title: Differential effect of schisandrin B stereoisomers on ATR-mediated DNA damage checkpoint signaling.
abstract: We have previously reported that schisandrin B (SchB) is a specific inhibitor of ATR (ataxia telangiectasia and Rad-3-related) protein kinase. Since SchB consists of a mixture of its diastereomers gomisin N (GN) and γ-schisandrin (γ-Sch), the inhibitory action of SchB might result from a stereospecific interaction between one of the stereoisomers of SchB and ATR. Therefore, we investigated the effect of GN and γ-Sch on UV (UVC at 254 nm)-induced activation of DNA damage checkpoint signaling in A549 cells. UV-induced cell death (25 - 75 J/m(2)) was amplified by the presence of the diastereomers, especially GN. At the same time, GN, but not γ-Sch, inhibited the phosphorylation of checkpoint proteins such as p53, structural maintenance of chromosomes 1, and checkpoint kinase 1 in UV-irradiated cells. Moreover, GN inhibited the G2/M checkpoint during UV-induced DNA damage. The in vitro kinase activity of immunoaffinity-purified ATR was dose-dependently inhibited by GN (IC50: 7.28 μM) but not by γ-Sch. These results indicate that GN is the active component of SchB and suggest that GN inhibits the DNA damage checkpoint signaling by stereospecifically interacting with ATR.
authors.affiliation: Department of Functional and Analytical Food Sciences, Faculty of Applied Life Sciences, Niigata University of Pharmacy & Applied Life Sciences, Niigata, Japan.
authors.forename: Naoto
authors.initials: N
authors.lastname: Tatewaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nishida
authors.forename: Masaaki
authors.initials: M
authors.lastname: Yoshida
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Ando
authors.forename: Seizo
authors.initials: S
authors.lastname: Kondo
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Sakamaki
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Konishi
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D034242:Cyclooctanes / Q000737:chemistry / Q000494:pharmacology; D004249:DNA Damage; D004305:Dose-Response Relationship, Drug; D018816:Genes, cdc / Q000187:drug effects* / Q000235:genetics; D006801:Humans; D017705:Lignans / Q000737:chemistry / Q000494:pharmacology*; D011083:Polycyclic Compounds / Q000737:chemistry / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D034242:Cyclooctanes; D017705:Lignans; D011083:Polycyclic Compounds; C015499:schizandrin B; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins