Sequences homologous to the hobo transposable element in E strains of Drosophila melanogaster

Hobo is one of the three Drosophila melanogaster transposable elements, tog ether with the P and I elements, that seem to have recently invaded the gen ome of this species. Surveys of the presence of hobo in strains from differ ent geographical and temporal origins have shown that recently collected st rains contain complete and deleted elements with high sequence similarity ( H strains), but old strains lack hobo elements (E strains). Besides the can onical hobo sequences, both H and E strains show other poorly known hobo-re lated sequences. In the present work, we analyze the presence, cytogenetic location, and structure of some of these sequences in E strains of D. melan ogaster. By in situ hybridization, we found that euchromatic. hobo-related sequences were in fixed positions in all six E strains analyzed: 38C in the 2L arm; 42B and 55A in the 2R arm; 79E and 80B in the 3L arm; and 82C, 84C , and 84D in the 3R arm. Sequence comparison shows that some of the hobo-re lated sequences from Oregon-R and iso-1 strains are similar to the canonica l hobo element, but their analysis reveals that they are substantially dive rged and rearranged and cannot code for a functional transposase. Our resul ts suggest that these ubiquitous hobo-homologous sequences are immobile and are distantly related to the modem hobo elements from D. melanogaster.