Control of the gene activity by polycomb and trithorax group proteins in Drosophila

Combinatorial expression of the genes in multicellular organisms leads to the development of different cell types. The important epigenetic regulators of higher eukaryotes are the Polycomb group (PcG) and Trithorax group (TrxG) proteins. These factors control the transcription of a large number of genes involved in various cellular processes. Dysregulation of PcG and TrxG systems leads to developmental abnormalities and cancer. This review focuses on the main characteristics and properties of the Drosophila PRE elements. Furthermore, we summarize the information on the protein components of the PcG and TrxG groups and their functional activities and discuss the main aspects of competition between the proteins of these classes as well as their possible mechanisms of action.