Alterations in an IRE1-RNA complex in the mammalian unfolded protein response.
IRE1 proteins mediate cellular responses to accumulation of malfolded proteins in the endoplasmic reticulum in the yeast and mammalian unfolded protein responses. A sensitive in vivo u.v. crosslinking assay showed that IRE1 proteins are intimately associated with RNA in mammalian cells. The IRE1-associated RNA fragments recovered by this assay were different in stressed and unstressed cells. The amount of RNA associated with IRE1 that could be revealed by end-labeling with T4 kinase was greater in IRE1-containing complexes isolated from stressed cells. Furthermore, the RNA fragments recovered from complexes found in stressed cells were shorter than those from unstressed cells, revealing a dynamic change in the IRE1-RNA complex during the UPR. Formation of the complex between IRE1 and RNA was dependent on both the kinase and endonuclease domains of IRE1, and involved pre-existing RNA species. When viewed in the context of the known importance of Ire1p-HAC1 mRNA interactions to the yeast unfolded protein response, these findings suggest that full-length mammalian IRE1s also engage RNA molecules as downstream effectors.
Bertolotti
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Skirball Institute of Biomolecular Medicine, and the Kaplan Cancer Center, New York University School of Medicine, New York, NY 10016, USA.
Ron
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D000818:Animals; D002478:Cells, Cultured; D003609:Dactinomycin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004722:Endoribonucleases; D006801:Humans; D008565:Membrane Proteins; D011233:Precipitin Tests; D017510:Protein Folding; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000378:metabolism*; D012313:RNA / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D013312:Stress, Physiological; D013997:Time Factors; D014162:Transfection
D008565:Membrane Proteins; D012333:RNA, Messenger; D003609:Dactinomycin; D012313:RNA; D011494:Protein Kinases; C403982:ERN2 protein, human; C486557:Ern2 protein, rat; D017346:Protein Serine-Threonine Kinases; D004722:Endoribonucleases