Characterization of the DNA‐binding properties of the receptor for 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin

The DNA‐binding properties of the receptor for 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) were investigated using chromatography on DNA‐cellulose columns. A maximal binding of about 40% of the total receptor complex to DNA‐cellulose was observed. In order to interact with DNA, the receptor must first bind TCDD. A heat‐activation step followed by gel permeation chromatography using Sephadex G‐25 increased the binding of the cytosolic receptor to DNA. The DNA‐binding ability of the receptor was almost lost following mild proteolysis using trypsin or α‐chymotrypsin, although these treatments did not reduce its ligand binding capacity and had no apparent effect on its size. Furthermore, pre‐treatment of the DNA‐cellulose column with an intercalating drug, ethidium bromide, resulted in inhibition of the binding of the TCDd‐receptor complex to DNA, indicating that not only electrostatic interactions but also the configuration of DNA are of importance in receptor‐DNA interactions.