THE ORGANIZATION OF THE GENE FOR DROSOPHILA LAMIN-C - LIMITED HOMOLOGY WITH VERTEBRATE LAMIN GENES AND LACK OF HOMOLOGY VERSUS THE DROSOPHILA LAMIN DMO GENE

Drosophila melanogaster has, in addition to the well characterized lam in Dmo, a second nuclear lamin called lamin C, which was recently defi ned by cDNA cloning. Here we characterize the gene encoding Drosophila lamin C. It is composed of 4 exons and 3 introns, which all interrupt the coding sequence. No intron position of the Drosophila lamin C gen e has a counterpart in the Drosophila lamin Dmo gene, which has a stru cture unrelated to the highly conserved structures of vertebrate lamin genes. Surprisingly, however, two of the three intron positions of th e Drosophila lamin C gene are also found in all currently known, verte brate lamin genes, which have an additional 8 to 9 introns. Thus, lami n genes from vertebrates and invertebrates can be more closely related in organization than earlier thought on the basis of only two inverte brate genes. The striking difference in structure of the two Drosophil a Iamin genes indicates that their ancestral genes separated earlier i n metazoan evolution and that more than one lamin gene may also be exp ected in other invertebrates.