Control of gene expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin. Multiple dioxin-responsive domains 5'-ward of the cytochrome P1-450 gene.

In mouse hepatoma cells, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) stimulates cytochrome P1-450 gene transcription via the formation of TCDD-receptor complexes and the accumulation of the complexes in the nucleus. Here, we show that the DNA that flanks the 5'-end of the cytochrome P1-450 gene contains at least two discrete TCDD-responsive domains. Each domain has properties analogous to those of transcriptional enhancers. Each domain requires TCDD-receptor complexes for its function. There is no significant nucleotide sequence homology between the two TCDD-responsive domains.