[Role of trace elements on metallothionein gene expression].

Metallothionein (MT) is low-molecular-weight metal binding proteins with a high cysteine content, which provide the protection against metal toxicity and the regulation of essential trace elements such as zinc and copper. MT is inducible proteins by various metals, hormones, cytokines, and endogenous and exogenous agents. Human MT genes locate on chromosome 16, and mainly three isoforms of MT (MT-I, MT-II, MT-III) have been identified. MT genes expression is controlled mainly at the transcriptional level, and is regulated by the interaction between cis-acting elements (MRE, GRE, IRE) and trans-acting factors (MTF-1, ZRF, MRE-BF-1 and 2, MREBP). Regulation of MT genes by metals may be mediated by MTF-1 interacting with MREs and zinc functions to release MTF-1 from an inhibitor (MTI).