CONSERVATION OF STRUCTURE AND EXPRESSION OF THE TRITHORAX GENE BETWEEN DROSOPHILA-VIRILIS AND DROSOPHILA-MELANOGASTER

The Drosophila melanogaster trithorax gene encodes several large RNAs which are expressed in complex patterns in the embryo. The D. virilis trithorax gene was isolated and sequenced. It produces a similar to D. melanogaster set of transcripts, and it encodes a protein that shows sequence similarity in several domains which are also conserved in the human homologue, ALL-1/HRX. Previous experiments have suggested that a distinct expression domain of trithorax in the posterior region of t he embryo is required to maintain expression of the BX-C genes (Sedkov et al., 1994, Development 120, 1907-1917). At cellular blastoderm, tr ithorax RNA expression in D. virilis embryos is also confined to the p osterior portion of the presumptive mesoderm. This finding supports th e idea that the specific BX-C-related expression domain is an essentia l feature of the trithorax gene.