HOBO INDUCED REARRANGEMENTS IN THE YELLOW LOCUS INFLUENCE THE INSULATION EFFECT OF THE GYPSY SU(HW)-BINDING REGION IN DROSOPHILA-MELANOGASTER

The su(Hw) protein is responsible for the insulation mediated by the s u(Hw)-binding region present in the gypsy retrotransposon. In the y(2) mutant, su(Hw) protein partially inhibits yellow transcription by rep ressing the function of transcriptional enhancers located distally fro m the yellow promoter with respect to gypsy. y(2) mutation derivatives have been induced by the insertion of two hobo copies on the both sid es of gypsy: into the yellow intron and into the 5' regulatory region upstream of the wing and body enhancers. The hobo elements have the sa me structure and orientation, opposite to the direction of yellow tran scription. In the sequence context, where two copies of hobo are separ ated by the su(Hw)-binding region, hobo-dependent rearrangements are f requently associated with duplications of the region between the hobo elements. Duplication of the su(Hw)-binding region strongly inhibits t he insulation of the yellow promoter separated from the body and wing enhancers by gypsy. These results provide a better insight into mechan isms by which the su(Hw)-binding region affects the enhancer function.