title: Arabidopsis IRE1 catalyses unconventional splicing of bZIP60 mRNA to produce the active transcription factor.
abstract: IRE1 plays an essential role in the endoplasmic reticulum (ER) stress response in yeast and mammals. We found that a double mutant of Arabidopsis IRE1A and IRE1B (ire1a/ire1b) is more sensitive to the ER stress inducer tunicamycin than the wild-type. Transcriptome analysis revealed that genes whose induction was reduced in ire1a/ire1b largely overlapped those in the bzip60 mutant. We observed that the active form of bZIP60 protein detected in the wild-type was missing in ire1a/ire1b. We further demonstrated that bZIP60 mRNA is spliced by ER stress, removing 23 ribonucleotides and therefore causing a frameshift that replaces the C-terminal region of bZIP60 including the transmembrane domain (TMD) with a shorter region without a TMD. This splicing was detected in ire1a and ire1b single mutants, but not in the ire1a/ire1b double mutant. We conclude that IRE1A and IRE1B catalyse unconventional splicing of bZIP60 mRNA to produce the active transcription factor.
authors.affiliation: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuencho, Nakaku, Sakai, Osaka, 599-8531, Japan.
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Nagashima
authors.forename: Kei-Ichiro
authors.initials: K
authors.lastname: Mishiba
authors.forename: Eiji
authors.initials: E
authors.lastname: Suzuki
authors.forename: Yukihisa
authors.initials: Y
authors.lastname: Shimada
authors.forename: Yuji
authors.initials: Y
authors.lastname: Iwata
authors.forename: Nozomu
authors.initials: N
authors.lastname: Koizumi
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics*; D055162:Biocatalysis; D016133:Polymerase Chain Reaction; D011494:Protein Kinases / Q000378:metabolism*; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism*; D059467:Transcriptome; D014415:Tunicamycin / Q000494:pharmacology
chemical_list: D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D012333:RNA, Messenger; D014157:Transcription Factors; C533092:bZIP60 protein, Arabidopsis; D014415:Tunicamycin; D011494:Protein Kinases; C446528:Ire1-2 protein, Arabidopsis