Silencing chromatin: comparing modes and mechanisms

Abstract

Recent transcriptome analyses show that substantial proportions of eukaryotic genomes can be copied into RNAs, many of which do not encode protein sequences. However, cells have developed mechanisms to control and counteract the high transcriptional activity of RNA polymerases in order to achieve cell-specific gene activity or to prevent the expression of deleterious sequences. Here we compare how two silencing modes - the Polycomb system and heterochromatin - are targeted, established and maintained at different chromosomal locations and how DNA-binding proteins and non-coding RNAs connect these epigenetically stable and heritable structures to the sequence information of the DNA.

Gene Silencing and Polycomb Group Proteins: An Overview of their Structure, Mechanisms and Phylogenetics

“…Argonaute proteins exert their silencing role in the cytoplasm at the translational level and in the nucleus at the transcriptional level (for a review, see Guang et al, 2008). Despite recent progress in understanding and modeling the biological functions of ncRNAs in PcG-mediated silencing pathways (for a review, see Beisel and Paro, 2011), our understanding of epigenetics is still in its infancy, and further studies are required to thoroughly understand and grasp epigenetic silencing mechanisms.…”

“…Several models have been proposed to describe the dynamic behavior of Pc complex binding (Beisel and Paro, 2011;Bracken and Helin, 2009;Hansen et al, 2008;Lanzuolo et al, 2011).…”

The use of genes for performance enhancement: doping or therapy?

“…The first includes epigenetic modifications and mutations. Through epigenetics, the degree of gene transcription is altered, without causing changes in DNA sequence (5). Also of importance, mutations promote changes in the nucleotide sequence of the gene and can derail the process of transcription or generate a new product, different from the original (6).…”

Erratum: A positive role for polycomb in transcriptional regulation via H4K20me1

“…PRC1 has four core proteins: Pc, Polyhomeotic (Ph), Sex combs extra (Sce, also known as dRing) and Posterior sex combs (Psc) in Drosophila. Pc can specifically recognize H3K27me3 through its chromodomain, and recruit other components to selected chromatin sites [9,10], although H3K27me3-independent recruitment of PRC1 has also been reported in mammals [7,11]. It is generally considered that PRC1 maintains the repression of their targets by either catalyzing H2A mono-ubiquitination [12] or inducing local chromatin condensation [13][14][15][16].…”