The retrotransposon copia regulates Drosophila gene expression both positively and negatively

The D. melanogaster transposable element copia is structurally similar to retroviral proviruses. We have asked whether copia encodes regulatory functions which have been observed in certain other proviruses. We have introduced reporter constructs based on the copia promoter and other Drosophila promoters into Drosophila cells and asked if copia has any affect on their expression. We find that, whilst copia negatively regulates expression from its own promoter, it also positively regulates expression from the larval serum protein 1 promoter. Analysis of RNA suggests that both regulatory functions occur by post-transcriptional mechanisms.