Regulation of genetic activity by thyroid hormones. II. Specificity of interaction of cytoplasmic thyroxine receptor isolated from human embryonal fibroblasts and HeLa cells with DNA

: The work concerns a new approach to evaluating the receptor and hormone-receptor complex specific interaction with DNA and revealing the cause of the absence of the hormone-receptor complex acceptation with HeLa cell chromosomes. It has been shown that hormone-receptor complexing should precede specific interaction with DNA. The purified receptor-thyroxin complex is saturatable and specifically competes with Hae III restrictase, protecting specific sites of DNA recognition from this enzyme. Specificity of the hormone-receptor complex interaction with DNA depends on the sequences surrounding Hae III restriction site. The HeLa cell hormone-receptor complex does not interact with the recognition site for the normal hormone-receptor complex.