For decades, researchers in the genetics field have theorized that the protein spools around which DNA is wound, histones, remain constant in the brain, never changing after development in the womb. Now, researchers from the Icahn School of Medicine at Mount Sinai in New York have discovered that histones are steadily replaced in brain cells throughout life - a process which helps to switch genes on and off. This histone replacement, known as turnover, enables our genetic machinery to adapt to our environment by prompting gene expression, i.e., the conversion of genes into the proteins that comprise cellular structures and carry signals in the brain. This new concept, described in a study led by researchers in the Department of Pharmacology and Systems Therapeutics at the Icahn School of Medicine at Mount Sinai, and at the Laboratory of Chromatin Biology and Epigenetics, The Rockefeller University, was published in the July 1, 2015 issue of the journal Neuron. The article is titled “Critical Role of Histone Turnover in Neuronal Transcription and Plasticity.” The study's findings argue against the long-held belief that histones, part of the chromatin structure that packages and protects genetic material in chromosomes, are highly stable proteins in non-dividing cells like nerve cells. The study authors argue that aging histones are instead constantly replaced with new histones, rather than being created once and remaining attached to DNA throughout a person's life. The newfound mechanism is epigenetic, meaning it fine-tunes gene expression without changing the DNA code we inherit from our parents.
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