Scientists find instructions in junk DNA

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

Russian molecular biologists have found that the junk DNA at the ends of chromosomes contains instructions for synthesizing a protein that helps cells not die from stress. Their findings were presented in the journal Nucleic Acids Research.

"This protein is interesting because it is found in RNA, which was previously considered non-coding, one of the" helpers "of telomerase. We discovered that it can have another function if it is not in the cell nucleus, but in its cytoplasm. telomerase can bring scientists closer to the creation of the "elixir of youth" and help in the fight against cancer, "said Maria Rubtsova from Lomonosov Moscow State University, whose words are reported by the press service of the university.

The key to immortality

The cells of the embryo and embryonic stem cells are virtually immortal from the point of view of biology - they can live almost indefinitely in an adequate environment, and divide an unlimited number of times. In contrast, cells in an adult's body gradually lose their ability to divide after 40-50 division cycles, entering the aging phase, which presumably reduces the chances of developing cancer.

These differences are due to the fact that each division of "adult" cells leads to a reduction in the length of their chromosomes, the ends of which are marked with special repeating segments, the so-called telomeres. When telomeres become too small, the cell "retires" and ceases to participate in the life of the body.

This never happens in embryonic and cancer cells, since their telomeres are renewed and lengthened with each division due to special telomerase enzymes. The genes responsible for the assembly of these proteins are "turned off" in adult cells, and in recent years scientists have been actively thinking about whether it is possible to extend the life of a person by forcibly turning them on or creating an artificial analogue of telomerases.

Rubtsova and her colleagues have long been studying how "natural" telomerases in humans and other mammals work. Recently, they were interested in why ordinary cells in the body, where this protein does not work, for some reason synthesize large quantities of one of its assistants, a short RNA molecule called TERC.

This sequence of about 450 "genetic letters", the biologist explains, was previously thought to be a common piece of "junk DNA" that telomerase copies and adds to the ends of chromosomes. For this reason, scientists did not pay much attention to the structure of TERC and the possible roles of this fragment of the genome in the life of cells.

Hidden assistant

Analyzing the structure of this RNA in human cancer cells, Rubtsova's team noticed that there is a special nucleotide sequence inside it, which usually marks the beginning of a protein molecule. Having found such a curious "piece", biologists checked whether there are analogues in the cells of other mammals.

It turned out that they were present in the DNA of cats, horses, mice and many other animals, and their structure of this fragment in the genome of each of these animals coincided by about half. This led geneticists to the idea that inside TERC there were not meaningless fragments of ancient genes, but a completely "living" protein.

They tested this idea by inserting additional copies of this RNA into the DNA of the same cancer cells and making them more actively read such regions. Additionally, the scientists conducted a series of similar experiments on E. coli, in whose genome there are no "classic" chromosomes and telomerases.

It turned out that telomerase RNA was actually responsible for the synthesis of special protein molecules, hTERP, which consisted of only 121 amino acids. Its increased concentration in cancer cells and microbes, as further experiments showed, protected them from various types of cellular stress, saving their lives in case of overheating, lack of food or the appearance of toxins.

The reason for this, as Rubtsova and her colleagues later found out, was that hTERP accelerates the process of "processing" scraps of proteins, RNA and other molecules in lysosomes, the main "incinerators" of the cell. This simultaneously protects them from death and significantly reduces the chances of mutations and the development of cancer.

Further experiments, according to geneticists, will help us understand how telomerase and hTERP interact with each other, and how they can be used to create a kind of "elixir of youth" that is safe from the point of view of oncology.