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In the unfolded protein response, the type I transmembrane protein Ire1 transmits an endoplasmic reticulum (ER) stress signal to the cytoplasm. We previously reported that under nonstressed conditions, the ER chaperone BiP binds and represses Ire1. It is still unclear how this event contributes to the overall regulation of Ire1. The present Ire1 mutation(More)
Chaperone protein BiP binds to Ire1 and dissociates in response to endoplasmic reticulum (ER) stress. However, it remains unclear how the signal transducer Ire1 senses ER stress and is subsequently activated. The crystal structure of the core stress-sensing region (CSSR) of yeast Ire1 luminal domain led to the controversial suggestion that the molecule can(More)
Upon endoplasmic reticulum (ER) stress, an endoribonuclease, inositol-requiring enzyme-1α, splices the precursor unspliced form of X-box-binding protein 1 messenger RNA (XBP1u mRNA) on the ER membrane to yield an active transcription factor (XBP1s), leading to the alleviation of the stress. The nascent peptide encoded by XBP1u mRNA drags the(More)
Eukaryotic cells activate the unfolded-protein response (UPR) upon endoplasmic reticulum (ER) stress, where the stress is assumed to be the accumulation of unfolded proteins in the ER. Consistent with previous in vitro studies of the ER-luminal domain of the mutant UPR initiator Ire1, our study show its association with a model unfolded protein in yeast(More)
Accumulation of unfolded proteins in the endoplasmic reticulum (ER) accompanies ER stress and causes the type-I transmembrane protein Ire1 (also known as ERN1) to trigger the unfolded protein response (UPR). When dimerized, the core stress-sensing region (CSSR) of Ire1 directly captures unfolded proteins and forms a high-order oligomer, leading to(More)
Molecular chaperones prevent aggregation of denatured proteins in vitro and are thought to support folding of diverse proteins in vivo. Chaperones may have some selectivity for their substrate proteins, but knowledge of particular in vivo substrates is still poor. We here show that yeast Rot1, an essential, type-I ER membrane protein functions as a(More)
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