title: CBP-93872 inhibits NBS1-mediated ATR activation, abrogating maintenance of the DNA double-strand break-specific G2 checkpoint.
abstract: CBP-93872 was previously identified as a G2 checkpoint inhibitor using a cell-based high-throughput screening system. However, its molecular actions as well as cellular targets are largely unknown. Here, we uncovered the molecular mechanisms underlying abrogation of the G2 checkpoint by CBP-93872. CBP-93872 specifically abrogates the DNA double-stranded break (DSB)-induced G2 checkpoint through inhibiting maintenance but not initiation of G2 arrest because of specific inhibition of DSB-dependent ATR activation. Hence, ATR-dependent phosphorylation of Nbs1 and replication protein A 2 upon DSB was strongly suppressed in the presence of CBP-93872. CBP-93872 did not seem to inhibit DNA-end resection, but did inhibit Nbs1-dependent and ssDNA-induced ATR activation in vitro in a dose-dependent manner. Taken together, our results suggest that CBP-93872 is an inhibitor of maintenance of the DSB-specific G2 checkpoint and thus might be a strong candidate as the basis for a drug that specifically sensitizes p53-mutated cancer cells to DSB-inducing DNA damage therapy.
authors.affiliation: Authors' Affiliations: Departments of Cell Biology and Gastroenterological Surgery, Graduate School of Medical Sciences, Nagoya City University, Mizuho-cho, Mizuho-ku, Nagoya; and.
authors.forename: Takahisa
authors.initials: T
authors.lastname: Hirokawa
authors.affiliation: Department of Cellular and Molecular Biology, Hiroshima University, Hiroshima, Japan.
authors.forename: Bunsyo
authors.initials: B
authors.lastname: Shiotani
authors.affiliation: Authors' Affiliations: Departments of Cell Biology and.
authors.forename: Midori
authors.initials: M
authors.lastname: Shimada
authors.affiliation: Authors' Affiliations: Departments of Cell Biology and.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Murata
authors.affiliation: Authors' Affiliations: Departments of Cell Biology and.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Johmura
authors.affiliation: Authors' Affiliations: Departments of Cell Biology and.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Haruta
authors.affiliation: Department of Cellular and Molecular Biology, Hiroshima University, Hiroshima, Japan.
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Tahara
authors.affiliation: Gastroenterological Surgery, Graduate School of Medical Sciences, Nagoya City University, Mizuho-cho, Mizuho-ku, Nagoya; and.
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Takeyama
authors.affiliation: Authors' Affiliations: Departments of Cell Biology and mkt-naka@med.nagoya-cu.ac.jp.
authors.forename: Makoto
authors.initials: M
authors.lastname: Nakanishi
mesh_terms: D000814:Aniline Compounds / Q000494:pharmacology*; D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects*; D006801:Humans; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011412:Propanolamines / Q000494:pharmacology*; D011485:Protein Binding
chemical_list: D000814:Aniline Compounds; C000591842:CBP-93872; D018797:Cell Cycle Proteins; C112156:NBN protein, human; D009687:Nuclear Proteins; D011412:Propanolamines; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins