(ORDO NEWS) — Scientists from the Marine Biological Laboratory (USA) have discovered a new DNA modification system in animals, which is inherited from bacterial microorganisms.
Until now, only two epigenetic marks have been known in humans and other eukaryotes that regulate gene activity during embryonic development.
An epigenetic mark has been identified in bdelloid or leech rotifers, which are known to be able to capture foreign genes. According to scientists, rotifers accidentally took over a bacterial gene about 60 million years ago, which led to the emergence of a new epigenetic regulatory mechanism.
This is the first time that a horizontally transferred gene has been shown to alter the gene regulation system in eukaryotes.
Hitherto it has been thought that horizontally transferred genes are preferably operational genes rather than regulatory genes. In bdelloid rotifers, the bacterial gene fused with the eukaryotic genome in such a way that it formed a DNA region that encodes a functional enzyme, methyltransferase, which regulates mobile genetic elements – transposons.
Transposons are capable of reproducing within the genome, damaging genes, so their control is necessary for the survival of cells and the organism as a whole. The presence of three epigenetic control marks leads to the fact that the content of transposons in bdelloid rotifers is lower than in other eukaryotes.
Two previously known epigenetic marks in eukaryotes are characterized by the addition of a methyl group (CH3) to cytosine or adenine.
The newly discovered team label is also a modification of cytosine, but the addition of the methyl group occurs in the same way as in bacteria. This recapitulates early evolutionary events over two billion years ago, when early eukaryotes developed their first epigenetic mechanisms.
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