Can we live longer? Physicist makes discovery about telomeres

Using physics and a tiny magnet, researchers have discovered a new structure of telomeric DNA. Telomeres are sometimes considered the key to longer life. They protect genes from damage, but become slightly shorter with each cell division. 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 found the new DNA structure. The biophysicist uses methods of physics for biological experiments. This also caught the attention of biologists at Nanyan Technological University in Singapore. They asked him to help study the DNA structure of telomeres. They published the results in Nature.

string of beads

Every cell in our body contains chromosomes that carry genes that determine our characteristics (like how we look). At the ends of these chromosomes are telomeres that protect the chromosomes from damage. They’re a bit like aglets, the plastic tips at the end of a shoelace.

The DNA between telomeres is two meters long, so it has to be folded to fit in a cell. This is accomplished by wrapping the DNA around packets of proteins; Together, DNA and proteins are called a nucleosome. These are arranged like a string of pearls, with a nucleosome, a piece of free (or unbound) DNA, a nucleosome, and so on.

This string of pearls then folds up even more. How this is done depends on the length of 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 hangs between them (Fig. 2A). If the piece of DNA between the beads is shorter, the adjacent beads will not be able to stick together. Two stacks are then formed side by side (Fig. 2B).

In their study, Van Noort and colleagues found a different telomere structure. Here the nucleosomes are much closer together, so there is no longer any free DNA between the spheres. This ultimately creates a large DNA helix or spiral (Fig. 2C).

The new structure was discovered using a combination of electron microscopy and molecular force spectroscopy. The latter technique comes from Van Noort’s laboratory. Here, one end of the DNA is attached to a glass slide and the other end is attached to a small magnetic ball. A set of strong magnets above this sphere then pulls the string of beads apart. By measuring the force required to pull the beads apart one at a time, you’ll learn more about how the string is folded. The researchers in Singapore then used an electron microscope to get a better picture of the structure.

Structure, says Van Noort, is “the holy grail of molecular biology”. If we know the structure of the molecules, we can better understand how genes are switched on and off and how enzymes in cells deal with telomeres: how they repair and copy DNA, for example. The discovery of the new telomere 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.