What is DNA Methylation and What is its role in gene expression?
DNA methylation can best be described as a biochemical process that plays a crucial part in the development of all organisms. While its exact role in gene expression is not yet determined, evidence suggests that proper methylation is extremely crucial in cell differentiation, embryonic development and other vital life processes.
DNA methylation basically involves the addition of a methyl group to a highly specific region in the DNA sequence, particularly in the 5 position of the cytosine pyrimidine ring or the number 6 nitrogen of the adenine purine ring. It usually occurs in the CpG site, an area in the DNA sequence where a cytosine nucleotide is located next to a guanine nucleotide linked by a phosphate. Once the CpG sites are methylated by either one of the DNA methyltransferases DNMT1, DNMT3a and DNMT3b, the appearance and structure of the DNA will be altered and the gene's interactions with the cell's nucleus will likewise undergo some modifications.
The Many Functions of DNA Methylation in Gene Expression
Researchers have long since established that DNA methylation is involved in vital biological processes such as embryonic development, genomic imprinting, gene silencing and X-chromosome inactivation. It can alter the gene expression pattern in cells to decrease gene expression or to let the cells "remember where they have been" without the need for any continuing signals.
While DNA methylation suppresses viral genes and other harmful elements that have been incorporated in the genome of the host from expressing themselves, aberrations in methylation patterns can cause hypermethylation or hypomethylation, both of which are implicated in the development of cancer. In addition, such aberrations are likewise implicated in the development of Rett syndrome (a brain disorder that mostly affect women) and Von Hippel-Lindau disease or VHL (a rare genetic condition that increases one's susceptibility to benign and malignant tumors).
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