Abstract: ABSTRACT:X-box binding protein 1 is an important component of unfolded protein response.XBP-1 has two splicing variants that were designated XBP-1S and XBP-1U. The former activity is much higher than the latter. When the cell is on the condition of endoplasmic reticulum stress, XBP-1 is induced by ATF6,and spliced by IRE1,then the functional XBP-1S was transcripted, and activation of unfolded protein response. XBP-1 is an important transcription factor,it has an important regulatory role on cell growth and differentiation.XBP-1 is involved in the genesis,development of many diseases.