Stress and transposons
Scientists talked about the role of "jumping genes" in stress
Polina Gershberg, Naked Science
Transposons, or "jumping genes" are non–coding sequences of nucleic acids that can suddenly change their location in the genome or create their own copies. Initially, they were considered as some kind of genetic garbage, but gradually it turns out that transposons play an important role in the functioning of the body.
In a study published in the Proceedings of the National Academy of Sciences (Hernandez el al., B2 and ALU retrotransposons are self-cleaving ribozymes whose activity is enhanced by EZH2), a group of scientists from the United States tried to understand how such "jumping genes" work under stress. We are talking about the so-called Alu elements, which make up approximately 10.7% of the entire human genome.
Fluorescent in situ hybridization of human chromosomes (contrasted in red) with probes to Alu repeats (green).
Chromosomal rearrangements associated with Alu elements can cause some forms of cancer and hereditary diseases.
Scientists have found that Alu elements in humans and mice (in the rodent genome they are labeled as B2 elements) are intensively expressed when the body is under stress. The RNA product of their transcription is subsequently cut when interacting with the regulatory protein Pzh2. However, the mechanism of this cutting was unclear to researchers until recently, because Pzh2 is not a nuclease, an enzyme that catalyzes the degradation of RNA and DNA.
A new study has shown that the products of Alu and B2 elements are not just RNA, but ribozymes, nucleic acids with enzymatic properties. Moreover, these ribozymes catalyze their own cleavage. The products of this catalytic cleavage are released from chromatin and activate the synthesis of heat shock proteins. Protein Pzh2 significantly accelerates the process of autocatalysis, giving ribozymes a working conformation (spatial arrangement of atoms in the molecule).
According to the authors of the study, the transcription products of the Alu and B2 sequences can be called "epigenetic ribozymes", which function as transcription switches during stress. This is a very convenient mechanism for the cell to activate the response to stress, since no synthesis of new intermediate gene products occurs with it.
The results of the work can have not only theoretical, but also practical significance. Further study of the role of transposons in stress reactions will help to understand how to direct the body's work in the right direction, for example, during the development of infections, cancer or autoimmune diseases.
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