Seroatlas · Human Serome Atlas

XBP1

X-box-binding protein 1

Also known as: XBP1_HUMAN, XBP2

Cross-references: UniProt · Ensembl · Human Protein Atlas · GeneCards · NCBI Gene

Protein identityUniProt · HPA

UniProt accession
P17861
Gene
XBP1
Ensembl
ENSG00000100219
Chromosome
22
Canonical length
261 aa
Protein class
Cancer-related genes, Disease related genes, Human disease related genes, Predicted intracellular proteins, Predicted membrane proteins, Transcription factors

OverviewNCBI Gene

This gene encodes a transcription factor that regulates MHC class II genes by binding to a promoter element referred to as an X box. This gene product is a bZIP protein, which was also identified as a cellular transcription factor that binds to an enhancer in the promoter of the T cell leukemia virus type 1 promoter. It may increase expression of viral proteins by acting as the DNA binding partner of a viral transactivator. It has been found that upon accumulation of unfolded proteins in the endoplasmic reticulum (ER), the mRNA of this gene is processed to an active form by an unconventional splicing mechanism that is mediated by the endonuclease inositol-requiring enzyme 1 (IRE1). The resulting loss of 26 nt from the spliced mRNA causes a frame-shift and an isoform XBP1(S), which is the functionally active transcription factor. The isoform encoded by the unspliced mRNA, XBP1(U), is constitutively expressed, and thought to function as a negative feedback regulator of XBP1(S), which shuts off transcription of target genes during the recovery phase of ER stress. A pseudogene of XBP1 has been identified and localized to chromosome 5. [provided by RefSeq, Jul 2008]

Canonical amino-acid sequenceUniProt

261 residues, UniProt reviewed canonical sequence.

>P17861|XBP1
     1  MVVVAAAPNP ADGTPKVLLL SGQPASAAGA PAGQALPLMV PAQRGASPEA ASGGLPQARK
    61  RQRLTHLSPE EKALRRKLKN RVAAQTARDR KKARMSELEQ QVVDLEEENQ KLLLENQLLR
   121  EKTHGLVVEN QELRQRLGMD ALVAEEEAEA KGNEVRPVAG SAESAALRLR APLQQVQAQL
   181  SPLQNISPWI LAVLTLQIQS LISCWAFWTT WTQSCSSNAL PQSLPAWRSS QRSTQKDPVP
   241  YQPPFLCQWG RHQPSWKPLM N

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against XBP1 can act on the native protein depends on physical access: surface and secreted proteins are reachable by circulating antibodies, intracellular proteins usually are not.

Antibody reachability
Other membrane
Secreted
No
Transmembrane segments
1
Mean surface accessibility (rSASA)
0.61
Highest tissue expression
1,102 nTPM

Expression across tissuesHPA

Tissue

  • pancreas: 1,102 nTPM
  • salivary gland: 793 nTPM
  • breast: 676 nTPM
  • liver: 643 nTPM
  • cervix: 348 nTPM
  • tonsil: 289 nTPM

Single-cell type

  • breast hormone-responsive cells: 3,630 nCPM
  • plasma cells: 2,196 nCPM
  • pancreatic acinar cells: 1,038 nCPM
  • respiratory secretory cells: 959 nCPM
  • breast lactating cells: 926 nCPM
  • salivary acinar cells: 821 nCPM

Immune cell

  • basophil: 176 nTPM
  • MAIT T-cell: 89 nTPM
  • NK-cell: 87 nTPM
  • plasmacytoid DC: 73 nTPM
  • memory CD8 T-cell: 70 nTPM
  • gdT-cell: 69 nTPM

Brain region

  • choroid plexus: 75 nTPM
  • thalamus: 47 nTPM
  • medulla oblongata: 46 nTPM
  • midbrain: 46 nTPM
  • hypothalamus: 45 nTPM
  • spinal cord: 43 nTPM

DiseaseUniProt · ClinVar · IEDB · PubMed

Four sources answering four different questions about XBP1.

Disease | AllUniProt

Conditions XBP1 is implicated in, by any mechanism.

Disease | ImmuneIEDB

Conditions an epitope on XBP1 was assayed in.

Genetic constraint and essentialitygnomAD · DepMap

Does the body need this protein intact? Low LOEUF or a strong DepMap dependency means loss or blockade of the protein is likely to be felt.

gnomAD LOEUF (loss-of-function intolerance)
0.73
gnomAD pLI
0.03
gnomAD missense Z
1.02
DepMap mean gene effect
0.08
DepMap dependency class
selective

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 4% of surveyed tumor types (aggregate summary; per-cohort expression, alteration, and survival load in the interactive view).

OntologyGO

Biological processes

Molecular functions

Cellular components

Protein domainsUniProt · Pfam · InterPro

KeywordsUniProt

InteractionsUniProt · HPA

Protein binding partners of XBP1 in the human serome: UniProt-annotated complex subunits plus reported interactors. Each links to its own Seroatlas record.

Antibody and autoantibody relevanceSeroatlas analysis

Seroatlas reads XBP1 as an antibody target. Whether an autoantibody or antibody against XBP1 could matter depends on whether native XBP1 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

XBP1 is annotated as predominantly intracellular. Intracellular proteins are common autoantibody markers, becoming visible to the immune system after cell injury or altered processing, but are usually markers of disease rather than direct drivers.

Annotation status

The present source text does not explicitly label XBP1 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

Canonical record: https://seroatlas.com/gene/XBP1. Study-independent annotations aggregated from UniProt, Human Protein Atlas, PubMed, IEDB, Pfam, InterPro, Gene Ontology, AlphaFold, gnomAD, DepMap, ClinVar, TCGA. Catalog release seroatlas-reviewed-human-uniprot-20260313.

Seroatlas is the reference for exploring autoantibody and antibody serology at the human-protein level: the autoreactome and human serome, multiplex serology (HuProt, HuScan, VirScan, PhIP-Seq).

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