBN1's N-terminal region (residues 39–223) and ZO-1's PDZ2 domain. UBN1 also interacts with cingulin, LYRIC, and RACK-1, suggesting a scaffold function influencing protein subcellular localization at cell–cell contacts. |
Fluorescent protein-complementation assay (PCA), in vitro pull-down, co-immunoprecipitation, confocal microscopy, mass spectrometry |
Experimental cell research |
Medium |
22245583
|
| 2013 |
UBN1 colocalizes with HIRA, ASF1a, and histone H3.3 predominantly at active promoters and active/poised enhancers genome-wide. HIRA is required for deposition of H3.3 at these binding sites. Physical interactions between the HIRA complex (including UBN1) and transcription factors, a chromatin insulator, and an ATP-dependent chromatin-remodeling complex were identified. |
ChIP-seq, gene expression analysis, co-immunoprecipitation |
Cell reports |
High |
23602572
|
| 2016 |
OGT (O-GlcNAc transferase) interacts with UBN1 and O-GlcNAcylates HIRA at S231, promoting formation of the HIRA–H3.3 complex and H3.3 nucleosome assembly. Depletion of OGT or expression of HIRA S231A mutant compromises H3.3 nucleosome assembly and delays premature cellular senescence. |
Co-immunoprecipitation, O-GlcNAcylation assay, site-directed mutagenesis (HIRA S231A), nucleosome assembly assay, RNAi knockdown with senescence phenotype readout |
Proceedings of the National Academy of Sciences of the United States of America |
High |
27217568
|
| 2018 |
The UBN1 HRD specifically binds to H3.3/H4 over H3.1/H4, providing selectivity for the histone variant. The UBN1 middle domain has dimer formation activity and binds H3/H4 without discriminating between H3.1 and H3.3. A DNA-binding domain located between the HRD and middle domain binds DNA through electrostatic contacts involving conserved lysine residues. These activities suggest UBN1 associates with DNA and dimerizes to mediate (H3.3/H4)2 heterotetramer formation prior to chromatin deposition. |
In vitro binding assays, mutagenesis of conserved lysine residues, biochemical characterization of domains |
The Journal of biological chemistry |
High |
31040182
|
| 2018 |
Ala87 and Gly90 residues of H3.3 are required and sufficient for specific recognition and direct binding by UBN1. The HIRA subunit enhances UBN1 binding affinity toward H3.3, whereas CABIN1 does not. UBN1 (and UBN2) FID/AAA histone chaperone activity mutations cause defects in H3.3 deposition at promoters of developmental genes and impair neural differentiation of mouse ES cells. |
In vitro binding assays, site-directed mutagenesis of H3.3 residues, ChIP-seq, FID/AAA mutant functional analysis in mES cell differentiation |
BMC biology |
High |
30285846
|
| 2018 |
HIRA forms a stable homotrimer that binds two subunits of CABIN1 in vitro. A HIRA mutant defective in homotrimer formation interacts less efficiently with CABIN1, is not enriched at DNA damage sites upon UV irradiation, and cannot rescue new H3.3 deposition in HIRA knockout cells. UBN1 is a subunit of this trimeric complex. |
Biochemical analysis, X-ray crystallography, mutagenesis of HIRA trimerization interface, functional rescue assay in HIRA KO cells, UV damage localization |
Nature communications |
High |
30082790
|
| 2010 |
UBN1 overexpression represses the EBV productive cycle in epithelial cells, whereas UBN1 knockdown increases virus production. UBN1 blocks EB1-DNA interaction as shown by ChIP. In non-dividing differentiated epithelial cells, UBN1 is relocalized/sequestered to tight junctions, allowing EB1 to activate the productive cycle in the nucleus. |
Overexpression, shRNA knockdown, ChIP, confocal microscopy for subcellular localization |
Journal of virology |
Medium |
21084479
|
| 2020 |
De novo H3.3 deposition during transcription is totally dependent on HIRA trimerization and on UBN1, while ASF1 interaction with HIRA can be bypassed for this pathway. In contrast, recycling of old H3.3 requires HIRA but proceeds independently of UBN1 or HIRA trimerization and shows absolute dependency on ASF1-HIRA interaction. Thus UBN1 is specifically required for the de novo deposition pathway but not the recycling pathway. |
SNAP-tag pulse-chase to distinguish new and old histones, HIRA/UBN1 mutant analysis, fluorescence imaging in human cells |
Nature structural & molecular biology |
High |
32895554
|
| 2020 |
In C. elegans, PQN-80 (the UBN1 ortholog) loss of function causes late-onset pleiotropic defects similar to hira-1 mutants including mitochondrial stress, and these defects can be maternally rescued by maternally derived complex components. |
Genetic loss-of-function screen, phenotypic analysis, maternal rescue experiments |
Current biology : CB |
Medium |
32470364
|
| 2022 |
Loss of Ubn1 function in mouse oocytes (as part of the Hira/Cabin1/Ubn1 complex) causes early embryogenesis failure. Transcriptome analyses show aberrant transcriptional silencing in mutant oocytes, with reduced H3K4me3 and H3K9me3 marks and impaired chromatin accessibility. |
Genetic knockout, transcriptome analysis, nascent RNA analysis, histone mark ChIP, chromatin accessibility assay (ATAC) |
Development (Cambridge, England) |
Medium |
35112132
|
| 2023 |
UBN1 directly interacts with AID (activation-induced cytidine deaminase) in B cells. Co-immunoprecipitation, pull-down, co-localization by double immunofluorescence, and proximity ligation assay all confirm this interaction. |
Co-immunoprecipitation, pull-down, double immunofluorescence, proximity ligation assay, molecular docking |
Scientific reports |
Medium |
37949972
|
| 2024 |
The HIRA-UBN1/UBN2 complex deposits new H3.3 at telomeres to prevent accumulation of nucleosome-free ssDNA, TERRA R-loop buildup, and transcription-replication conflicts in ATRX-DAXX-deficient ALT cancer cells. HIRA-mediated H3.3 incorporation links productive ALT to phosphorylation of H3.3 serine 31 by Chk1. |
ATAC-seq, CUT&RUN, HIRA/UBN1/UBN2 depletion with defined molecular phenotypes, R-loop detection |
Cell reports |
Medium |
39509271
|
| 2024 |
ASF1a delivers H3.3/H4 dimers to the HIRA complex; H3.3/H4 tetramerization drives association of two HIRA/UBN1 complexes; and affinity of histones for DNA drives release of ASF1a and subsequent histone deposition. Biochemical and biophysical data support this stepwise mechanism for HIRA-complex-mediated H3.3/H4 deposition. |
Biochemical reconstitution, biophysical binding assays |
The Journal of biological chemistry |
Medium |
39059488
|
| 2025 |
Ubn1 single mutant mice are viable and fertile, while combined Ubn1/Ubn2 double mutants show complete embryonic lethality. Mechanistically, Ubn1 mutation in mouse ES cells impairs initiation of X chromosome inactivation: Xist-mediated establishment of H3K27me3 over X-linked genes is impaired, while Xist-dependent deacetylation of H3K27 remains largely unaffected. |
Genetic knockout (single and double mutant), mouse phenotypic analysis, ChIP for H3K27me3/ac in ES cells during Xist induction |
PLoS genetics |
High |
40455860
|
| 2025 |
Sp100A isoform is required for localization of the HIRA complex (including UBN1 and ASF1a) to PML nuclear bodies in human keratinocytes. In Sp100 knockout cells, HIRA/UBN1/ASF1a fail to localize to PML-NBs even after interferon stimulation; exogenous Sp100A rescues this, with the SUMO interacting motif (SIM) playing an important role. |
CRISPR-Cas9 Sp100 knockout, immunofluorescence localization, exogenous isoform expression rescue, interferon stimulation |
bioRxivpreprint |
Medium |
40568077
|