Knot-shaped DNA found in living cells for the first time

Few people know that in addition to the classic double helix, discovered in 1953, DNA can take other forms. The discoverers of DNA, Watson and Crick, did not report this, because they were not sure that these were real molecules, and not just "junk", scraps of larger chains. Recently, however, the Garvan Institute for Medical Research has created a tool that has made it possible to get to the truth. For example, it is well established that there is DNA in the form of a knot. But what is her role?

Information about the structure of a living organism in DNA is encoded not only by a unique sequence of nucleotides, but also by the shape of the molecule itself. The shape of the chain determines how it contacts the RNA, how the information written in it will be "read". And from this point of view, the "i-motif" structure, a knot of four nucleotide chains, raises many questions. Here, the C nucleotides on the same strand are linked to each other, while in the helix they always interact with the G nucleotide - and then only on the opposite strand.

If the DNA helix exists stably, then the i-motif tends to disappear and reappear. Australian scientists have created a fragment of an antibody molecule that can only interact with i-motif and, upon contact, triggers a fluorescence reaction. Then, studying the order in which green spots appeared on the medium under study, they began to study patterns. It is believed that i-motifs are activated at key moments in the life of DNA and can “turn on” and “turn off” individual genes.

It has already been proven that nodal DNA lives in telomeres, protective caps at the ends of chromosomes, which play a major role in biological aging of the body. And they are active during the last phase of the cell's life cycle, during the reading of DNA to create a new cell. But what exactly does i-motif do, scientists cannot yet answer - they are aware of themselves on the verge of discovery, but the research is far from complete.