A retrotransposon 412 insertion within an exon of the Drosophila melanogaster vermilion gene is spliced from the precursor RNA.

Three alleles of the Drosophila melanogaster vermilion (v) gene are suppressed by recessive mutations at the suppressor of sable [su(s)], gene. Previous work has established that these alleles have identical insertions of the 412 retrotransposon in the 5'-untranslated region of the gene. Despite the transposon insertion in an exon, v mutants accumulate trace amounts of apparently wild-type-sized transcripts in a su(s)+ background, and the level of v transcript accumulation is increased by su(s) mutations. Here, we have characterized transcripts from a suppressible v mutant in both su(s)+ and su(s)- backgrounds by S1 nuclease protection experiments and sequence analysis of polymerase chain reaction (PCR) generated cDNA clones. We find that transposon sequences are imprecisely eliminated from v mutant transcripts by splicing at donor and acceptor sites located near the ends of the 412 retrotransposon. Four different 5' donor sites are alternatively spliced to a single 3' acceptor site. The implications of this finding are discussed in relation to possible functions of the su(s)+ gene product.