From reading, I know that epigenome has to do with gene expression, which itself is when a cell reads a gene to create a protein
Epigenetics is interesting because even though two individuals may have the same DNA(twins) but due to environmental factors, etc , their epigenome may be different.
Can someone give an explanation for how DNA methylation fits into the picture? Is methylation a technique for influencing gene expression?
In: Biology
You have it right. All nucleated cells have the same DNA sequence (assuming no retro virus and the like), but what makes cells different in functionality is which of the thousands of genes they actually express. This is dictated by which transcription factors are present which themselves need to be expressed, and the picture gets more complex. But another way of regulation is the epigenome, this is basically like you described, a way to affect the expression of a gene either by directly modifying the DNA sequence covalently or by modifying the histoens covalently. Such covalent modifications include methylation, hydroxymethylation, acetylation, phosphorylation, ubiquitination and sumoylation. These are just chemical groups or proteins added covalently to the DNA bases or the amino acids making up histones. Not all of these apply to both DNA and histones, some to both some to one or the other. And of course there are sooooo many other things in epigenetic regarding many types of RNA and such, but let’s not get too complex. Btw, histones are proteins that the DNA wraps around in many layers of organization to condense it (since it’s extremely long), and when you transcribe a gene you usually loosen this binding a bit to make it accessible, so if you modify those histones you may either reduce or enhance the tightness of the wrapping, thereby affecting gene expression. For methylation, since you’re interested in it, when it happens on DNA it is thought to recruit some proteins that repress gene expression or it directly inhibits the binding of transcription factors. When it’s on histones, it functions to wrap the tail of the histones tighter around the DNA to restrict access of transcription factors that can facilitate the expression of the gene. And methylation is not permanent, it can be written and erased, but it does play a role in genomic imprinting where your parent can transmit their DNA methylation to their offspring, that’s how x chromsome silencing works (women have two and one is silenced).
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