According to a new study, DNA’s ability to “shape-shift” found it becoming the blueprint of life rather than self-replicating strands of RNA. This shape-shifting was recently discovered following the investigation of DNA at an atomic level.

DNA RNA
Image source: Wikimedia Commons

Study Looks At DNA evolution

The details of the study lead by Biochemist Hashim Al-Hashimi of Duke University was published this week in Nature Structural & Molecular Biology.

The study, while speculative, suggests that this ability to change its shape, added to the resiliency of DNA is part and parcel related to a structure discovered in the 1960s by Karst Hoogsteen called the Hoogsteen base pair.

The Hoogsteen base pair is not easy to study as they are quite elusive to researchers. Base pairs rarely form a Hoogsteen pair (about 1% of the time) and consequently are difficult to study.

However, when they do appear, it’s these pairs that are responsible for the double helix completely changing directions and, by proxy, the shape of DNA. Essentially, a Hoogsteen based pair “flips over” the nucleic acid.

“It becomes this very dynamic entity,” Al-Hashimi said. “You can just imagine the molecule dancing around.”

The Hoogsteen base pairs move to limit the damage, something that RNA cannot do when a methyl group is added to an RNA strand. Instead, RNA simply becomes unraveled or destroyed. Adding a methyl group, according to Al-Hashimi, was like “dropping a nuclear bomb on the helix.”

As a result of this inability to from Hoogsteen pairs, Al-Hashimi believes that RNA was evolutionary regulated to the role of “messenger” while DNA became the repository of for the blueprint for life as we know it.

“If our genomes were made up of RNA, there’s a very good chance that they wouldn’t be able to sustain chemical damage that’s inflicted on them all the time,” Al-Hashimi said. “It seems like DNA’s ability to absorb damage is one reason why we evolved DNA-based genomes.

This explanation is “still speculative,” he continued when asked about his certainty of how DNA came to be the depository, “since we can’t travel back in time.”

“It seems that nature has exploited the inability of RNA to absorb damage to create this molecular switch,” he said. “By methylating the RNA you can increase production of proteins.”