ALTERNATIVE SPLICING OF THE DROSOPHILA-MELANOGASTER ROTUNDRACGAP GENE

The rotund (rn) gene in Drosophila melanogaster codes for a RacGTPase- activating protein, RnRacGAP. Cellular studies have shown that RacGAP proteins function as negative regulators of substrate Rac proteins whi ch, in turn, control the localization and polymerization state of acti n within the cell. Previous sequence analysis of sn genomic DNA and in complete cDNA clones suggested that at least two differentially splice d forms of the transcript exist, rnRacGAP(1) and rnRacGAP(2). Using ne sted reverse transcription-polymerase chain reaction (RT-PCR) methods, we have cloned missing exon and intron sequences, and detected differ ences between rnRacGAP(1) and rnRacGAP(2) involving 24 nucleotides (nt ) of coding sequence and 119 nt of 3' UTR. This translates to a differ ence of seven amino acids at the C-termini of the polypeptide products . Utilization, in RT-PCR analysis, of form-specific primers provided a simple assay for the tissue specificity of expression of the two form s. rnRacGAP(1) is the predominant species in the testes and is express ed at a low level in the ovary and somatic tissues. rnRacGAP(2) is onl y very weakly expressed and is detectable solely in the testes.