title: C-terminal deletion mutant of MRE-binding transcription factor-1 inhibits MRE-driven gene expression.
abstract: Heavy metal-induced transcriptional activation of the genes coding for metallothionein (MT) is mediated by a cis-acting DNA element, the metal-responsive element (MRE). MRE-binding transcription factor-1 (MTF-1) is a highly conserved heavy metal-induced transcriptional activator. MTF-1 also activates transcription in response to oxidative stress and regulates the expression of several cytoprotective factor genes, including MT, gamma-glutamylcysteine synthetase, and Cu/Zn-superoxide dismutase. It is thus thought that MTF-1 plays a role in cellular stress response. The physiological role of MTF-1 remains unclear because of the lack of MTF-1-specific activators and/or inhibitors. To obtain an MTF-1-specific inhibitor, we constructed an MTFDeltaC (amino acids 1-317), a C-terminal deletion mutant of MTF-1. MTFDeltaC could bind MRE and competed with MTF-1 for MTF-MRE complex formation. Transient expression of MTFDeltaC in HepG2 cells reduced MRE-driven gene expression, demonstrating that MTFDeltaC is dominant to MTF-1. HepG2 cells stably expressing MTFDeltaC showed increased susceptibility to the cytotoxic effects of tert-butyl hydroperoxide (tBH). Furthermore, we constructed Ad5MTFDeltaC, a recombinant adenovirus that expresses MTFDeltaC. Infection with the virus induced MTFDeltaC expression and increased susceptibility to the cytotoxic effects of tBH. These results indicate that MTF-1 participates in controlling the cellular redox state.
authors.affiliation: Department of Toxicology, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka 573-0101, Japan. tomoki@pharm.setsunan.ac.jp
authors.forename: Tomoki
authors.initials: T
authors.lastname: Kimura
authors.forename: Norio
authors.initials: N
authors.lastname: Itoh
authors.forename: Tomomichi
authors.initials: T
authors.lastname: Sone
authors.forename: Keiichi
authors.initials: K
authors.lastname: Tanaka
authors.forename: Masakazu
authors.initials: M
authors.lastname: Isobe
mesh_terms: D004268:DNA-Binding Proteins; D024202:Electrophoretic Mobility Shift Assay; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics*; D017930:Genes, Reporter / Q000235:genetics; D006801:Humans; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D020122:tert-Butylhydroperoxide / Q000633:toxicity; D000097809:Transcription Factor MTF-1
chemical_list: D004268:DNA-Binding Proteins; D008668:Metallothionein; D014157:Transcription Factors; D020122:tert-Butylhydroperoxide; D000097809:Transcription Factor MTF-1