Sequence, molecular organization and products of the Drosophila virilis homologs of the D. melanogaster nested genes lethal(2) tumorous imaginal discs [1(2)tid] and lethal(2) neighbour of tid [1(2)not].

In this study, we describe the isolation of the Drosophila virilis (Dvir) 6201-bp genomic fragment homologous to a 7047-bp genomic region of D. melanogaster (Dmel) that harbors the nested genes lethal(2) tumorous imaginal discs (l(2)tid), lethal(2) neighbour of tid (l(2)not) and lethal(2) relative of tid (l(2)rot). The isolated fragment, which maps at the cytogenetic position 50A5 on chromosome 5, carries the Dvir homologs of the Dmel genes l(2)tid and l(2)not. In both cases, the interspecific comparison of the determined sequences reveals a high homology regarding the protein coding regions and a high degree of evolutionary divergence concerning the intronic parts of the genes. In the two distantly related species, the particular gene within gene arrangement of the two genes is conserved, namely, Dvir tid is located in the intron of Dvir not, on the non-coding DNA strand. Interestingly, the Dvir homolog of the Dmel l(2)rot gene residing in the l(2)not intron on its coding strand, opposite l(2)tid, is not present in the 6201-bp genomic fragment. The protein predicted from the Dvir tid sequence, Dvir Tid58, exhibits 76.5% identity with the putative Tid56 protein of Dmel. The putative Dvir Not58 protein shows 71% identity with its Dmel homolog Not56. The developmental transcript and protein patterns, as well as the characteristics of the protein products encoded by the genes Dvir tid and Dvir not are similar to those identified for their Dmel homologs.