The structure of telomeric DNA was revealed by researchers using the laws of physics and a small magnet. Some people believe that telomeres hold the secret to prolonging life. Although they shrink a little with each cell division, they protect genes from harm. If they get too small, the cell will perish. Thanks to the new finding, we will learn more about disease and aging.
Physics is not the first branch of science that comes to mind when the subject of DNA is brought up. But one of the researchers who discovered the new DNA structure is John van Noort of the Leiden Institute of Physics (LION). He is a biophysicist who conducts biological studies using physics techniques. Biologists at the Nanyan University of Technology in Singapore were also interested in this issue. They published the results in the renowned journal Nature.
Our chromosomes, which contain the genes that determine our traits, are found in every cell of our body (for example, how we look). Telomeres, which protect chromosomes from damage, are located at the ends of these chromosomes. In some ways they resemble aglets with plastic shoelace ends.
In order for DNA to fit inside the cell, it must be folded because it is two meters long between telomeres. This is accomplished by wrapping packages of protein and DNA together to form a structure known as the nucleosome. A nucleosome, a piece of free (or unbound) DNA, a nucleosome, and the like are lined up in a bead-like pattern.
The string of beads then contracts further. The length of DNA between the nucleosomes (beads in the array) determines how it achieves this. There were already two known structures after folding. One of them has free DNA suspended in the space between two nearby beads sticking together (Figure 2A). Nearby beads cannot bind together if the DNA gap between them is too small. Then two piles begin to form next to each other (fig. 2B).
Van Noort and colleagues discovered an additional telomere structure in their research. Here, there is no more free DNA between the beads, as the nucleosomes are much closer together. Ultimately, this forms a single large DNA helix or spiral (Figure 2C).
The new structure was found by combining electron microscopy and molecular force spectroscopy. The second method was developed in Van Noort's lab. Here, a small magnetic ball is attached to one end of the DNA and this ball is attached to a glass slide at the other end. The string of pearls is then smashed by a series of powerful magnets located on this ball. You can learn more about how the string is folded by counting how much force it takes to separate each bead. Singaporean researchers then used an electron microscope to better understand the structure.
Van Noort calls the structure "the holy grail of molecular biology." Knowing the structure of molecules will help us understand how genes are activated and inactivated and how cellular enzymes deal with telomeres as they repair and copy DNA. Our knowledge of the structural components in the body will increase with the discovery of the new telomeric structure. And ultimately this will help us understand aging, diseases like cancer, and develop drugs to treat them.