The bZIP intron RNA motif is an RNA structure guiding splicing of a non-canonical intron from bZIP-containing genes called HAC1 in yeast, XBP1 in Metazoa, Hxl1 or Cib1 in Basidiomycota and bZIP60 in plants. Splicing is performed independently of the spliceosome by Ire1, a kinase with endoribonuclease activity. Exons are joined by a tRNA ligase. Recognition of the intron splice sites is mediated by a base-paired secondary structure of the mRNA that forms at the exon/intron boundaries. Splicing of the bZIP intron is a key regulatory step in the unfolded protein response (UPR). The Ire-mediated unconventional splicing was first described for HAC1 in S. cerevisiae.