TERMINAL REPEATS OF THE DROSOPHILA TRANSPOSABLE ELEMENT COPIA - NUCLEOTIDE-SEQUENCE AND GENOMIC ORGANIZATION

The nucleotide sequence of the terminal regions of 2 members of the copia sequence family of D. melanogaster was determined. The first 276 bp [base pairs] at 1 end of a copia element are repeated in direct orientation at its other end. The direct repeats on a single copia element are identical to each other, but they differ by 2 nucleotide substitutions between the 2 elements which were examined; this suggests that during transposition only 1 direct repeat of the parent element is used as a template for both direct repeats of the transposed element. Each direct repeat itself contains a 17 bp imperfectly matched inverted terminal repetition. The ends of copia show significant sequence homology both to the yeast Ty1 element and to the integrated provirus of avian spleen necrosis virus, 2 other eukaryotic elements known to insert at many different chromosomal locations. Analysis of the genomic organization of the direct repeat sequence demonstrates that it seldom, if ever, occurs unlinked to an entire copia element.