Background：X-box-binding protein 1(XBP1), also named as TREB5, is a 261 amino acid protein, which contains one bZIP domain and belongs to the bZIP family. XBP1 localizes in the nucleus and as a transcription factor is essential for hepatocyte growth, the differentiation of plasma cells, the immunoglobulin secretion, and the unfolded protein response. XBP1 has an association with major affective disorder. The molecular weight of protein generated from the spliced XBP1 mRNA is 54 kDa and protein generated from unspliced Xbp1 mRNA is 33 kDa.
