A Novel Thyroid Hormone Receptor Encoded by a cDNA Clone from a Human Testis Library

Abstract

The c- erb A gene belongs to a multigene family that encodes transcriptional regulatory proteins including the v- erb A oncogene product, steroid hormone receptors, and the vitamin D3 receptor. A v- erb A DNA probe encoding the DNA-binding region of the v- erb A protein was used to screen a human complementary DNA testis library. One of the clones isolated, erb A-T-1, was found to encode a 490-amino acid protein ( erb A-T). The erb A-T polypeptide shows high homology with the proteins encoded by both the chicken c- erb A and the human c- erb A-β genes but is most closely related to the chicken gene. The chicken c- erb A and the human c- erb A-β genes encode high-affinity receptors for thyroid hormone, and here it is shown that the erb A-T protein binds specifically to 3,5,3 ′-triiodo-L-thyronine with a dissociation constant of 3.8 ± 0.2 × 10 -10 M . These data imply that more than one thyroid hormone receptor exists in humans and that these receptors might have different tissue- and gene-activating specificities.

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Affiliated Institutions

• National Foundation for Cancer Research US
• Discovery Institute US
• Sanford Burnham Prebys Medical Discovery Institute US
• Cancer Research Center US

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