MOLECULAR ANALYSIS OF A COPY OF THE NOVEL MOBILE ELEMENT BURDOCK AND THE REGION OF ITS INSERTION INTO THE CUT LOCUS OF DROSOPHILA-MELANOGASTER

Molecular analysis of a copy of the novel mobile element burdock and i ts insertion region into the cut locus of Drosophila was performed. Th e burdock was shown to be a retrotransposon containing a single open r eading frame (ORF). It does not contain domens coding for protease, RN Ase H, reverse transcriptase, and integrase, which are required for tr ansposition. However, multiple insertions of this copy of the mobile e lement into a definite region of the cut locus (hot site) were observe d earlier. The polypeptide encoded by the burdock ORF contains two suc cessive regions homologous to the proteins encoded by the ORF1 and ORF 2 of the gypsy retrotransposon in N and C regions, respectively. The b urdock insertion into this region of the cut locus interrupts its ORF, since the mobile element is transcribed in the opposite direction com pared with the transcription in the locus. This is presumed to account for the arising of a lethal mutation. The hot site of this element in tegration into the locus corresponds to the recognition site of Drosop hila topoisomerase II.