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.