Abstract: A method of detecting Polycomb Repressive Complex (PRC) activity in a cell providing a cell with a DNA having a protein binding site and at least one reporter gene expression site is operatively connected to the protein binding site, and with a DNA containing a recombinant gene of a binding protein, the binding protein being capable of binding to the protein binding site, wherein the binding protein is fused to a member of the PRC, the method including the step of expressing the recombinant gene, letting the fused binding protein bind to the protein binding site and detecting at least one reporter gene expression.