Untangled heterochromatin
Biologists have found out how unreadable genes are "read"
Nikita Shevtsev, Indicator
Russian biologists have found a mechanism that allows reading genes that are not available under normal conditions. This is possible due to the presence of sequences in the genome that blocker proteins recognize. The results obtained will help to better understand the mechanisms of protein expression. The researchers' article was published in the journal Scientific Reports (Funikov et al., Adaptation of gene loci to heterochromatin in the course of Drosophila evolution is associated with insulator proteins).
The genomes of the organisms containing the nucleus are linked into a structure that consists of DNA, RNA and binding proteins and is called chromatin. Chromatin can usually be divided into two main forms, which differ in the ability to read genetic information. The unreadable part – a tightly wound DNA strand on proteins – is called heterochromatin. Euchromatin consists of free sections of unwound DNA, and it can be read for the synthesis of proteins and RNA.
For a long time, researchers believed that heterochromatin is "silent", that is, it should not contain genetic information that affects the external signs of the body. As genomic data of various organisms were obtained, biologists showed that heterochromatin contains both inactive and active regions. The latter have genes that encode proteins, so the features of the structure of heterochromatin have become a new object for study. In particular, in drosophila, in areas of heterochromatin lying near the intersection of parts of chromosomes, researchers have already found several hundred protein-coding genes.
Scientists from MIPT and the V. A. Engelhardt Institute of Molecular Biology of the Russian Academy of Sciences investigated protein-coding genes that are located near the centromeres of chromosomes, in the so-called subcentromeric heterochromatin. Biologists have shown that insulators are located next to these genes – DNA sequences that bind special proteins that block the signal coming from the genomic environment.
The researchers analyzed the genes that moved between euchromatin and heterochromatin in fruit flies, whose species are separated by 40 million years of evolution. As a result of the analysis, it turned out that the DNA sequences recognized by the insulator proteins are preserved with almost all the studied genes, regardless of their location in different parts of the chromatin.
"We assume that the ability for local adaptation of genes in heterochromatin regions of the genome was predetermined by the content of insulator sites in the regulatory regions of these genes in their common ancestor. In addition, we have shown that the majority of heterochromatin genes are associated with not one, but many insulator proteins, which may compensate for each other's function and ensure their normal functioning in a heterochromatin environment," sums up one of the authors of the work, researcher at the Laboratory of Molecular Mechanisms of Biological Adaptation of the IMB RAS Sergey Funikov.
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