Sequence of this protein is as follows: MVVVAAAPNP ADGTPKVLLL SGQPASAAGA PAGQALPLMV PAQRGASPEA ASGGLPQARK RQRLTHLSPE EKALRRKLKN RVAAQTARDR KKARMSELEQ QVVDLEEENQ KLLLENQLLR EKTHGLVVEN QELRQRLGMD ALVAEEEAEA KGNEVRPVAG SAESAALRLR APLQQVQAQL SPLQNISPWI LAVLTLQIQS LISCWAFWTT WTQSCSSNAL PQSLPAWRSS QRSTQKDPVP YQPPFLCQWG RHQPSWKPLM N
XBP1 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.
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Protein Aliases: OTTHUMP00000028682; Tax-responsive element-binding protein 5; TREB-5; X-box-binding protein 1; X-box-binding protein 1, cytoplasmic form; X-box-binding protein 1, luminal form; XBP-1
Gene Aliases: TREB-5; TREB5; XBP-1; XBP1; XBP2
UniProt ID: (Human) P17861
Entrez Gene ID: (Human) 7494