Cloning of the barramundi growth hormone-encoding gene: a comparative analysis of higher and lower vertebrate GH genes.

In this work the growth hormone-encoding gene (GH) from the fish barramundi (Lates calcarifer) was characterized by nucleotide (nt) sequence analysis and comparative studies on higher and lower vertebrate GH were performed. The barramundi GH contains six exons and five introns. A putative transcription start point 21 nt downstream from a potential TATAAA box was determined, with a modified primary transcript size of 1615 nt predicted. cis-Acting elements potentially important for transcriptional regulation at the basal, hormone-responsive and pituitary gland-specific levels were identified. Several microsatellite and minisatellite repetitive sequences were shown to be present within noncoding portions of this gene. Repeat sequences similar to the deca- and undeca-minisatellites of the barramundi GH were observed in the corresponding introns of the tilapia, but not other teleost GH. Comparative studies on the Osteichthyes, Mammalia and Aves vertebrate class GH promoters suggested that the TATAAA box was the only conserved region between these sequences. Conserved sequences, however, were identified within the GH promoters of different species from the Osteichthyes or Mammalia classes. The Osteichthyes A + T-rich sequence (consensus GATRMATYWAAWCA, where R = A or G; M = A or C, Y = C or T and W = A or T) is the only conserved region identified between teleost GH promoters, and is most likely involved in the pituitary gland-specific expression of these genes.