title: Inhibition of AP-1 binding and transcription by gold and selenium involving conserved cysteine residues in Jun and Fos.
abstract: Gold(I) salts and selenite, which have diverse therapeutic and biological effects, are noted for their reactivity with thiols. Since the binding of Jun-Jun and Jun-Fos dimers to the AP-1 DNA binding site is regulated in vitro by a redox process involving conserved cysteine residues, we hypothesized that some of the biological actions of gold and selenium are mediated via these residues. In electrophoretic mobility-shift analyses, AP-1 DNA binding was inhibited by gold(I) thiolates and selenite, with 50% inhibition occurring at approximately 5 microM and 1 microM, respectively. Thiomalic acid had no effect in the absence of gold(I), and other metal ions inhibited at higher concentrations, in a rank order correlating with their thiol binding affinities. Cysteine-to-serine mutants demonstrated that these effects of gold(I) and selenite require Cys272 and Cys154 in the DNA-binding domains of Jun and Fos, respectively. Gold(I) thiolates and selenite did not inhibit nonspecific protein binding to the AP-1 site and were at least an order of magnitude less potent as inhibitors of sequence-specific binding to the AP-2, TFIID, or NF1 sites compared with the AP-1 site. In addition, 10 microM gold(I) or 10 microM selenite inhibited expression of an AP-1-dependent reporter gene, but not an AP-2-dependent reporter gene. These data suggest a mechanism regulating transcription factor activity by inorganic ions which may contribute to the known antiarthritic action of gold and cancer chemoprevention by selenium.
authors.affiliation: Cancer Biology Division, Garvan Institute of Medical Research, Sydney, New South Wales, Australia.
authors.forename: M L
authors.initials: ML
authors.lastname: Handel
authors.forename: C K
authors.initials: CK
authors.lastname: Watts
authors.forename: A
authors.initials: A
authors.lastname: deFazio
authors.forename: R O
authors.initials: RO
authors.lastname: Day
authors.forename: R L
authors.initials: RL
authors.lastname: Sutherland
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D001943:Breast Neoplasms; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis / Q000378:metabolism; D017124:Conserved Sequence; D003545:Cysteine; D004305:Dose-Response Relationship, Drug; D006046:Gold / Q000494:pharmacology*; D006052:Gold Sodium Thiomalate / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D016760:Proto-Oncogene Proteins c-fos / Q000737:chemistry / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000737:chemistry / Q000378:metabolism*; D018038:Sodium Selenite / Q000494:pharmacology*; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D006052:Gold Sodium Thiomalate; D006046:Gold; D015500:Chloramphenicol O-Acetyltransferase; D018038:Sodium Selenite; D003545:Cysteine