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Multivalent Interactions with Fbw7 and Pin1 Facilitate Recognition of c-Jun by the SCFFbw7 Ubiquitin Ligase.

Csizmok V, Montecchio M, Lin H, Tyers M, Sunnerhagen M, Forman-Kay JD

Molecular Medicine, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.

Many regulatory proteins, including the transcription factor c-Jun, are highly enriched in disordered protein regions that govern growth, division, survival, differentiation, and response to signals. The stability of c-Jun is controlled by poorly understood regulatory interactions of its disordered region with both the E3 ubiquitin ligase SCFFbw7 and prolyl cis-trans isomerase Pin1. We use nuclear magnetic resonance and fluorescence studies of c-Jun to demonstrate that multisite c-Jun phosphorylation is required for high-affinity interaction with Fbw7. We show that the Pin1 WW and PPIase domains interact in a dynamic complex with multiply phosphorylated c-Jun. Importantly, Pin1 isomerizes a pSer-Pro peptide bond at the c-Jun N terminus that affects binding to Fbw7 and thus modulates the ubiquitin-mediated degradation of c-Jun. Our findings support the general principle that multiple weak binding motifs within disordered regions can synergize to yield high-affinity interactions and provide rapidly evolvable means to build and fine-tune regulatory events.

Structure 2018;26(1):28-39.e2.

Pubmed ID: 29225075

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