Affinage

HMGXB4

HMG domain-containing protein 4 · UniProt Q9UGU5

Length
601 aa
Mass
65.7 kDa
Annotated
2026-06-10
22 papers in source corpus 6 papers cited in narrative 6 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 4/5 claims corpus-supported (80%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

HMGXB4 (HMG2L1) is a nuclear HMG-box protein that functions as a sequence-specific transcriptional regulator coordinating inflammation, vascular cell differentiation, and developmental signaling (PMID:33563757, PMID:20511232). In innate immunity it acts as a direct transcriptional activator, binding the Nos2 (iNOS) promoter in macrophages and the Icam1 promoter in endothelial cells to drive proinflammatory gene expression; genetic deletion of Hmgxb4 protects mice from LPS- and CLP-induced lethality and lung injury (PMID:33563757). In the vasculature it represses smooth muscle differentiation by physically engaging myocardin through reciprocal N-terminal domains, displacing myocardin from SRF and abolishing SRF-myocardin occupancy of smooth muscle gene promoters (PMID:20511232), and its expression is induced by arterial injury (PMID:38644513). HMGXB4 also acts as a negative regulator of Wnt/beta-catenin signaling through the kinase NLK, inhibiting beta-catenin-driven axis duplication and target gene transcription (PMID:12875653), and it activates expression of the Sleeping Beauty transposase from the transposon 5'-UTR under negative feedback from the transposase itself (PMID:18071335). Its own expression and activity are controlled upstream by ERK2/ELK1 activation and KRAB-ZNF/TRIM28 repression, and post-translationally by SUMOylation, which governs nucleolar compartmentalization and partner-binding affinity (PMID:37108449).

Mechanistic history

Synthesis pass · year-by-year structured walk · 6 steps
  1. 2003 Medium

    Established HMGXB4 as the first-identified molecular link between an HMG-box protein and negative control of Wnt/beta-catenin signaling, answering how the pathway might be dampened downstream.

    Evidence Yeast two-hybrid identification of NLK interaction, Xenopus embryo axis-duplication assay, and mammalian beta-catenin reporter assay

    PMID:12875653

    Open questions at the time
    • Mechanism by which NLK-HMGXB4 interaction suppresses beta-catenin transcription not resolved
    • Direct DNA targets in the Wnt context not identified
    • Single lab, no structural data on the interaction
  2. 2007 Medium

    Showed HMGXB4 is a transcriptional activator of a defined regulatory element, revealing it directly upregulates Sleeping Beauty transposase expression within a feedback loop.

    Evidence Transcriptional reporter assays in human cells with deletion mapping of a 65-bp 5'-UTR region and transposase co-expression

    PMID:18071335

    Open questions at the time
    • Whether HMGXB4 binds the 65-bp element directly or via a partner not established
    • Endogenous physiological targets analogous to this element unknown
  3. 2010 High

    Defined a concrete repression mechanism in vascular biology by showing HMGXB4 disrupts the SRF-myocardin complex to suppress smooth muscle differentiation.

    Evidence GST pulldown domain mapping, reciprocal overexpression/siRNA in smooth muscle cells, and ChIP of smooth muscle gene promoters

    PMID:20511232

    Open questions at the time
    • In vivo role in vascular development or disease not addressed in this study
    • Structural basis of myocardin N-terminal interaction not solved
  4. 2021 High

    Established HMGXB4 as a direct proinflammatory transcriptional activator in vivo, identifying Nos2 and Icam1 as physiological promoter targets and linking the gene to sepsis pathology.

    Evidence Hmgxb4 knockout mice in LPS and CLP models, transcriptome profiling integrated with ChIP-seq, pharmacological NOS2 inhibition, and vascular permeability assays

    PMID:33563757

    Open questions at the time
    • DNA-binding specificity/consensus motif not defined
    • Cofactors enabling promoter activation not identified
    • Relationship between inflammatory and smooth-muscle/Wnt functions unresolved
  5. 2023 Medium

    Mapped the regulatory architecture controlling HMGXB4 itself, showing ERK2/ELK1 activation, KRAB-ZNF/TRIM28 repression, and SUMOylation-dependent nucleolar compartmentalization tune its activity.

    Evidence Reporter assays, ChIP, SUMOylation assays, subcellular localization experiments, and expression profiling in stem cells

    PMID:37108449

    Open questions at the time
    • SUMOylation sites and SUMO-dependent partner switches not enumerated
    • Several conclusions integrate prior published datasets rather than new direct assays
    • Functional consequence of nucleolar sequestration on target genes not quantified
  6. 2024 Medium

    Provided in vivo expression and localization context, confirming HMGXB4 is a broadly expressed nuclear protein induced by arterial injury.

    Evidence lacZ gene-trap knock-in reporter mouse with beta-galactosidase staining across tissues and an arterial injury model

    PMID:38644513

    Open questions at the time
    • Causal role of injury-induced expression in vascular remodeling not tested
    • Cell-type-specific function during injury not resolved

Open questions

Synthesis pass · forward-looking unresolved questions
  • How HMGXB4 reconciles its activator and repressor activities across inflammation, smooth muscle differentiation, and Wnt signaling — and what determines its DNA-binding specificity — remains unresolved.
  • No defined DNA consensus motif
  • No structural model of HMG-box DNA engagement or partner complexes
  • Integration of upstream regulation with context-specific target selection unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140110 transcription regulator activity 5 GO:0003677 DNA binding 2
Localization
GO:0005634 nucleus 1 GO:0005730 nucleolus 1
Pathway
R-HSA-74160 Gene expression (Transcription) 2 R-HSA-162582 Signal Transduction 1 R-HSA-168256 Immune System 1
Partners
ELK1MAPK1MYOCDNLKSRFTRIM28

Evidence

Reading pass · 6 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2003 HMG2L1 (HMGXB4) was identified as an NLK-binding protein via yeast two-hybrid screening. Injection of Xenopus HMG2L1 mRNA into Xenopus embryos inhibited Wnt/beta-catenin-induced axis duplication and target gene expression, and xHMG2L1 inhibited beta-catenin-stimulated transcriptional activity in mammalian cells, establishing HMG2L1 as a negative regulator of Wnt/beta-catenin signaling acting through NLK. Yeast two-hybrid screening, Xenopus mRNA injection (axis duplication assay), mammalian cell transcriptional reporter assay Genes to cells : devoted to molecular & cellular mechanisms Medium 12875653
2007 HMG2L1 (HMGXB4) upregulates transcription from the 5'-UTR of the Sleeping Beauty (SB) transposon, requiring a specific 65-bp region. The SB transposase antagonizes this HMG2L1-dependent upregulation, indicating a negative feedback regulation of transposase expression. Transcriptional reporter assays in human cells with HMG2L1 overexpression and SB transposase co-expression; deletion mapping of the 65-bp regulatory region Molecular therapy : the journal of the American Society of Gene Therapy Medium 18071335
2010 HMGXB4 (HMG2L1) physically interacts with myocardin via their respective N-terminal domains (mapped by GST pulldown), disrupts myocardin binding to SRF, and abolishes SRF-myocardin complex binding to promoters of smooth muscle-specific genes, thereby repressing smooth muscle differentiation. Overexpression of HMG2L1 in SMCs down-regulated smooth muscle marker expression, and depletion of endogenous HMG2L1 increased smooth muscle-specific gene expression. GST pulldown (interaction domain mapping), overexpression and siRNA knockdown in smooth muscle cells, gene expression analysis, chromatin immunoprecipitation (promoter binding) The Journal of biological chemistry High 20511232
2021 HMGXB4 functions as a transcriptional activator that directly binds the Nos2 (iNOS) promoter in macrophages and the Icam1 promoter in endothelial cells, driving proinflammatory gene expression. Genetic deletion of Hmgxb4 protected mice from LPS-induced lung injury and lethality and CLP-induced lethality, and attenuated LPS-induced proinflammatory gene expression in cultured macrophages. Genetic knockout in mice (LPS and CLP models), genome-wide transcriptome profiling integrated with ChIP-seq dataset, pharmacological NOS2 inhibition, vascular permeability assays Proceedings of the National Academy of Sciences of the United States of America High 33563757
2023 HMGXB4 is activated transcriptionally by ERK2/MAPK1 and ELK1, is suppressed by the KRAB-ZNF/TRIM28 epigenetic repression machinery, and is post-translationally regulated by SUMOylation, which modulates its binding affinity to protein interaction partners and controls its transcriptional activator function via nucleolar compartmentalization. HMGXB4 participates in nuclear-remodeling protein complexes and transactivates target gene expression in vertebrates, and it targets Sleeping Beauty transposition to germinal stem cells by activating transposase expression. Reporter assays, ChIP, SUMOylation assays, subcellular localization (nucleolar compartmentalization) experiments, chromatin domain analysis, expression profiling in germinal and somatic stem cells International journal of molecular sciences Medium 37108449
2024 HMGXB4 is a nuclear protein widely expressed in mouse tissues. Arterial injury significantly induces Hmgxb4 expression, as demonstrated by a gene trap (lacZ knock-in) reporter mouse model in which β-galactosidase activity mirrors endogenous Hmgxb4 promoter activity. Gene trap mouse model (lacZ insertion into Hmgxb4 locus), β-galactosidase staining across tissues, arterial injury model Physiological reports Medium 38644513

Source papers

Stage 0 corpus · 22 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1999 Regulation of p53 function and stability by phosphorylation. Molecular and cellular biology 386 10022862
2005 Single-stranded DNA mimicry in the p53 transactivation domain interaction with replication protein A. Proceedings of the National Academy of Sciences of the United States of America 237 16234232
2007 Transcriptional activities of the Sleeping Beauty transposon and shielding its genetic cargo with insulators. Molecular therapy : the journal of the American Society of Gene Therapy 75 18071335
1987 Structural proteins of bovine coronavirus and their intracellular processing. The Journal of general virology 67 3681266
2015 Sleeping Beauty Transposition. Microbiology spectrum 40 26104705
2009 Interaction between the transactivation domain of p53 and PC4 exemplifies acidic activation domains as single-stranded DNA mimics. The Journal of biological chemistry 40 19525231
2003 Negative regulation of Wnt signalling by HMG2L1, a novel NLK-binding protein. Genes to cells : devoted to molecular & cellular mechanisms 29 12875653
1991 Comparison of bovine coronavirus (BCV) antigens: monoclonal antibodies to the spike glycoprotein distinguish between vaccine and wild-type strains. Virology 27 2053295
2010 Repression of smooth muscle differentiation by a novel high mobility group box-containing protein, HMG2L1. The Journal of biological chemistry 20 20511232
1999 TOM1 genes map to human chromosome 22q13.1 and mouse chromosome 8C1 and encode proteins similar to the endosomal proteins HGS and STAM. Genomics 20 10329004
2008 Gene-based SNP mapping of a psychotic bipolar affective disorder linkage region on 22q12.3: association with HMG2L1 and TOM1. American journal of medical genetics. Part B, Neuropsychiatric genetics : the official publication of the International Society of Psychiatric Genetics 18 17671966
2011 Anchoring intrinsically disordered proteins to multiple targets: lessons from N-terminus of the p53 protein. International journal of molecular sciences 16 21541066
2021 Deficiency of the novel high mobility group protein HMGXB4 protects against systemic inflammation-induced endotoxemia in mice. Proceedings of the National Academy of Sciences of the United States of America 11 33563757
2017 Effects of the RGD loop and C-terminus of rhodostomin on regulating integrin αIIbβ3 recognition. PloS one 11 28399159
2023 HMGXB4 Targets Sleeping Beauty Transposition to Germinal Stem Cells. International journal of molecular sciences 3 37108449
2024 A novel mouse model carrying a gene trap insertion into the Hmgxb4 gene locus to examine Hmgxb4 expression in vivo. Physiological reports 1 38644513
2024 PDGF-BB overexpression in p53 null oligodendrocyte progenitors increases H3K27me3 and induces transcriptional changes which favor proliferation. Neoplasia (New York, N.Y.) 1 39216363
2026 Exosomal miRNA-mRNA interactions highlight MSC-like molecular signatures in dental pulp fibroblasts. Stem cell research & therapy 0 41521291
2026 Real-world-data for phenotypes and genotypes of rare monogenic genetic epilepsies and genes of uncertain significance for epilepsy. Epilepsia open 0 42220229
2024 PDGF-BB overexpression in p53 null oligodendrocyte progenitors increases H3K27me3 and induces transcriptional changes which favor proliferation. bioRxiv : the preprint server for biology 0 38798631
2024 Biallelic HMGXB4 loss-of-function variant causes intellectual disability, developmental delay, and dysmorphic features. Heliyon 0 39166056
2021 Analysis of the P53N a Novel Protein Encoded on Chromosome 22q12.1-12.3 in Glioblastomas and Ependymomas Specimens. Journal of molecular neuroscience : MN 0 33595778

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