ABERRANT SPLICING AND TRANSCRIPTION TERMINATION CAUSED BY P-ELEMENT INSERTION INTO THE INTRON OF A DROSOPHILA GENE

Insertional mutagenesis screens using the P[lacZ, rosy(+)] (PZ) transp osable element have provided thousands of mutant lines for analyzing g enes of varied function in the fruitfly, Drosophila melanogaster. As h as been observed with other P elements, many of the PZ-induced mutatio ns result from insertion of the P element into the promoter or 5' untr anslated regions of the affected gene. We document here a novel mechan ism for mutagenesis by this element We show that sequences present wit hin the element direct aberrant splicing and termination events that p roduce a mRNA composed of 5' sequences from the mutated gene (in this case, pipsqueak) and 3' sequences from within the P[lacZ, rosy(+)] ele ment. These truncated RNAs could yield proteins with dominant mutant e ffects.