title: Association of Rad9 with double-strand breaks through a Mec1-dependent mechanism.
abstract: Rad9 is required for the activation of DNA damage checkpoint pathways in budding yeast. Rad9 is phosphorylated after DNA damage in a Mec1- and Tel1-dependent manner and subsequently interacts with Rad53. This Rad9-Rad53 interaction has been suggested to trigger the activation and phosphorylation of Rad53. Here we show that Mec1 controls the Rad9 accumulation at double-strand breaks (DSBs). Rad9 was phosphorylated after DSB induction and associated with DSBs. However, its phosphorylation and association with DSBs were significantly decreased in cells carrying a mec1Delta or kinase-negative mec1 mutation. Mec1 phosphorylated the S/TQ motifs of Rad9 in vitro, the same motifs that are phosphorylated after DNA damage in vivo. In addition, multiple mutations in the Rad9 S/TQ motifs resulted in its defective association with DSBs. Phosphorylation of Rad9 was partially defective in cells carrying a weak mec1 allele (mec1-81), whereas its association with DSBs occurred efficiently in the mec1-81 mutants, as found in wild-type cells. However, the Rad9-Rad53 interaction after DSB induction was significantly decreased in mec1-81 mutants, as it was in mec1Delta mutants. Deletion mutation in RAD53 did not affect the association of Rad9 with DSBs. Our results suggest that Mec1 promotes association of Rad9 with sites of DNA damage, thereby leading to full phosphorylation of Rad9 and its interaction with Rad53.
authors.affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-0814, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Naiki
authors.forename: Tatsushi
authors.initials: T
authors.lastname: Wakayama
authors.forename: Daisuke
authors.initials: D
authors.lastname: Nakada
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Katsunori
authors.initials: K
authors.lastname: Sugimoto
mesh_terms: D020816:Amino Acid Motifs; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000378:metabolism*; D064447:Checkpoint Kinase 2; D004249:DNA Damage; D004260:DNA Repair; D004277:DNA, Single-Stranded / Q000378:metabolism; D018816:Genes, cdc; D047908:Intracellular Signaling Peptides and Proteins; D009154:Mutation; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D004277:DNA, Single-Stranded; D047908:Intracellular Signaling Peptides and Proteins; D029701:Saccharomyces cerevisiae Proteins; C069930:rad9 protein; D064447:Checkpoint Kinase 2; C088937:MEC1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; C067022:RAD53 protein, S cerevisiae