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 barra mundi (Lates calcarifer) was characterized by nucleotide (nt) sequence analysis and comparative studies on higher and lower vertebrate GH we re 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 trans criptional regulation at the basal, hormone-responsive and pituitary g land-specific levels were identified. Several microsatellite and minis atellite repetitive sequences were shown to be present within noncodin g portions of this gene. Repeat sequences similar to the deca- and und eca-minisatellites of the barramundi GH were observed in the correspon ding introns of the tilapia, but not other teleost GH. Comparative stu dies on the Osteichthyes, Mammalia and Aves vertebrate class GH promot ers suggested that the TATAAA box was the only conserved region betwee n these sequences. Conserved sequences, however, were identified withi n the GH promoters of different species from the Osteichthyes or Mamma lia classes. The Osteichthyes A + T-rich sequence (consensus GATRMATYW AAWCA, where R=A or G; M=A or C, Y=C or T and W=A or T) is the only co nserved region identified between teleost GH promoters, and is most li kely involved in the pituitary gland-specific expression of these gene s.