Genome complexity: a different epigenetic code found (Introduction)

by David Turell @, Monday, February 28, 2022, 19:49 (759 days ago) @ David Turell

In rotifers:

https://phys.org/news/2022-02-scientists-dna-modification-animals-captured.html

"In humans and other eukaryotes, two principal epigenetic marks are known. A team from the Marine Biological Laboratory (MBL) has discovered a third, novel epigenetic mark—one formerly known only in bacteria—in bdelloid rotifers, small freshwater animals.

"We discovered back in 2008 that bdelloid rotifers are very good at capturing foreign genes," said senior author Irina Arkhipova, senior scientist in the MBL's Josephine Bay Paul Center. "What we've found here is that rotifers, about 60 million years ago, accidentally captured a bacterial gene that allowed them to introduce a new epigenetic mark that was not there before." This is the first time that a horizontally transferred gene has been shown to reshape the gene regulatory system in a eukaryote.

"'This is very unusual and has not been previously reported," Arkhipova said. "Horizontally transferred genes are thought to preferentially be operational genes, not regulatory genes. It is hard to imagine how a single, horizontally transferred gene would form a new regulatory system, because the existing regulatory systems are already very complicated."

"'It's almost unbelievable," said co-first author Irina Yushenova, a research scientist in Arkhipova's lab. "Just try to picture, somewhere back in time, a piece of bacterial DNA happened to be fused to a piece of eukaryotic DNA. Both of them became joined in the rotifer's genome and they formed a functional enzyme. That's not so easy to do, even in the lab, and it happened naturally. And then this composite enzyme created this amazing regulatory system, and bdelloid rotifers were able to start using it to control all these jumping transposons. It's like magic." (my bold)

***

"In the two previously known epigenetic marks in eukaryotes, a methyl group is added to a DNA base, either cytosine or adenine. The team's newly discovered mark is also a cytosine modification, but with a distinct bacterial-like positioning of the methyl group—essentially recapitulating evolutionary events of over two billion years ago, when the conventional epigenetic marks in early eukaryotes emerged.

***

"...the Arkhipova lab was surprised to find a gene in the rotifer genome that resembled a bacterial methyltransferase (a methyltransferase catalyzes the transfer of a methyl group to DNA). "We hypothesized that this gene conferred this new function of suppressing transposons, and we spent the last six years proving that, indeed, it does," Arkhipova said."

Comment: Note my bold. Appeared magically or by God's design?


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