Article

Wallace, J. A. & Orr-Weaver, T. L. Replication of heterochromatin: insights into mechanisms of epigenetic inheritance. Chromosoma 114, 389-402

Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Chromosoma (Impact Factor: 4.6). 01/2006; 114(6):389-402. DOI: 10.1007/s00412-005-0024-6
Source: PubMed

ABSTRACT

Heterochromatin is composed of tightly condensed chromatin in which the histones are deacetylated and methylated, and specific nonhistone proteins are bound. Additionally, in vertebrates and plants, the DNA within heterochromatin is methylated. As the heterochromatic state is stably inherited, replication of heterochromatin requires not only duplication of the DNA but also a reinstallment of the appropriate protein and DNA modifications. Thus replication of heterochromatin provides a framework for understanding mechanisms of epigenetic inheritance. In recent studies, roles have been identified for replication factors in reinstating heterochromatin, particularly functions for origin recognition complex, proliferating cell nuclear antigen, and chromatin-assembly factor 1 in recruiting the heterochromatin binding protein HP1, a histone methyltransferase, a DNA methyltransferase, and a chromatin remodeling complex. Potential mechanistic links between these factors are discussed. In some cells, replication of the heterochromatin is blocked, and in Drosophila this inhibition is mediated by a chromatin binding protein SuUR.

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    • "Hence, they do not necessarily alter the frequency of switching. Mutations in other regulators produce higher levels of the expression of otherwise silenced reporters [89,90], but it is hard to tell if modest loss of repression or frequent epigenetic conversions have yielded these results. "
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    • "Such phenomena should not be linked to the switching mechanism. On the other hand, many studies have shown increased levels of expression of otherwise silenced reporters [reviewed in (3,12)]. These observations have often been attributed to ‘poor maintenance’ of gene silencing, meaning an elevated rate of S→A switches, or to incomplete repression of the gene in the PEV locus. "
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    Full-text · Article · Jul 2013 · Nucleic Acids Research
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    • "In turn, H3K9me3 is known to recruit HP1. Thus, both DNA methylation and histone methylation can immediately be reinstated after replication (for review, seeWallace and Orr-Weaver 2005;Groth et al. 2007). "
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    ABSTRACT: The progression of pluripotent stem cells to differentiated cell lineages requires major shifts in cell differentiation programs. In both mammals and higher plants, this process appears to be controlled by a dedicated set of transcription factors, many of which are kingdom specific. These divergent transcription factors appear to operate, however, together with a shared suite of factors that affect the chromatin state. It is of major importance to investigate whether such shared global control mechanisms indicate a common mechanistic basis for preservation of the stem cell state, initiation of differentiation programs, and coordination of cell state transitions.
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