Complexity and Diversity of Polycomb Group Proteins: How Do They Work?

Polycomb group (PcG) proteins are a group of modified transcriptional regulation of target genes through the biochemical and functional chromatin repressors, it can be divided into two major core protein complexes which are polycomb repressive complex 1 (PRC1) and polycomb repressive complex 2 (PRC2) through the biochemical and functional. Some studies have found that PcG proteins were not only correct the development mode of individual organisms, but also have correlation with cell proliferation, differentiation and tumorigenesis. In the other side, recent researches showed that some core complexes of PRC1 and PRC2, which are enhancer of zeste homolog 2 (EZH2), Chromobox (CBX) family proteins, human polyhomeotic homolog (HPH), and the E3-ligase protein (RING), are far more varied than previously thought. There is no clear insight into how many functional PRC1/2 complexes exist and what the biological relevance is for such diversification. Thus, we review the growing functions of the non-canonical PRC1 complex and the major complex of PRC2 which is EZH2 and discuss their potential roles in cancer progression.