title: Chk1 activation requires Rad9 S/TQ-site phosphorylation to promote association with C-terminal BRCT domains of Rad4TOPBP1.
abstract: To gain insight into the function and organization of proteins assembled on the DNA in response to genotoxic insult we investigated the phosphorylation of the Schizosaccharomyces pombe PCNA-like checkpoint protein Rad9. C-terminal T412/S423 phosphorylation of Rad9 by Rad3(ATR) occurs in S phase without replication stress. Rad3(ATR) and Tel1(ATM) phosphorylate these same residues, plus additional ones, in response to DNA damage. In S phase and after damage, only Rad9 phosphorylated on T412/S423, but not unphosphorylated Rad9, associates with a two-BRCT-domain region of the essential Rad4(TOPBP1) protein. Rad9-Rad4(TOPBP1) interaction is required to activate the Chk1 damage checkpoint but not the Cds1 replication checkpoint. When the Rad9-T412/S423 are phosphorylated, Rad4(TOPBP1) coprecipitates with Rad3(ATR), suggesting that phosphorylation coordinates formation of an active checkpoint complex.
authors.affiliation: Genome Damage and Stability Centre, University of Sussex, Brighton, BN1 9RQ, UK.
authors.forename: Kanji
authors.initials: K
authors.lastname: Furuya
authors.forename: Marius
authors.initials: M
authors.lastname: Poitelea
authors.forename: Liandi
authors.initials: L
authors.lastname: Guo
authors.forename: Thomas
authors.initials: T
authors.lastname: Caspari
authors.forename: Antony M
authors.initials: AM
authors.lastname: Carr
mesh_terms: D001665:Binding Sites / Q000235:genetics; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000071877:Checkpoint Kinase 1; D064447:Checkpoint Kinase 2; D004249:DNA Damage; D004261:DNA Replication; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D008954:Models, Biological; D009154:Mutation; D010766:Phosphorylation; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016196:S Phase; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011503:Transglutaminases / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; C082463:RAD4 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; C069930:rad9 protein; D011503:Transglutaminases; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; D000071877:Checkpoint Kinase 1; C000605873:Chk1 protein, S pombe; C456840:rad3 protein, S pombe