Metal-specific posttranscriptional control of human metallothionein genes.

During the initial 4 h of treatment, copper and zinc similarly activated the rates of transcription and mRNA accumulation from the two human metallothionein (MT) genes, viz., MTI-G and MTII-A, in the hepatoblastoma cell line HepG2. The levels of copper-induced MT mRNAs remained at a plateau for up to 15 h. In contrast, the levels of zinc-induced MT mRNAs gradually declined after about 4 h, despite substantial transcription. The decrease in the zinc-induced MT mRNA half-life is probably due to a posttranscriptional event(s).