Epigenetics: Science of Changes without Change in DNA Sequences

Abstract

The mechanisms for epigenetic modifications include modification of histone proteins or modifications of the DNA itself (not affecting the DNA sequence). These include acetylation, methylation, phosphorylation, SUMOylation, ubiquitylation, etc. For example, DNA methylation (cytosine methylation) or histone acetylation (lysine acetylation). Recent studies have indicated that the activity of non-coding RNAs, such as microRNAs, long non-coding RNAs, and small interfering RNAs also affects epigenetic mechanisms. In a genome, the collection of all the modifications that regulate gene expression is called its epigenome. Improper occurrence of the epigenetic mechanisms can lead to deleterious health and behavioral effects. For instance, the most studied epigenetic modification is DNA hypermethylation, which leads to the silencing of antitumorigenic genes, and this has been shown to cause cancer. Various techniques are employed for DNA methylation profiling such as pyrosequencing, bisulfite-PCR, ChIP seq (Chromatin Immunoprecipitation), bisulfite seq, and specialized RNA seq. This chapter will introduce epigenetics, describe the different epigenetic mechanisms, and discuss in brief how to study these mechanisms and their effects on the plant as well as human health.