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.