The transcriptional control regions of the copia retrotransposon.

We have analysed the sequence elements that control expression of the copia retrotransposon. Expression of copia fusion constructs containing DNA sequence deletions and rearrangements was assayed by transient expression analysis. Progressive deletion and linker substitution identifies two regions on either side of the major transcriptional start sites in the copia long terminal repeat These regions are both required for high level expression in a cultured Drosophila melanogaster cell line but only the upstream region is required for copia expression in a Drosophila hydei cell line. A third control region lies downstream of the long terminal repeat in a region previously believed to contain no cis-acting regulatory sequences. We show by displacement and inversion of this region that it contains a transcriptional enhancer.