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Reflections on the Significance of DNA Methylation in Living Organisms: from Bacteria to Humans

Zeynep Yeğin* and Cumhur Avşar

Epigenetics refers to the study of heritable changes in gene expression which occur without a change in DNA sequence and DNA methylation constitutes one of the most important causative components of this regulation. Unlike DNA mutations, changes in DNA methylation can be influenced by the environmental factors, they are stable at the time scale of an individual and present different levels of heritability. Efficient resistance systems against phage infections in bacteria take advantage of methylation mechanisms and these defence systems became invaluable tools in biotechnological applications. An evolutionary pattern of genome methylation guides us for a better understanding of specific functions in diverse organisms. In human diseases, in contrast to mutations which typically occur at a wide range of sites, aberrant methylation of specific promoter regions is a consistent feature of cancer. Thus, the determination of these circulating methylation epigenotypes is quite advantageous in terms of reflecting the early stages of carcinogenesis and predetermining the future cancer type. In this commentary, we aim to provide an overview of the concepts and molecular mechanisms related with the methylation in living organisms. Understanding how methylation dynamically contributes to both prokaryotic and eukaryotic life forms holds much promise for perceiving the value of epigenetic processes in evolutionary and clinical practice.