Bypass of activation loop phosphorylation by aspartate 836 in activation of the endoribonuclease activity of Ire1

Armstrong, M.C.; Sestak, S.; Ali, A.A.; Sagini, H.A.M.; Brown, M.; Baty, K.; Treumann, A.; Schröder, M.

Abstract

The bifunctional protein kinase-endoribonuclease Ire1 initiates splicing of the mRNA for the transcription factor Hac1 when unfolded proteins accumulate in the endoplasmic reticulum. Activation of Saccharomyces cerevisiae Ire1 coincides with autophosphorylation of its activation loop at S840, S841, T844, and S850. Mass spectrometric analysis of Ire1 expressed in Escherichia coli identified S837 as another potential phosphorylation site in vivo. Mutation of all five potential phosphorylation sites in the activation loop decreased, but did not completely abolish, splicing of HAC1 mRNA, induction of KAR2 and PDI1 mRNAs, and expression of a β-galactosidase reporter activated by Hac1i. Phosphorylation site mutants survive low levels of ER stress better than IRE1 deletions strains. In vivo clustering and inactivation of Ire1 are not affected by phosphorylation site mutants. Mutation of D836 to alanine in the activation loop of phosphorylation site mutants nearly completely abolished HAC1 splicing, induction of KAR2, PDI1, and β-galactosidase reporters, and survival of ER stress, but had no effect on clustering of Ire1. By itself, the D836A mutation does not confer a phenotype. These data argue that D836 can partially substitute for activation loop phosphorylation in activation of the endoribonuclease domain of Ire1.

Citation

Armstrong, M., Sestak, S., Ali, A., Sagini, H., Brown, M., Baty, K., …Schröder, M. (2017). Bypass of activation loop phosphorylation by aspartate 836 in activation of the endoribonuclease activity of Ire1. Molecular and Cellular Biology, 37(16), e00655-16. https://doi.org/10.1128/mcb.00655-16

• Journal Article Type: Article
• Acceptance Date: May 22, 2017
• Online Publication Date: May 30, 2017
• Publication Date: Aug 1, 2017
• Deposit Date: Dec 9, 2016
• Publicly Available Date: May 24, 2017
• Journal: Molecular and Cellular Biology
• Print ISSN: 0270-7306
• Electronic ISSN: 1098-5549
• Publisher: American Society for Microbiology
• Peer Reviewed: Peer Reviewed
• Volume: 37
• Issue: 16
• Article Number: e00655-16
• Pages: e00655-16
• DOI: https://doi.org/10.1128/mcb.00655-16
• Public URL: https://durham-repository.worktribe.com/output/1367519