Can we live longer? The physicist discovers telomeres

Figure 1: Cell, Chromosome, and Telomeres. credit: vin levlange/leiden university

With the help of physics and tiny magnets, researchers have discovered a new structure for telomeric DNA. Telomeres are sometimes seen as the key to living longer. They protect the genes from damage but get a little shorter each time the cell divides. If it becomes 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, who uses methods from physics for biological experiments. This also caught the attention of biologists from Nanyan Technological University in Singapore. They asked him to help study the structure of the DNA of Telomeres. They have published the results in temper nature.

bead chain

In every cell of our body there are chromosomes that carry genes that define our characteristics (what we look like, for example). At the ends of these chromosomes are telomeres, which protect chromosomes from damage. They look a bit like lavender, and the plastic tips are at the end of a shoelace.

The DNA between telomeres is two meters long, so it must be folded to fit the cell. This is accomplished by wrapping DNA around bundles of proteins. Together, DNA and proteins are called a nucleosome. They are arranged in something similar to a string of beads, with a nucleosome, a piece of DNA (or unbound), a nucleosome, etc.

Can we live longer?  Leiden physicist discovered the protective layer of genes

Figure 2: The three different DNA structures. credit: vin levlange/leiden university

Then fold this string of beads over. How to do this depends on the length of the DNA between the nucleosomes, and the beads on the thread. The two structures that occur after folding were already known. In one, two adjacent beads stick together and free DNA dangles between them (Fig. 2a). If the piece of DNA between the beads is shorter, the adjacent beads will not be able to stick to each other. Then two sets of stacks form side by side (Fig. 2b).

In their study, Van Noort and colleagues found another telomere structure. Here the nucleosomes are much closer together, so there is no longer any free DNA between the beads. This eventually leads to the creation of a large helix or a single helix of DNA (Fig. 2C).

The new structure was discovered by a combination of electron microscopy and molecular force spectroscopy. The latest technology comes from the Van Noort lab. Here one end of the DNA is attached to a glass slide and a small magnetic ball is attached to the other end. A bunch of powerful magnets click this ball and then separate the string of pearls. By measuring how much force is needed to separate the beads one by one, you can learn more about how to fold the thread. Then researchers in Singapore used Electron microscope To get a better picture of the structure.

Synthesis is “the holy grail of molecular biology,” says van Noort. If we know the structure of molecules, this will give us more insight into how genes are turned on and off and how enzymes in cells deal with telomeres: how they repair and copy DNA, for example. The discovery of the new telomeric structure will improve our understanding of the building blocks of the body. This, in turn, will eventually help us study aging and diseases such as cancer and develop drugs to combat them.

Bending DNA costs less energy than assumed

more information:
Aghil Soman et al, Vertical structure of human telomeric chromatin, temper nature (2022). DOI: 10.1038 / s41586-022-05236-5

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