Effects of transposable element insertions on RNA encoded by the white gene of Drosophila.

We have examined the manner in which transposable element insertions affect the expression of the white gene of Drosophila by analyzing polyadenylated RNA of flies with each of nine insertions in or near the gene. In five mutants having insertions in the transcribed sequences of white, transcripts initiating at the white promoter are truncated within the insertions. Two insertions in the 3 kb intron of white alter neither the amount nor the structure of the mature white RNA. An insertion near the 5' end of the gene blocks the accumulation of any white transcripts. Another insertion, located 1.2 kb upstream from the transcribed region of the gene, causes a mutant phenotype yet surprisingly has no obvious effect on the structure or abundance of the major white RNA. We also show that a mutation at each of two other loci that modulate the phenotype of the white-apricot insertion mutant are correlated with small but significant changes in the pattern of white transcripts.