Human Nuclear Thyroid Hormone Receptors

Abstract

Nuclear thyroid hormone receptors are acidic, non–histone, chromatin associated proteins (1) with molecular weights of 47,000 – 57,000 (2,3) and bind T3 with high affinity in the presence of sulfhydryl groups (4). It is generally believed that nuclear receptors mediate biological responses after binding thyroid hormone and induce activation of specific gene expression. Although nuclear thyroid hormone receptors exist in human tissues (5,6), most studies have been performed on rat tissues, including liver, kidney, and cultured pituitary cells. To further study nuclear thyroid hormone receptors in human tissues, we developed an improved isolation method for nuclei of cultured human hepatoma cells (Hep G2) and cultured human fibroblasts. The characteristics of nuclear receptors were compared in these cell lines.