XBP1 Antibody – Rabbit Polyclonal

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]

XBP1: a transcription factor essential for hepatocyte growth, the differentiation of plasma cells, immunoglobulin secretion, and the unfolded protein response (UPR). XBP1 mRNA is spliced by IRE1 during the UPR to generate a new C-terminus, converting it into a potent unfolded-protein response transcriptional activator and triggering growth arrest and apoptosis. Only the spliced form of XBP1 can activate the UPR efficiently. Activates UPR target genes via direct binding to the UPR element (UPRE). Binds DNA preferably to the CRE-like element 5'-GATGACGTG[TG]N(3)[AT]T-3', and also to some TPA response elements (TRE). Binds to the HLA DR-alpha promoter. Binds to the Tax-responsive element (TRE) of HTLV-I. Up-regulated by ATF6 via direct binding to the ERSE in response to endoplasmic reticulum stress. Genetic variations in XBP1 could be associated with susceptibility to major affective disorder type 7 (MAFD7). Major affective disorders represent a class of mental disorders characterized by a disturbance in mood as their predominant feature. Two human isoforms are produced by alternative splicing. Isoform 1 is also known as XBP-1U. Isoform 2, also known as XBP-1S, is produced by IRE1 in response to endoplasmic reticulum stress. IRE1 cleaves a 26-bp fragment causing a frameshift of the mRNA transcript.

Protein type: DNA-binding; Transcription factor

Chromosomal Location of Human Ortholog: 22q12.1|22q12

Cellular Component: cytoplasm; cytosol; endoplasmic reticulum; endoplasmic reticulum membrane; integral to endoplasmic reticulum membrane; integral to membrane; nucleoplasm; nucleus

Molecular Function: chromatin DNA binding; DNA binding; estrogen receptor binding; histone deacetylase binding; protease binding; protein binding; protein heterodimerization activity; protein homodimerization activity; protein kinase binding; transcription factor activity; ubiquitin protein ligase binding

Biological Process: angiogenesis; autophagy; cell growth; cellular response to glucose starvation; cellular response to insulin stimulus; cellular response to nutrient; cholesterol homeostasis; endothelial cell proliferation; exocrine pancreas development; fatty acid biosynthetic process; fatty acid homeostasis; immune response; liver development; muscle development; negative regulation of apoptosis; negative regulation of transcription from RNA polymerase II promoter; neuron development; organelle organization and biogenesis; phosphoinositide 3-kinase cascade; positive regulation of autophagy; positive regulation of B cell differentiation; positive regulation of fat cell differentiation; positive regulation of histone methylation; positive regulation of immunoglobulin production; positive regulation of immunoglobulin secretion; positive regulation of MHC class II biosynthetic process; positive regulation of protein amino acid phosphorylation; positive regulation of T cell differentiation; positive regulation of TOR signaling pathway; positive regulation of transcription factor import into nucleus; positive regulation of transcription from RNA polymerase II promoter; positive regulation of transcription of target genes involved in unfolded protein response; protein destabilization; protein transport; regulation of autophagy; regulation of protein stability; sterol homeostasis; transcription from RNA polymerase II promoter; ubiquitin-dependent protein catabolic process; unfolded protein response; vascular endothelial growth factor receptor signaling pathway

Disease: Major Affective Disorder 7