Anti-XBP1 Antibody Picoband® Fluoro488 Conjugated

XBP1, also known as X-box binding protein 1, is a protein which in humans is encoded by the XBP1 gene. It 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.

X-box-binding protein 1 ; XBP-1 ; Tax-responsive element-binding protein 5 ; TREB-5 ; X-box-binding protein 1, cytoplasmic form ; X-box-binding protein 1, luminal form ; XBP1 ; TREB5 , XBP2

Expressed in plasma cells in rheumatoid synovium (PubMed:11460154) . Over-expressed in primary breast cancer and metastatic breast cancer cells (PubMed:25280941) . Isoform 1 and isoform 2 are expressed at higher level in proliferating as compared to confluent quiescent endothelial cells (PubMed:19416856) . .

Functions as a transcription factor during endoplasmic reticulum (ER) stress by regulating the unfolded protein response (UPR) . Required for cardiac myogenesis and hepatogenesis during embryonic development, and the development of secretory tissues such as exocrine pancreas and salivary gland (By similarity) . Involved in terminal differentiation of B lymphocytes to plasma cells and production of immunoglobulins (PubMed:11460154) . Modulates the cellular response to ER stress in a PIK3R-dependent manner (PubMed:20348923) . Binds to the cis-acting X box present in the promoter regions of major histocompatibility complex class II genes (PubMed:8349596) . Involved in VEGF-induced endothelial cell (EC) proliferation and retinal blood vessel formation during embryonic development but also for angiogenesis in adult tissues under ischemic conditions. Functions also as a major regulator of the UPR in obesity-induced insulin resistance and type 2 diabetes for the management of obesity and diabetes prevention (By similarity) . .

1. Entrez Gene: XBP1 X-box binding protein 1. 2. Ono SJ, Liou HC, Davidon R, Strominger JL, Glimcher LH (May 1991) . Human X-box-binding protein 1 is required for the transcription of a subset of human class II major histocompatibility genes and forms a heterodimer with c-fos. Proc. Natl. Acad. Sci. U.S.A. 88 (10) : 4309–12. 3. Yoshida H, Nadanaka S, Sato R, Mori K (2006) . XBP1 is critical to protect cells from endoplasmic reticulum stress: evidence from Site-2 protease-deficient Chinese hamster ovary cells. Cell Structure and Function 31 (2) : 117–25.

Endoplasmic reticulum . Colocalizes with ERN1 and KDR in the endoplasmic reticulum in endothelial cells in a vascular endothelial growth factor (VEGF) -dependent manner (PubMed:23529610) . .