cDNA cloning of two closely related forms of human germ cell nuclear factor (GCNF)

Germ cell nuclear factor (GCNF) was initially described in the mouse as a germ cell-specific orphan member of the nuclear receptor superfamily. Two full-length cDNAs encoding variants of the human germ cell nuclear factor (GCNF) differing by only one amino acid residue have now been isolated from a human testis cDNA library and characterised. The encoded proteins show 98.3% and 82.7% amino acid identity with mouse and Xenopus GCNF, respectively. Northern blot hybridisation revealed the expression of an 8 kb human GCNF mRNA exclusively in the testis. The alignment of the GCNF protein sequence with other members of the nuclear hormone receptor family suggests an unusual structural organisation of the C-terminal portion of the putative ligand-binding domain.