Structure of the chicken growth hormone-encoding gene and its promoter region.

We have cloned the chicken (c) growth hormone (GH)-encoding gene cGH and analyzed its nucleotide sequence including 500 bp of the 5'-flanking region. The cGH gene consists of five exons and four introns as has been observed in the mammalian GH genes. However, the size of the cGH gene is significantly larger than that of analogous mammalian genes, because of its intron size which expands it to 3.5 kb. The transcription start point was determined to be 56 bp upstream from the start codon by the primer-extension analysis. The promoter region of the cGH gene has no overall homology with the corresponding regions of mammalian genes, but contains a short (24 bp) sequence which is highly homologous to the antisense strand sequence of the proximal binding site for a pituitary-specific transcription factor, GHF-1/Pit-1, in the promoter region of the rat GH gene.