title: ATF4-dependent oxidative induction of the DNA repair enzyme Ape1 counteracts arsenite cytotoxicity and suppresses arsenite-mediated mutagenesis.
abstract: Arsenite is a human carcinogen causing skin, bladder, and lung tumors, but the cellular mechanisms underlying these effects remain unclear. We investigated expression of the essential base excision DNA repair enzyme apurinic endonuclease 1 (Ape1) in response to sodium arsenite. In mouse 10T(1/2) fibroblasts, Ape1 induction in response to arsenite occurred about equally at the mRNA, protein, and enzyme activity levels. Analysis of the APE1 promoter region revealed an AP-1/CREB binding site essential for arsenite-induced transcriptional activation in both mouse and human cells. Electrophoretic mobility shift assays indicated that an ATF4/c-Jun heterodimer was the responsible transcription factor. RNA interference targeting c-Jun or ATF4 eliminated arsenite-induced APE1 transcription. Suppression of Ape1 or ATF4 sensitized both mouse fibroblasts (10T(1/2)) and human lymphoblastoid cells (TK6) to arsenite cytotoxicity. Expression of Ape1 from a transgene did not efficiently restore arsenite resistance in ATF4-depleted cells but did offset initial accumulation of abasic DNA damage following arsenite treatment. Mutagenesis by arsenite (at the TK and HPRT loci in TK6 cells) was observed only for ATF4-depleted cells, which was strongly offset by Ape1 expression from a transgene. Therefore, the ATF4-mediated up-regulation of Ape1 and other genes plays a key role against arsenite-mediated toxicity and mutagenesis.
authors.affiliation: Department of Genetics and Complex Diseases, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA.
authors.forename: Hua
authors.initials: H
authors.lastname: Fung
authors.forename: Pingfang
authors.initials: P
authors.lastname: Liu
authors.forename: Bruce
authors.initials: B
authors.lastname: Demple
mesh_terms: D051701:Activating Transcription Factor 4 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D018053:Arsenites / Q000633:toxicity*; D016923:Cell Death / Q000187:drug effects; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects*; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000096:biosynthesis* / Q000235:genetics; D004790:Enzyme Induction / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D051379:Mice; D016296:Mutagenesis / Q000187:drug effects*; D009154:Mutation / Q000235:genetics; D041681:NIH 3T3 Cells; D018384:Oxidative Stress / Q000187:drug effects*; D011485:Protein Binding / Q000187:drug effects; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D020218:Response Elements; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D018053:Arsenites; D016755:Proto-Oncogene Proteins c-jun; D051701:Activating Transcription Factor 4; C085108:APEX1 protein, human; C486216:Apex1 protein, mouse; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase