REGULATION OF SEX-SPECIFIC SELECTION OF FRUITLESS 5'-SPLICE SITES BY TRANSFORMER AND TRANSFORMER-2

In Drosophila melanogaster, the fruitless (fru) gene controls essentia lly all aspects of male courtship behavior, It does this through sex-s pecific alternative splicing of the fru pre-mRNA, leading to the produ ction of male-specific fru mRNAs capable of expressing male-specific f ru proteins, Sex specific fru splicing involves the choice between alt ernative 5' splice sites, one used exclusively in males and the other used only in females, Here we report that the Drosophila sex determina tion genes transformer (tra) and transformer-2 (tra-2) switch fru spli cing from the male-specific pattern to the female-specific pattern thr ough activation of the female-specific fru 5' splice site, Activation of female-specific fru splicing requires cis-acting tra and tra-2 repe at elements that are part of an exonic splicing enhancer located immed iately upstream of the female-specific fru 5' splice site and are reco gnized by the TRA and TRA-2 proteins in vitro. This fru splicing enhan cer is sufficient to promote the activation by tra and tra-2 of both a 5' splice site and the female-specific doublesex (dsx) 3' splice site , suggesting that the mechanisms of 5' splice site activation and 3' s plice site activation may be similar.