ROLE OF MULTIPLE TRANS-ACTING REGULATORS IN MODIFYING THE EFFECT OF THE RETROTRANSPOSON COPIA ON HOST GENE-EXPRESSION IN DROSOPHILA

We have examined the combinatorial effect of five trans-acting modifie rs of white apricot, a copia retrotransposon-induced allele of the whi te eye-color gene. Quantitation of steady-state levels of copia transc ripts for various modifier combinations at different developmental sta ges using northern analysis reveals nonadditivity and epistasis. Inter estingly, extensive overexpression of copia transcripts caused by the modifier Ufo is altered up to twofold in level when Ufo is combined wi th either of the modifiers Mow or Wow. In general, double combinations do not elevate the level of copia transcripts more than twofold. The role of suppressor mutations in modifying the effect of transposable e lements on host gene expression is discussed.