PRC1-mediated gene silencing in pluripotent ES cells: function and evolution

Pluripotency is a remarkable property, which is only transiently present during development. It is functionally defined by the capacity of a cell to differentiate into all cell lineages of an organism (cell types of the three embryonic germ layers, i.e., ecto-, endo-, and mesoderm, and the germ cell lineage) and to generate pluripotent daughter cells. It seems obvious that these special features of pluripotent cells must be reflected in molecular mechanisms regulating gene expression and chromatin structure. However, defining what are the mechanisms that control pluripotency and how are the unique features of pluripotent cells established, regulated, and maintained on the molecular level is a matter of intense research. Polycomb repressive complexes (PRCs) are key epigenetic regulators of development and cell specification. Here we summarize and discuss recent data on the role of PRC1 for the establishment and maintenance of embryonic stem (ES) cell pluripotency with special emphasis on the evolution of mammalian orthologs of PRC1 components