amanitins and Ovarian-Neoplasms

ERCC-1 is an essential gene in the nucleotide excision repair pathway, and may be essential for life. However, the mechanism of transcriptional activation and regulation of ERCC-1 gene expression is unclear. We therefore investigated the effect of the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA) on the expression of the ERCC-1 gene in A2780/CP70 human ovarian carcinoma cells. TPA induced a four- to sixfold increase in steady-state ERCC-1 messenger RNA (mRNA) levels that was time- and concentration-dependent. Nuclear run-on experiments demonstrated that the rate of transcription of ERCC-1 was approximately 2.8-fold higher in TPA-treated cells than in the controls. TPA stimulation of A2780/CP70 cells also resulted in a rapid but transient induction of c-jun and c-fos as determined by Northern and Western blot analyses, which peaked about 2 h before the peak in ERCC-1 expression. Electrophoretic mobility shift assays of nuclear extracts from TPA-treated cells revealed an increase in DNA-binding activity specific for the AP-1-like binding site in the 5'-flanking region of ERCC-1. c-Jun and c-Fos proteins were confirmed to be the components of the activated AP-1 complex by supershift analysis. The increase in AP-1 activity occurs immediately before the increase in ERCC-1 transcription. The increase in AP-1 DNA-binding activity and the increase in ERCC-1 mRNA expression were prevented by pretreatment with cycloheximide. These data suggest that AP-1 may contribute to the upregulation of ERCC-1 in response to TPA in human ovarian cancer cells.

Topics: Amanitins; Binding Sites; Carcinogens; Cycloheximide; DNA Repair; DNA-Binding Proteins; Endonucleases; Female; Gene Expression Regulation, Neoplastic; Humans; Neoplasm Proteins; Nucleic Acid Synthesis Inhibitors; Ovarian Neoplasms; Protein Synthesis Inhibitors; Proteins; RNA, Messenger; RNA, Neoplasm; Tetradecanoylphorbol Acetate; Transcription Factor AP-1; Transcription, Genetic; Tumor Cells, Cultured

ERCC-1 is a critical gene within the nucleotide excision repair pathway, and cells without a functional ERCC-1 do not perform cisplatin-DNA adduct repair. We therefore investigated the cisplatin effect on ERCC-1 mRNA expression in vitro. In response to a 1-h cisplatin exposure, A2780/CP70 human ovarian cancer cells showed a 6-fold increase in steady-state level of ERCC-1 mRNA. This rise was attributable to increased transcription as measured by nuclear run-on assays and a 60% increase in ERCC-1 mRNA half-life. The increase in ERCC-1 mRNA was preceded by a 4-5-fold rise in mRNA expressions of c-fos and c-jun, a 14-fold increase in c-Jun protein phosphorylation, and an increase in in vitro nuclear extract binding activity to the AP-1-like site of ERCC-1. These data suggest that the induction of ERCC-1 expression in A2780/CP70 cells exposed to cisplatin results from two major factors: (a) an increase in the expression of transactivating factors that bind the AP-1-like site in the 5'-flanking region of ERCC-1 and (b) an increase in the level of c-Jun phosphorylation that enhances its transactivation property.

Topics: Amanitins; Cisplatin; Cycloheximide; DNA Adducts; DNA-Binding Proteins; Endonucleases; Female; Gene Expression Regulation, Neoplastic; Half-Life; Humans; Ovarian Neoplasms; Protein Binding; Protein Biosynthesis; Proto-Oncogene Proteins c-fos; Proto-Oncogene Proteins c-jun; RNA, Messenger; Transcription Factor AP-1; Up-Regulation