Research on the Role of GTGT Motives in Polycomb/Trithorax Response Elements and Their Non-Coding RNAs in Flies and Mice

cG and TrxG proteins constitute an epigenetic regulatory machinery that regulates key developmental genes by binding to specific cis regulatory elements called PREs/TREs (Polycomb or Trithorax response elements) in Drosophila. Functional mammalian PRE homologs have been suggested to the hypomethylated CpG islands. How PcG proteins are specifically recruited to PREs/CpG islands is a field of extensive research, but many enigmatic questions remain unanswered so far. At the sequence level PREs are very heterogeneous in Drosophila, and the sequence requirements in mammals seem to be quite different. In addition ncRNAs have been implicated in the recruitment of PcG proteins and the switching of PREs into TREs, however their precise role remains hotly debated.