Cleavage of Xbp1 mRNA by IRE1alpha and Splicing of Cleaved Xbp1 mRNA Authored: May, B, 2009-06-03 Edited: May, B, 2009-06-03 Phosphorylated IRE1-alpha homodimers with bound ADP have endoribonuclease activity in their C-terminal (cytosolic) regions. The IRE1-alpha homodimers cleave an internal 26 nucleotide segment out of the Xbp-1 mRNA. In yeast the resulting RNAs are ligated by a tRNA ligase but the corresponding human ligase has not been identified. The cleavage and ligation leads to a frameshift in the Xbp-1 mRNA which results in a longer ORF that encodes Xbp-1 (S), the active form of the Xbp-1 transcription factor Pubmed11779464 Pubmed17026957 Pubmed18242182 Pubmed19622636 Reactome Database ID Release 43425923 Reactome, http://www.reactome.org ReactomeREACT_22313 Reviewed: D'Eustachio, P, Matthews, L, Gillespie, ME, 2008-12-02 16:25:31 Reviewed: Urano, F, 2010-04-30 Xbp1 mRNA (spliced) Xbp1 mRNA (unspliced)