The long term goal of the project is to understand at the molecular level how the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces aryl hydrocarbon hydroxylase (AHH) activity in mammalian cells. The studies pertain to the mechanism of dioxin action, the control of cytochrome P1-450 gene expression, and the regulation of transcription of mammalian genes. The specific aims are to analyze the mechanism of superinduction of AHH activity in mouse hepatoma cells and to analyze the regulation of other, non-cytochrome P1-450 genes under transcriptional control by TCDD. The experiments involve the use of molecular biological techniques for constructing recombinant DNA molecules, biochemical and genetic methods for analyzing the structure and function of these molecules, and the use of these molecules to study the control of gene expression in wild type and variant mouse hepatoma cells.