Cell identity is reflected by changes in chromatin status. In HSCs, PRC1 and PRC2 complexes help to repress genes involved in differentiation to allow the maintenance of stem cell properties. Differentiation induces displacement of PcG members and relocation to promoters of stemness genes. In cancer, the aberrant PcG activity induces a repression of differentiation promoting genes as well as tumor suppressor genes. In this case, the recruitment of DNMTs induces permanent repression of the genes.