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Molecular mechanisms of human IRE1 activation through dimerization and ligand binding

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posted on 21.05.2015, 09:36 by Amar Joshi, Y Newbatt, P. C. McAndrew, M. Stubbs, R. Burke, Mark W. Richards, Chitra Bhatia, J. J. Caldwell, T. McHardy, I. Collins, Richard Bayliss
IRE1 transduces the unfolded protein response by splicing XBP1 through its C-terminal cytoplasmic kinase-RNase region. IRE1 autophosphorylation is coupled to RNase activity through formation of a back-to-back dimer, although the conservation of the underlying molecular mechanism is not clear from existing structures. We have crystallized human IRE1 in a back-to-back conformation only previously seen for the yeast homologue. In our structure the kinase domain appears primed for catalysis but the RNase domains are disengaged. Structure-function analysis reveals that IRE1 is autoinhibited through a Tyr-down mechanism related to that found in the unrelated Ser/Thr protein kinase Nek7. We have developed a compound that potently inhibits human IRE1 kinase activity while stimulating XBP1 splicing. A crystal structure of the inhibitor bound to IRE1 shows an increased ordering of the kinase activation loop. The structures of hIRE in apo and ligand-bound forms are consistent with a previously proposed model of IRE1 regulation in which formation of a back-to-back dimer coupled to adoption of a kinase-active conformation drive RNase activation. The structures provide opportunities for structure-guided design of IRE1 inhibitors


This work was supported by Cancer Research UK grants (C24461/ A13231 and A12772 to R.B.) and (C309/A11566 to Cancer Therapeutics Unit, ICR).



Oncotarget, 2015

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/Organisation/COLLEGE OF MEDICINE, BIOLOGICAL SCIENCES AND PSYCHOLOGY/School of Biological Sciences/Department of Biochemistry


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PMID: 25968568 [PubMed - as supplied by publisher]. Atomic coordinates and structure factors for apohIRE1 and compound 3-hIRE have been deposited in the PDB, accession codes 4Z7G and 4Z7H respectively.



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