Extrachromosomal circular copies of the eukaryotic transposable element copia in cultured Drosophila cells

Circular copies of the transposable element copia have been isolated from cultured Drosophila cells. These molecules, which are present at approximately 1 copy per 10–50 cells, comprise a heterogeneous family of related species. Most are composed of a complete copy of the internal section of copia combined with either one or two copies of the flanking direct repeat sequences. Such structures are strikingly analogous to the circular proviral forms of retroviruses.