Regulation of the genes of the bithorax complex in Drosophila

Abstract

The bithorax complex (BX-C) is a set of master con-trol genes that regulates other genes outside the com-plex to program much of the development of the thorax and abdomen of the fly. The emphasis in this paper will be on how the genes of the complex are themselves regulated, rather than on how they regulate other genes. The BX-C is regulated in cis and in trans. Only a brief review of its regulation by trans-acting loci will be given, since our primary concern in this paper is to identify the rules that govern regulation in cis and to outline a model for cis-regulation based on these rules. Regulation of the BX-C in trans appears to be chiefly negative in the sense that loss-of-function alleles at several loci outside the complex are known to result in derepression of BX-C genes in regions of the body where the latter are normally repressed. Examples ar