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Review
. 2014 May;15(5):412-28.
doi: 10.1631/jzus.B1400077.

Epigenetic regulation by polycomb group complexes: focus on roles of CBX proteins

Rong-gang Ma  1 , Yang Zhang, Ting-ting Sun, Bo Cheng
Affiliations
Review

Epigenetic regulation by polycomb group complexes: focus on roles of CBX proteins

Rong-gang Ma et al. J Zhejiang Univ Sci B. 2014 May.

Abstract

Polycomb group (PcG) complexes are epigenetic regulatory complexes that conduct transcriptional repression of target genes via modifying the chromatin. The two best characterized forms of PcG complexes, polycomb repressive complexes 1 and 2 (PRC1 and PRC2), are required for maintaining the stemness of embryonic stem cells and many types of adult stem cells. The spectra of target genes for PRCs are dynamically changing with cell differentiation, which is essential for proper decisions on cell fate during developmental processes. Chromobox (CBX) family proteins are canonical components in PRC1, responsible for targeting PRC1 to the chromatin. Recent studies highlight the function specifications among CBX family members in undifferentiated and differentiated stem cells, which reveal the interplay between compositional diversity and functional specificity of PRC1. In this review, we summarize the current knowledge about targeting and functional mechanisms of PRCs, emphasizing the recent breakthroughs related to CBX proteins under a number of physiological and pathological conditions.

Keywords: Cancer; Chromobox (CBX) protein; Epigenetic regulation; Polycomb; Polycomb repressive complex 1 (PRC1).

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Conflict of interest statement

Compliance with ethics guidelines: Rong-gang MA, Yang ZHANG, Ting-ting SUN, and Bo CHENG declare that they have no conflict of interest.

This article does not contain any studies with human or animal subjects performed by any of the authors.

Figures

Fig. 1
Fig. 1
Compositional diversity and functions of PRC1 (a) Main compositions of PRC1 in fruit flies; (b) Corresponding homologs of fly PRC1 subunits in humans; (c) Main functions known about PRC1. * The assembly of RYBP/YAF2 and CBX proteins in PRC1 may be mutually exclusive
Fig. 2
Fig. 2
Domain organization and conservation among CBX proteins % of identity: ratio of the number of identical amino acid (aa) to the number of total aa; % of high conservation: ratio of the number of highly conserved aa to the number of total aa. This figure is modified from Senthilkumar and Mishra (2009)
Fig. 3
Fig. 3
Recruitment of PRC1 to chromatin through CBX proteins Recruitment through binding to histone marks H3K27me3 (a) and/or binding to ncRNA (b). Note that only RNA binding components in each complex are shown in (b)
Fig. 4
Fig. 4
Interplay among CBX proteins (a) Auto-regulation among CBX proteins in proliferating vs. differentiated mouse ESCs (mESCs); (b) Co-function among CBX proteins in human fibroblasts
See this image and copyright information in PMC

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