title: Novel role of antioxidant-1 (Atox1) as a copper-dependent transcription factor involved in cell proliferation.
abstract: Copper plays a fundamental role in regulating cell growth. Many types of human cancer tissues have higher copper levels than normal tissues. Copper can also induce gene expression. However, transcription factors that mediate copper-induced cell proliferation have not been identified in mammals. Here we show that antioxidant-1 (Atox1), previously appreciated as a copper chaperone, represents a novel copper-dependent transcription factor that mediates copper-induced cell proliferation. Stimulation of mouse embryonic fibroblasts (MEFs) with copper markedly increased cell proliferation, cyclin D1 expression, and entry into S phase, which were completely abolished in Atox1(-/-) MEFs. Promoter analysis and EMSA revealed that copper stimulates the Atox1 binding to a previously undescribed cis element in the cyclin D1 promoter. The ChIP assay confirms that copper stimulates Atox1 binding to the DNA in vivo. Transfection of Atox1 fused to the DNA-binding domain of Gal4 demonstrated a copper-dependent transactivation in various cell types, including endothelial and cancer cells. Furthermore, Atox1 translocated to the nucleus in response to copper through its highly conserved C-terminal KKTGK motif and N-terminal copper-binding sites. Finally, the functional role of nuclear Atox1 is demonstrated by the observation that re-expression of nuclear-targeted Atox1 in Atox1(-/-) MEFs rescued the defective copper-induced cell proliferation. Thus, Atox1 functions as a novel transcription factor that, when activated by copper, undergoes nuclear translocation, DNA binding, and transactivation, thereby contributing to cell proliferation.
authors.affiliation: Division of Cardiology, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Itoh
authors.forename: Ha Won
authors.initials: HW
authors.lastname: Kim
authors.forename: Osamu
authors.initials: O
authors.lastname: Nakagawa
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Ozumi
authors.forename: Susan M
authors.initials: SM
authors.lastname: Lessner
authors.forename: Hiroki
authors.initials: H
authors.lastname: Aoki
authors.forename: Kamran
authors.initials: K
authors.lastname: Akram
authors.forename: Ronald D
authors.initials: RD
authors.lastname: McKinney
authors.forename: Masuko
authors.initials: M
authors.lastname: Ushio-Fukai
authors.forename: Tohru
authors.initials: T
authors.lastname: Fukai
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000235:genetics; D020816:Amino Acid Motifs / Q000235:genetics; D000818:Animals; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D003300:Copper / Q000378:metabolism / Q000494:pharmacology*; D000079922:Copper Transport Proteins; D056741:Cyclin D; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D004622:Embryo, Mammalian / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D006801:Humans; D056511:Metallochaperones; D051379:Mice; D018345:Mice, Knockout; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D016196:S Phase / Q000187:drug effects* / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C474500:ATOX1 protein, human; C499247:Atox1 protein, mouse; D027682:Cation Transport Proteins; D000079922:Copper Transport Proteins; D056741:Cyclin D; D016213:Cyclins; D056511:Metallochaperones; D018832:Molecular Chaperones; D014157:Transcription Factors; D003300:Copper