Polycomb group complexes – many combinations, many functions

Epigenomics, 2015

Polycomb group (PcG) proteins play an important role in the regulation of gene expression, especially genes encoding lineage-specific factors. Perturbations in PcG protein expression may trigger an unexpected developmental pathway, resulting in birth defects and developmental disabilities. Two Polycomb repressive complexes, PRC1 and PRC2, have been identified and are related with diverse cellular processes through histone modifications. Many developmental genes are trimethylated at histone H3 lysine 27 (H3K27me3) mediated by PRC2, which provides a binding site for PRC1. These processes contribute to chromatin compaction and transcriptional repression. In this review, we discuss about the complex formation of PcG proteins, the mechanism through which they are recruited to target sites and their functional roles in cell differentiation.

Cell Cycle, 2006

Developmental Cell, 2010

The Polycomb group (PcG) system represses the transcription of important developmental regulators and perpetuates this repression across multiple cell divisions. Inputs from outside the cell can influence PcG function by recruiting additional chromatin factors to PcG-regulated loci or by downregulating the PcG genes themselves. These types of PcG system modulation allow context-dependent induction of genes during development, in cancer, and in response to changes in the environment. In this review, we outline instances where molecular players in this process have been recently identified, comparing and contrasting different ways in which derepression is achieved, and projecting directions for future research.

The PcG (Polycomb group of proteins) refers to a factors subset that has the ability to associate physically as well as facilitating the maintenance of the cells positional identity from conception to the adult stage (Almutairi & Sadder, 2014). Thus, there has been consideration of the PcG for a long time in the paradigmatic models for the maintenance of the epigenetic of the programs of gene transcription. However, despite the efforts in the research of revealing the mechanical actions of the molecules of the PcG proteins, there still exist various questions. For instance, there needs to be an understanding of the method in which transcription is regulated by the PcG. Therefore, the paper attempts to offer a discourse on the diversity that exists in the mammalian cells of the complexes of the PcG. It also offers a discussion of the recent advances in the PcG mediated regulation of the gene.

Epigenetics and human health, 2014

The Polycomb group (PcG) products are a set of evolutionary conserved proteins that form chromatin regulator complexes that control expression of developmentally relevant genes. PcG activity is essential not only to maintain the developmental potential of pluripotent cells from which specialized cell types arise, but also to ensure the directionality of the differentiation process. In the adult, these PcG functions are essential for normal cell homeostasis and their deregulation is often associated with cell transformation events. PcG-dependent transcriptional control involves posttranslational modifications of histones, decreased DNA accessibility, and other mechanisms. While the stability of Polycomb-determined chromatin landscapes is rather stable in differentiated cells, in pluripotent cells it is characteristically dynamic in order to accommodate the execution of developmental genetic programs. Best known as repressors of gene expression, recent evidence points at roles during gene activation. Besides gene expression control, PcG products also participate in other essential functions such as DNA damage response, indicating that these proteins are involved in a wide spectrum of cellular and organismal functions in need of detailed characterization.

Molecular Cell, 2014

FEBS Journal, 2014

Polycomb group proteins (PcGs) are a large protein family that includes diverse biochemical features assembled together in two large multiprotein complexes. These complexes maintain gene transcriptional repression in a cell type specific manner by modifying the surrounding chromatin to control development, differentiation and cell proliferation. PcGs are also involved in several diseases. PcGs are often directly or indirectly implicated in cancer development for which they have been proposed as potential targets for cancer therapeutic strategies. However, in the last few years a series of discoveries about the basic properties of PcGs and the identification of specific genetic alterations affecting specific Polycomb proteins in different tumours have converged to challenge old dogmas about PcG biological and molecular functions. In this review, we analyse these new data in the context of the old knowledge, highlighting the controversies and providing new models of interpretation and ideas that will perhaps bring some order among apparently contradicting observations.

Science Advances, 2017

The PRC1 complex keeps genes silent during development, and these studies show that it also controls genes that are active.

Nature, 2006

Development, 2009