CHICAGO, Jan. 24 (Xinhua) -- A study at Washington University School of Medicine in St. Louis indicates that "jumping genes" -- bits of DNA that can move from one spot in the genome to another and are well-known for increasing genetic diversity over the long course of evolution -- play another and more surprising role of stabilizing the 3D folding patterns of the DNA molecule inside the cell's nucleus.
The study was published Friday in the journal Genome Biology.
Studying DNA folding in mouse and human blood cells, the researchers found that in many regions where the folding patterns of DNA are conserved through evolution, the genetic sequence of the DNA letters establishing these folds is not. It is ever so slightly displaced. But this changing sequence, a genetic turnover, does not cause problems. Because the structure largely stays the same, the function presumably does, too, so nothing of importance changes.
Jumping genes are also called transposable elements.
"We were surprised to find that some young transposable elements serve to maintain old structures," said the study's first author Mayank N.K. Choudhary, a doctoral student at the university. "The specific sequence may be different, but the function stays the same. And we see that this has happened multiple times over the past 80 million years, when the common ancestors of mice and humans first diverged from one another."
The fact that a new transposable element can insert itself and serve the same role as an existing anchor creates a redundancy in the regulatory portions of the genome, regions of the DNA molecule that determine how and when genes are turned on or off.
According to the researchers, this redundancy makes the genome more resilient. In providing both novelty and stability, jumping genes may help the mammalian genome strike a vital balance -- allowing animals the flexibility to adapt to a changing climate.
"Our study changes how we interpret genetic variation in the noncoding regions of the DNA," said senior author Ting Wang, a professor of medicine at the university. "For example, large surveys of genomes from many people have identified a lot of variations in noncoding regions that don't seem to have any effect on gene regulation, which has been puzzling. But it makes more sense in light of our new understanding of transposable elements - while the local sequence can change, but the function stays the same."
The researchers have uncovered another layer of complexity in the genome sequence that was not known before. "We may need to revisit these types of studies in light of the new understanding we now have of transposable elements," Wang said.
