GSK3β-SCFFBXW7α mediated phosphorylation and ubiquitination of IRF1 are required for its transcription-dependent turnover

Garvin, Alexander J.; Khalaf, Ahmed H.A.; Rettino, Alessandro; Xicluna, Jerome; Butler, Laura; Morris, Joanna R.; Heery, David M.; Clarke, Nicole M.

Abstract

IRF1 (Interferon Regulatory Factor-1) is the prototype of the IRF family of DNA binding transcription factors. IRF1 protein expression is regulated by transient up-regulation in response to external stimuli followed by rapid degradation via the ubiquitin-proteasome system. Here we report that DNA bound IRF1 turnover is promoted by GSK3β (Glycogen Synthase Kinase 3β) via phosphorylation of the T181 residue which generates a phosphodegron for the SCF (Skp-Cul-Fbox) ubiquitin E3-ligase receptor protein Fbxw7α (F-box/WD40 7). This regulated turnover is essential for IRF1 activity, as mutation of T181 results in an improperly stabilised protein that accumulates at target promoters but fails to induce RNA-Pol-II elongation and subsequent transcription of target genes. Consequently, the anti-proliferative activity of IRF1 is lost in cell lines expressing T181A mutant. Further, cell lines with dysfunctional Fbxw7 are less sensitive to IRF1 overexpression, suggesting an important co-activator function for this ligase complex. As T181 phosphorylation requires both DNA binding and RNA-Pol-II elongation, we propose that this event acts to clear " spent " molecules of IRF1 from transcriptionally engaged target promoters.

Citation

Garvin, A. J., Khalaf, A. H., Rettino, A., Xicluna, J., Butler, L., Morris, J. R., …Clarke, N. M. (2019). GSK3β-SCFFBXW7α mediated phosphorylation and ubiquitination of IRF1 are required for its transcription-dependent turnover. Nucleic Acids Research, 47(9), 4476-4494. https://doi.org/10.1093/nar/gkz163

• Journal Article Type: Article
• Acceptance Date: Mar 7, 2019
• Online Publication Date: Mar 11, 2019
• Publication Date: May 21, 2019
• Deposit Date: Mar 6, 2019
• Publicly Available Date: May 14, 2019
• Journal: Nucleic Acids Research
• Print ISSN: 0305-1048
• Electronic ISSN: 1362-4962
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 47
• Issue: 9
• Article Number: gkz163
• Pages: 4476-4494
• DOI: https://doi.org/10.1093/nar/gkz163
• Keywords: Interferon Regulatory Factor-1; phosphodegron; GSK3; FBXW7
• Public URL: https://nottingham-repository.worktribe.com/output/1612445
• Publisher URL: https://academic.oup.com/nar/article/47/9/4476/5373034
• Contract Date: May 14, 2019