title: Oncogenic H-Ras enhances DNA repair through the Ras/phosphatidylinositol 3-kinase/Rac1 pathway in NIH3T3 cells. Evidence for association with reactive oxygen species.
abstract: This study investigated the role of oncogenic H-Ras in DNA repair capacity in NIH3T3 cells. Expression of dominant-positive H-Ras (V12-H-Ras) enhanced the host cell reactivation of luciferase activity from UV-irradiated and cisplatin-treated plasmids and also increased the unscheduled DNA synthesis following cisplatin or UV treatment of cells. This observed enhancement of DNA repair capacity was inhibited by transient transfection with dominant-negative H-Ras (N17-H-Ras) or Rac1 (N17-Rac1) plasmids. Moreover, stable transfection of dominant-positive Rac1 (V12-Rac1) further enhanced DNA repair capacity. Because reactive oxygen species (ROS) are known to be a downstream effector of oncogenic Ras, we examined the role of ROS in DNA repair capacity. We found that ROS production by V12-H-Ras expression was mediated by the Ras/phosphatidylinositol 3-kinase (PI3K)/Rac1/NADPH oxidase-dependent pathway and that pretreatment of V12-H-Ras-transformed cells with an antioxidant (N-acetylcysteine) and an NADPH oxidase inhibitor (diphenyleneiodonium) decreased DNA repair capacity. Similarly, treatment with PI3K inhibitors (wortmannin and LY294002) inhibited the ability of oncogenic H-Ras to enhance DNA repair capacity. Furthermore, inhibition of the Ras/PI3K/Rac1/NADPH oxidase pathway resulted in increased sensitivity to cisplatin and UV in V12-H-Ras-expressing NIH3T3 cells. Taken together, these results provide evidence that oncogenic H-Ras activates DNA repair capacity through the Ras/PI3K/Rac1/NADPH oxidase-dependent pathway and that increased ROS production via this signaling pathway is required for enhancement of the DNA repair capacity induced by oncogenic H-Ras.
authors.affiliation: Department of Pharmacology, School of Medicine, the Research Center for Proteineous Materials, Chosun University, 375 Seosuk-dong, Kwangju 501-759, Korea. hjyou@mail.chosun.ac.kr
authors.forename: Hyun-Ju
authors.initials: HJ
authors.lastname: Cho
authors.forename: Hye Gwang
authors.initials: HG
authors.lastname: Jeong
authors.forename: Jung-Sup
authors.initials: JS
authors.lastname: Lee
authors.forename: Eun-Rhan
authors.initials: ER
authors.lastname: Woo
authors.forename: Jin-Won
authors.initials: JW
authors.lastname: Hyun
authors.forename: Myung-Hee
authors.initials: MH
authors.lastname: Chung
authors.forename: Ho Jin
authors.initials: HJ
authors.lastname: You
mesh_terms: D016475:3T3 Cells; D000111:Acetylcysteine / Q000494:pharmacology; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival; D002867:Chromones / Q000494:pharmacology; D002945:Cisplatin / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis; D004260:DNA Repair; D004791:Enzyme Inhibitors / Q000494:pharmacology; D011905:Genes, ras / Q000235:genetics*; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D017382:Reactive Oxygen Species; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection; D014466:Ultraviolet Rays; D000077191:Wortmannin; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D000730:Androstadienes; D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D017382:Reactive Oxygen Species; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D004247:DNA; D008156:Luciferases; D019869:Phosphatidylinositol 3-Kinases; D020830:rac1 GTP-Binding Protein; D018631:ras Proteins; D002945:Cisplatin; D000111:Acetylcysteine; D000077191:Wortmannin