How exactly is Epigenetic information encoded and stored in humans?

Question

I watched a video on Youtube: “How to Slow Aging (and even reverse it)”, which stated simply that the main driver of aging process is the loss of epigenetic information

if there’s the loss of it, how is it this information encoded and stored? If the genetic information is stored in our DNA, then is there something similar to the DNA for epigenetic information?

So far, I’ve only seen vague explanations that epigenetic mechanisms are realized mainly through nucleosomes, which unwrap the wrapped DNA, thus allowing its certain section to be used for transcription

And that the degree of DNA methylation (addition of methyl groups to the DNA) is the way to measure the epigenetic loss

However, it doesn’t explain the main question about epigenetic encoding. It also doesn’t explain: how do “Yamanaka factors” – “restore” that epigenetic information?

In: Biology

Answer 1

In DNA/RNA, information is made up from the sequence of nucleotides (ATCG). Any changes you make to these molecules that *doesn’t* alter the nucleotide sequence but *does* alter their accessibility constitutes epigenetic information. That can range from DNA methylation but also various modifications to the histones that DNA is coiled around (together forming a nucleosome).

I think you have a misconception with regard to more methylation = loss of epigenetic information. That in itself *is* epigenetic information. But methylation of DNA (it’s more complicated in histones) is associated with transcriptional repression, so if anything, what is being lost is the active expression of particular genes. That’s generally a normal part of cells differentiating, as they shut down the parts of the genome they won’t be using anymore in their new identity. I’m guessing that’s also where the Yamanaka factors enter your story; these are a set of transcription factors that, when forcibly expressed, can return a cell to a less differentiated, more stem-like state.

As for how they (and other transcription factors) work: they’ll at least have one domain that binds particular motifs (response elements) across the genome, and another domain that either performs a particular modification or recruits other factors to do so. The polycomb repressive complexes are textbook examples of the latter, though as the name implies these perform the transcription-repressing histone H3 lysine 27 trimethylation.