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Diphosphothreonine-specific interaction between an SQ/TQ cluster and an FHA domain in the Rad53-Dun1 kinase cascade.

Molecular cell | Jun 20, 2008

http://www.ncbi.nlm.nih.gov/pubmed/18570878

Forkhead-associated (FHA) domains recognize phosphothreonines, and SQ/TQ cluster domains (SCDs) contain concentrated phosphorylation sites for ATM/ATR-like DNA-damage-response kinases. The Rad53-SCD1 has dual functions in regulating the activation of the Rad53-Dun1 checkpoint kinase cascade but with unknown molecular mechanisms. Here we present structural, biochemical, and genetic evidence that Dun1-FHA possesses an unprecedented diphosphothreonine-binding specificity. The Dun1-FHA has >100-fold increased affinity for diphosphorylated relative to monophosphorylated Rad53-SCD1 due to the presence of two separate phosphothreonine-binding pockets. In vivo, any single threonine of Rad53-SCD1 is sufficient for Rad53 activation and RAD53-dependent survival of DNA damage, but two adjacent phosphothreonines in the Rad53-SCD1 and two phosphothreonine-binding sites in the Dun1-FHA are necessary for Dun1 activation and DUN1-dependent transcriptional responses to DNA damage. The results uncover a phospho-counting mechanism that regulates the specificity of SCD, and provide mechanistic insight into a role of multisite phosphorylation in DNA-damage signaling.

Pubmed ID: 18570878 RIS Download

Mesh terms: Binding Sites | Cell Cycle Proteins | Checkpoint Kinase 2 | DNA Damage | DNA, Fungal | Enzyme Activation | Kinetics | Ligands | Phosphothreonine | Protein Binding | Protein Kinases | Protein Processing, Post-Translational | Protein-Serine-Threonine Kinases | Saccharomyces cerevisiae | Saccharomyces cerevisiae Proteins | Sensitivity and Specificity

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