DROSOPHILA GENES POSTERIOR SEX COMBS AND SUPPRESSOR 2 OF ZESTE ENCODE PROTEINS WITH HOMOLOGY TO THE MURINE BMI-1 ONCOGENE

THE Polycomb group (Pc-G) genes are needed to maintain expression patterns of the homeotic selector genes of the Antennapedia (Antp-C) and bithorax (bx-C) complexes, and hence for the maintenance of segmental determination 1-3. We report the predicted protein sequence of the Pc-G gene Posterior Sex Combs (Psc), and of the neighbouring and related gene Suppressor two of zeste (Su(z)2). Both genes encode large proteins that contain a 200 amino-acid domain identical over 37.4% that is also conserved in the murine oncogene bmi-1 (refs 4, 5). At the amino terminus of this domain is a cysteine-rich sequence that has been proposed as a novel type of zinc finger 6.