Functional analysis of the transcriptional control regions of the copia transposable element.

The introduction of copia-based vectors in Drosophila hydei cells results in their high-level transient expression and the subsequent establishment of stably transformed cell lines containing multiple copies of vector integrated into host genomic DNA. Using transformation frequency and transient expression analysis as assays of promoter strength, we have defined the regions of copia essential for expression. We find that the essential sequences reside within the long terminal repeat, but 3' to the site of initiation of copia RNA. Deletion of the consensus enhancer-like sequences from copia appears to have no effect on vector expression.