Parasitic DNA multiplies in aging tissues
The genomes of all organisms, without exception, abound with fragments of so–called "parasitic DNA" - retrotransposons, which, in the absence of suppressive mechanisms, are repeatedly copied and distributed throughout the genome, which can have a negative impact on health.
Earlier, Brown University researchers working under the guidance of associate Professor Jill Kreiling demonstrated that the ability of retrotransposons to get out of control of the genome and be copied repeatedly gradually increases when human cells are cultured in the laboratory.
Their latest experiments on mice have shown that the same thing happens in the tissues of aging animals and in malignant tumors. Moreover, it turned out that these manifestations can be partially neutralized with a low-calorie diet.
To date, experts have not come to a consensus on whether the proliferation of retrotransposons in the body is an exceptionally harmful phenomenon. However, there is evidence that the genome is trying to "hide" retrotransposons by tightly packing inside heterochromatin protein structures.
As part of the work, the authors analyzed the state of the genomes of liver cells and skeletal muscles of mice aged 5, 24 and 36 months. It turned out that, in general, the DNA of these cells becomes more heterochromatin as the animals age. However, paradoxically, some regions characterized by the content of a large number of retrotransposons, on the contrary, are released from heterochromatin. This is especially pronounced after the animals reach the age of two, which for humans corresponds to about 70 years.
The described changes in the DNA configuration were accompanied by an increase in the expression of retrotransposons, as well as their copying and distribution throughout the genome. For example, in the period from 24 to 36 months of age, the number of copies of the retrotransposon “MusD” in the liver cells of mice increased by more than 2 times
Further experiments showed that the content on a balanced low-calorie diet (containing 40% fewer calories than the standard diet) significantly suppressed the proliferation of retrotransposons. The ability of a low-calorie diet to mitigate the manifestations of aging has been demonstrated in various animal models.
On the other hand, it turned out that some retrotransposons are expressed in large quantities in tissue cells affected by malignant diseases, such as lymphoma and hepatocellular carcinoma.
According to the authors, there is no evidence yet that retrotransposons can be a causal cause of cancer development. To date, only the existence of an associative relationship has been proven. In any case, the researchers plan to study the effect of retrotransposon proliferation on health, as well as the possibility of using drugs that suppress it to slow down the aging of the body and prevent age-related diseases.
Article by Marco De Cecco et al. Transposable elements become active and mobile in the genomes of aging mammalian somatic tissues published in the journal Aging.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of Brown University:
Parasitic DNA proliferates in aging tissues.
23.12.2013