XBP1

该基因编码一种转录因子，通过与一种称为x盒的启动子元件结合来调节mhcⅡ类基因。这种基因产物是一种bZIP蛋白，它也被鉴定为一种细胞转录因子，与T细胞白血病病毒1型启动子启动子中的增强子结合它可能通过充当病毒反式激活因子的dna结合伙伴来增加病毒蛋白的表达。已经发现，在内质网（er）中积累未折叠蛋白后，该基因的mrna通过一种非传统的剪接机制被加工成活性形式，该剪接机制由需要酶1（ire1）介导。从剪接的mrna中丢失26nt导致帧移位和xbp1（s）亚型，xbp1（s）是功能活跃的转录因子。由未切片的mrna xbp1（u）编码的亚型被组成性表达，并被认为是xbp1（s）的负反馈调节因子，它在内质网应激恢复期阻断靶基因的转录。XBP1的一个假基因已经被鉴定并定位在5号染色体上。[由RefSeq提供，2008年7月]
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]