Metallothionein-IIA gene transcription in cisplatin-resistant cells and its metal-signalling mechanism by Cu(II) ion

Abstract

Increased metallothionein (MT)-IIA transcription is found in some cells with acquired resistance to cisplatin (CDDP). It is also known that mammalian MT is induced by copper. MT induction by TPA (12-O-tetradecanoyl phorbol-13-acetate) and TNFα (tumor necrosis factor α has been demonstrated. In previous study, we found Cu(II) ion dependency on binding of the nuclear protein of HeLa cells stimulated with TPA or TNFα to the metal responsive elements (MREs) sequences in the MT-IIA promoter gene, which was investigated by the gel shift assay using the plasmid pKB8 constructed the human MT-IIA promoter gene in pUC19. Therefore, it was suggested that the nuclear protein bound specificically to the MT-IIA promoter region in the presence of Cu(II) ion contributes to CDDP resistance by regulation of MT-IIA gene expression. In this study Cu(II) ion dependency on binding of the nuclear protein from the CDDP-resistant cells to the DNA fragments containing MREs in the MT-IIA promoter gene was examined in connection with observation of the MT-IIA gene expression (mRNAs) in CDDP-resistant cells.