Epigenetic Regulation of Gene Expression

Abstract

The phenomenon of genes being regulated by factors and marks that do not change the underlying DNA code demonstrates the complexity inherited in genomic regulation. The exact definition of epigenetics has developed from its theoretical proposal to focus on the physical mechanism which transmits epigenetic information. This in turn has led to some controversies about how widely the definition should be applied. Repressive epigenetic marks, DNA methylation, Polycomb complex regulation by H3K27Me3 and heterochromatin protein 1 recruitment to H3K9Me3 will be the mechanisms we mainly focus on due to their robust heritability across the cell cycle. Epigenetic marks often work through changing gene expression, but it is important to note that this is not the only way they can work.

Key Concepts

  • Epigenetic mechanisms allow cells to acquire specific phenotypes without involving changes to the DNA sequence.
  • Epigenetic mark must not alter the underlying DNA sequence and should lead to changes in gene expression without the need to read the underlying sequence.
  • The main epigenetic mechanisms are DNA methylation, histone modifications and expression of noncoding RNAs.
  • Disruption to epigenetic mechanism or mistargeting of a mark can result in phenotypic change and ultimately diease.
  • The term epigenetics has developed to describe multiple mechanisms, sometimes inaccurately, which are heritable across cell division.

Keywords: epigenetics; gene regulation; DNA methylation; histones modifications; nucleosome; heterochromatin; euchromatin; chromatin; Polycomb complexes

Figure 1. The arrangement of chromatin fibres in the two major chromatin structures and how these marks and factors either allow or block transcription.
Figure 2. (a) Summary of 5mC's repressive action through recruitment of different MBD proteins when placed around a promoter. (b) Nucleosome positioning around an active promotor including lack of 5mC. (c) 5hmCs potential mechanisms of resetting 5mC marks and altering proteins that can bind at the site.
Figure 3. Mechanism for the propagation of 5mC through DNMT1 activity after DNA replication.
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Further Reading

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How to Cite close
Murison, Keir, and Michod, David(May 2020) Epigenetic Regulation of Gene Expression. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0028374]