Rebooting DNA

We’re always being told to back up the data on our hard drives in case of a crash. Now, in one of the most surprising developments to emerge from genetics in years, researchers at Purdue University are reporting that some organisms may carry around a complete backup copy of their own genomes. The copy is apparently called into action to replace sections of DNA that have, in effect, crashed–meaning they have mutated beyond the point where normal DNA repair mechanisms are effective.

IANAB – I Am Not A Biologist – but the finding, reported online yesterday in the journal Nature, could turn out to be a Nobel-caliber breakthrough. Even the Purdue researchers’ colleagues and competitors are calling the results “spectacular,” a word not often heard in scientific circles.

In essence, a team of researchers led by Robert E. Pruitt and Susan J. Lolle of Purdue found that Arabidopsis plants (a type of mustard weed) that inherited defective copies of a gene called Hothead from both parents were able to “revert” to the correct gene as they developed. Since the correct gene sequence was not present in the plants’ own chromosomal DNA, but had been present in the DNA of previous generations, the researchers believe that Arabidopsis must store stable copies of Hothead and other genes outside its genome–perhaps in a heretofore-unknown form of RNA, the molecule that translates DNA’s genetic instructions into functioning proteins. Veteran science journalist Nicholas Wade does a great job of explaining the discovery in today’s New York Times.

Pruitt told Wade that the finding was a “complete shock.” The researchers haven’t determined whether the gene-correction phenomenon occurs in other organisms, how the backup information is stored, or how it interacts with chromosomal DNA. But if the recent history of molecular biology is any guide, it would be very unusual if such a useful mechanism were confined only to Arabidopsis. (The species happens to be a favorite experimental subject for plant geneticists because of its relatively small genome and its rapid reproduction cycle.) The finding is sure to touch off a race to uncover such mechanisms in other species, including humans.