THE AUSTRALIAN BRUSHTAIL POSSUM (TRICHOSURUS-VULPECULA) GONADOTROPIN ALPHA-SUBUNIT - ANALYSIS OF CDNA SEQUENCE AND PATTERN OF EXPRESSION

A cDNA sequence from the gonadotrophin alpha-subunit mRNA of Australia n brushtail possum (Trichosurus vulpecula) has been determined and ana lysed. Comparison with seven eutherian mammalian gonadotrophin ar-subu nit gene sequences revealed an average of 82.6% homology between the c oding region nucleotide sequences and 88.8% identity between the predi cted amino acid sequences. The predicted possum gonadotrophin alpha-su bunit protein has ten evolutionarily conserved cysteine residues, two potential N-linked glycosylation sites and a putative enzyme recogniti on sequence which it has been suggested is required for sulphation of carbohydrate moieties. Comparison of the possum gonadotrophin alpha-su bunit 3' untranslated region (UTR) sequence with the 3' UTRs of euther ian alpha-subunit transcripts revealed sequence homology. In particula r, an 18 nucleotide imperfect palindromic sequence present in the poss um 3' UTR, with the potential to form a hairpin loop, was found to be evolutionarily conserved and present in five out of seven eutherian al pha-subunit 3' UTR sequences. In situ hybridization localized the tran scripts to a sub-population of anterior pituitary cells presumed to be gonadotrophs and thyrotrophs. In summary, these results indicate cons iderable conservation of the structure and function of the gonadotroph in alpha-subunit protein since the divergence of the marsupial and eut herian mammalian lineages.