Research Papers:

Molecular mechanisms of human IRE1 activation through dimerization and ligand binding

Amar Joshi, Yvette Newbatt, P. Craig McAndrew, Mark Stubbs, Rosemary Burke, Mark W. Richards, Chitra Bhatia, John J. Caldwell, Tatiana McHardy, Ian Collins and Richard Bayliss _

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Oncotarget. 2015; 6:13019-13035. https://doi.org/10.18632/oncotarget.3864

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Amar Joshi1,2, Yvette Newbatt3, P. Craig McAndrew3, Mark Stubbs3, Rosemary Burke3, Mark W. Richards1,2, Chitra Bhatia1,2, John J. Caldwell3, Tatiana McHardy3, Ian Collins3 and Richard Bayliss1,2

1 Department of Biochemistry, University of Leicester, Leicester, United Kingdom

2 Cancer Research UK Leicester Centre, University of Leicester, Leicester, United Kingdom

3 Cancer Research UK Cancer Therapeutics Unit, Division of Cancer Therapeutics, The Institute of Cancer Research, London, United Kingdom

Correspondence to:

Richard Bayliss, email:

Ian Collins, email:

Keywords: UPR, drug discovery, kinase, RNase

Received: December 02, 2014 Accepted: March 31, 2015 Published: April 18, 2015


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.

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