Wouldn’t you know, jumping “junk DNA” can be lethal too

artist’s image of double helix/Public Domain

Researchers Nigel Goldenfeld and Thomas Kuhlman noticed that “half of the human genome is made up of retrotransposons [jumping genes, “junk DNA”], but bacteria hardly have them at all” and wondered what would happen if they just inserted some:

“We thought a really simple thing to try was to just take one (retrotransposon) out of my genome and put it into the bacteria just to see what would happen,” Kuhlman said. “And it turned out to be really quite interesting.”

Their results, published in the Proceedings of the National Academy of Sciences, give more depth to the history of how advanced life may have emerged billions of years ago—and could also help determine the possibility and nature of life on other planets.

Along the way to explaining life, the researchers first encountered death—bacterial death, that is. When they put retrotransposons in bacteria, the outcome was fatal.

“As they jump around and make copies of themselves, they jump into genes that the bacteria need to survive,” Kuhlman said. “It’s incredibly lethal to them.”

When retrotransposons copy themselves within the genome, they first find a spot in the DNA and cut it open. To survive, the organism then has to repair this cut. Some bacteria, like E. coli, only have one way to perform this repair, which usually ends up removing the new retrotransposon. But advanced organisms (eukaryotes) have an additional “trick” called nonhomologous end-joining, or NHEJ, that gives them another way to repair cuts in their DNA.

Goldenfeld and Kuhlman decided to see what would happen if they gave bacteria the ability to do NHEJ, thinking that it would help them tolerate the damage to their DNA. But it just made the retrotransposons better at multiplying, causing even more damage than before.

“It just completely killed everything,” Kuhlman said. “At the time, I thought I was just doing something wrong.” More” at Phys.org

You are doing something wrong, Dr. Kuhlman. You are tinkering with an engineered system whose manual you have never read, though you may end up contributing to it.