X-box Binding Protein 1 (X Box Binding Protein 1, XBP 1, XBP1, XBP-1, OTTHUMP00000028682, Tax Responsive Element Binding Protein 5, TREB5, X-box Binding Protein 2, XBP2)

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] Applications: Suitable for use in ELISA and Western Blot. Other applications have not been tested, Recommended Dilution: ELISA 1:4000, Western Blot 1-3ug/ml, Western Blot: 1-3ug/ml. Optimal dilutions to be determined by the researcher. Positive Control: ~Supplied as a liquid in Tris-saline, pH7.3, 0.5% BSA, 0.02% sodium azide. 38kD band observed in Nuclear lysates of cell line HeLa (calculated MW of 40.1kD according to NP_001073007.1). Storage and Stability: May be stored at 4 degrees C for short-term only. For long-term storage and to avoid repeated freezing and thawing, add sterile glycerol (40-50%), aliquot and store at -20 degrees C. Aliquots are stable for at least 3 months at -20 degrees C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.