The “zombie cells” that lurk in the body and contribute to age-related diseases make tiny, strange molecules not seen in normal cells. The exact function of these “hidden” molecules remains a mystery, but now scientists think they may know why zombies built them in the first place. said the scientist (Opens in a new tab).
Zombie cells, scientifically known as “senescent” cells, do not die, but stop dividing due to damage or stress. These dead cells secrete molecules that swarm the immune system and cause inflammation. Aging cells aren’t all bad — some studies suggest they are Helps repair damaged tissues —but as the body ages, these zombies begin to build up and cause inflammation that contributes to age-related diseases like cancer, Alzheimer’s, and osteoporosis.
In addition to churning out inflammatory molecules, senescent cells undergo a process called “stealth transcription,” reports The Scientist. This process describes when cells mistakenly use ultrashort snippets of DNA — just fragments of genes — to build small molecules of RNADNA’s molecular cousin. Normally, cells use RNA as blueprints for building proteins, among other things.
Normally, cells read genes starting at specific locations on the DNA molecule. Think about how a capital letter marks the beginning of a sentence and a period that indicates the end – genes have similar starting and ending points. However, in cryptic transcription, cells may start reading in the middle of a “sentence” of DNA, and this leads to the cell creating an unusually short RNA molecule.
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The exact function of these encoded RNAs is still unknown. but, Payal Sen (Opens in a new tab)The molecular biologist at the National Institute on Aging at the National Institutes of Health (NIH), said she suspects that the production of these small molecules may drain a cell’s resources, causing it to grow less and less efficiently with age. Furthermore, the cell may use the instructions within the RNA to build small proteins that somehow interfere with the normal functions of the cell.
Knowing why zombie cells undergo cryptic transcription and how this affects aging could be key to scientists’ overall understanding of the aging process, as well as their attempts to extend life and prevent age-related diseases. In a new study published March 31 in the journal nature aging (Opens in a new tab)Sen and her colleagues set out to uncover the “why” behind this phenomenon.
The team identified more than 350 “hidden sites” in senescent human cells, which means they have located the gene fragments that make up the foreign RNA. They also identified “epigenetic” changes at these sites that were not present in healthy young cells and may explain why cryptic transcription occurs.
Epigenetics literally means “over genes” and refers to molecules that attach to DNA and influence genes that can be used to make proteins. The epigenetic changes observed in the zombie cells were seen specifically in histones — the pulley-like proteins in chromosomes around which DNA coils — and the changes appear to be related to the cells’ ages. In zombie cells, these epigenetic changes exposed parts of the genome to the cells’ RNA-making machinery, whereas in young cells, the same gene fragments were “hidden” and therefore not expressed.
This finding supports the idea that zombie cells undergo coding transcription because their ability to control gene expression wears off over time, as such epigenetic changes accumulate on top of their DNA. Read more at the world (Opens in a new tab).