A SPLICING ENHANCER COMPLEX CONTROLS ALTERNATIVE SPLICING OF DOUBLESEX PREMESSENGER RNA

Female-specific splicing of Drosophila doublesex (dsx) pre-mRNA is reg ulated by the products of the transformer (tra) and transformer 2 (tra 2) genes. In this paper we show that Tra and Tra2 act by recruiting ge neral splicing factors to a regulatory element located downstream of a female-specific 3' splice site. Remarkably, Tra, Tra2, and members of the serine/arginine-rich (SR) family of general splicing factors are sufficient to commit dsx pre-mRNA to female-specific splicing, and ind ividual SR proteins differ significantly in their ability to participa te in commitment complex formation. Characterization of the proteins a ssociated with affinity purified complex formed on dsx pre-mRNA reveal s the presence of Tra, Tra2, SR proteins, and additional unidentified components. We conclude that Tra, Tra2, and SR proteins are essential components of a splicing enhancer complex.