ISOLATION OF A LIVER-SPECIFIC PROMOTER FOR HUMAN GROWTH-HORMONE RECEPTOR GENE

The biological actions of growth hormone (GH) are mediated through the growth hormone receptor (GHR). The GHR gene is expressed in a tissue specific manner and multiple variants (V1 to Vg) of GHR mRNA have been detected in human tissues. To understand the regulation of GHR gene e xpression, a human genomic clone containing the 5'-untranslated region (5'UTR) of the V1, V4, V7 and V8 exons of the GHR was isolated. The 2 kilobase (kb) 5' upstream sequence of the Vf. specific UTR has promot er activity in transient transfection assays of the human hepatoma cel l line, HepG2. The exclusive expression of the V1 variant in adult liv er, and the lack of expression of the other variants in this tissue, s uggests that the V1 5'UTR represents the liver specific 5' noncoding e xon for the human GHR gene. The data are consistent with the first iso lation of a liver specific promoter for human GHR.