THE DROSOPHILA DON-JUAN (DJ) GENE ENCODES A NOVEL SPERM-SPECIFIC PROTEIN-COMPONENT CHARACTERIZED BY AN UNUSUAL DOMAIN OF A REPETITIVE AMINO-ACID MOTIF

We identified and characterized the non juan gene (dj) of Drosophila m elanogaster. The don juan gene codes for a sperm specific protein comp onent with an unusual repetitive six amino acid motif (DPCKKK) in the carboxy-terminal part of the protein. The expression of Don Juan is li mited to male germ cells where transcription of the dj gene is initiat ed during meiotic prophase. But Western blot experiments indicate that DJ protein occurs just postmeiotically. Examination of transgenic fli es bearing a dj-promoter-lacZ reporter construct revealed lacZ mRNA di stribution resembling the expression pattern of the endogenous dj mRNA in the adult testes, whereas beta-galactosidase expression is exclusi vely present in postmeiotic germ cells. Thus, these observations stron gly suggest that dj transcripts are under translational repression unt il spermiogenesis. To study the function and subcellular distribution of DJ in spermiogenesis we expressed a chimaeric dj-GFP fusion gene in the male germline exhibiting strong GFP fluorescence in the live test es, where only elongated spermatids are decorated. With regard to the characteristic expression pattern of DJ protein and its conspicuous re peat units possible functional roles are discussed. (C) 1997 Elsevier Science Ireland Ltd.