Using physics and a tiny magnet, researchers have discovered a new structure of telomeric DNA. Telomeres are sometimes seen as the key to living longer. They protect the genes from damage, but they get a little shorter each time a cell divides. If they become too short, the cell dies. The new discovery will help us understand aging and disease.
Physics is not the first scientific discipline that comes to mind when DNA is mentioned. But John van Noort of the Leiden Institute of Physics (LION) is one of the scientists who discovered the new structure of DNA. A biophysicist, he uses methods from physics for biological experiments. This also caught the attention of biologists at Singapore’s Nanyan Technological University. They asked him to help study the DNA structure of telomeres. They published the results in The nature.
String of beads
In every cell of our body there are chromosomes that carry genes that determine our characteristics (how we look, for example). At the ends of these chromosomes are telomeres, which protect the chromosomes from damage. They are a bit like aglets, the plastic tips at the end of the shoelace.
The DNA between telomeres is two meters long, so it must be folded to fit in a cell. This is done by wrapping DNA is wrapped around bundles of proteins; together, the DNA and proteins are called a nucleosome. They are arranged in something similar to a string of beads, with a nucleosome, a piece of free (or unbound) DNA, a nucleosome, and so on.
This string of beads is then folded further. How it does this depends on the length of the DNA between the nucleosomes, the beads on the string. Two structures that appear after folding were already known. In one of them, two adjacent beads stick together and free DNA dangles between them (Fig. 2A). If the piece of DNA between the beads is shorter, adjacent beads fail to stick together. Then two stacks are formed side by side (fig. 2B).
In their study, Van Noort and colleagues discovered another structure of telomeres. Here the nucleosomes are much closer, so there is no more free DNA between the beads. This eventually creates a large DNA helix (Fig. 2C).
The new structure was discovered with a combination of electron microscopy and molecular force spectroscopy. The latest technique comes from Van Noort’s lab. Here one end of the DNA is attached to a glass slide and a magnetic ball is glued to the other. A set of powerful magnets above this ball then pulls the string of pearls. By measuring the amount of force required to separate the beads one by one, you learn more about how the string is folded. The Singaporean researchers then used an electron microscope to get a better picture of the structure.
Structure, Van Noort says, is “the Holy Grail of molecular biology.” If we know the structure of the molecules, this will give us more information about how genes are turned on and off, and how enzymes in cells deal with telomeres: how they repair and copy DNA, for example. Discovering the new telomeric structure will improve our understanding of the building blocks in the body. And that, in turn, will ultimately help us study aging and diseases like cancer and develop drugs to combat them.
Bending DNA costs less energy than thought
Aghil Soman et al., Columnar structure of human telomeric chromatin, The nature (2022). DOI: 10.1038/s41586-022-05236-5
Provided by Leiden University
Citation: Can we live longer? Physicist Makes Discovery About Telomeres (2022, September 15) Retrieved September 21, 2022, from https://phys.org/news/2022-09-longer-physicist-discovery-telomeres.html
This document is subject to copyright. Except for any fair dealing for the purpose of private study or research, no part may be reproduced without written permission. The content is provided for informational purposes only.