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RESEARCH ARTICLE |
Skirball Institute of Biomolecular Medicine, the Departments of Medicine, Cell Biology, and the Kaplan Cancer Center, New York University School of Medicine, New York, NY 10016, USA
*Author for correspondence (e-mail: ron{at}saturn.med.nyu.edu)
Accepted May 22, 2001
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.
Key words: Endoplasmic reticulum, Protein kinase, Ribonuclease, RNA Processing, Signal transduction
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