Alternative splicing of the sex determination gene transformer-2 is sex-specific in the germ line but not in the soma

The transformer-2 (tra-2) gene of Drosophila melanogaster plays essential roles in both sexual differentiation in the female soma and spermatogenesis in the male germ line. In the female soma, tra-2 is known to act with other genes in the sex determination regulatory cascade to control the sex-specific alternative splicing of transcripts from the doublesex gene. Here, we determine whether or not any sex-specific tra-2 products are expressed that may account for either of these sex-specific activities. Sequence analysis of the tra-2 gene and 10 tra-2 cDNA clones coupled with nuclease protection analysis reveals a variety of alternatively spliced tra-2 mRNAs that each encode one of four distinct but overlapping polypeptides. Three of the encoded polypeptides contain both a ribonucleoprotein consensus sequence and arginine/serine-rich regions, suggesting a direct role for these products in RNA splicing. We show that although two transcripts are expressed male specifically in the germ line, the tra-2 transcripts expressed in the soma are not sex-specific. The translation of products from a tra-2-lacZ fusion gene in both sexes suggests that the female-specific functioning of tra-2 in somatic tissues is not attributable to a translational mechanism. We suggest that tra-2 activity in somatic tissues is regulated through a post-translational sex-specific interaction with the product of the tra gene rather than through the expression of a female-specific tra-2 polypeptide.