Expression of dispersed 36 bp sequences in Drosophila virilis.

A major fraction of mobile dispersed elements described in Drosophila virilis (pDv elements) consists of tandem 36 bp repeats. These repeat units were cloned into pUC19 and used as a hybridization probe. DNA blotting showed that these 36 bp repeats in the D. virilis genome are included in rather large (5-6 kb) structural and probably functional domains. The 36 bp repeat units in the D. virilis and D. lummei genomes exist in three different orientations relative to one another, i.e. tail-to-tail, tail-to-head and head-to-head. These repeats are actively transcribed and, as shown by in situ hybridization studies and RNA blotting, most of their transcripts are found in nuclei. Cloning of tandem repeats into bacterial expression vectors (pEX) with subsequent immunoblotting revealed translation of these sequences predominantly in one of the three possible reading frames.