Activation of a heterologous promoter in response to dexamethasone and cadmium by metallothionein gene 5'-flanking DNA.

Human metallothionein-IIA (hMT-IIA) gene expression is regulated by heavy metals and glucocorticoids. When the cloned hMT-IIA gene or its 5'-flanking DNA structure fused to herpes simplex virus thymidine kinase (HSV-TK) structural gene sequences were transferred into TK- Rat 2 fibroblasts, both genes were inducible by Cd++ and/or dexamethasone. Placement of the hMT-IIA gene 5'-flanking region, either intact of deleted in its TATA box and cap site, upstream of the HSV-TK gene promoter rendered the latter both glucocorticoid- and heavy metal-inducible. Thus the structure that mediates both Cd++ and glucocorticoid responsiveness is present in the hMT-IIA gene 5'-flanking DNA, does not require its TATA box or cap site, and can activate a heterologous promoter.