Primitive Molecule May Hold Key to Evolution of DNA and Early Life on Earth

DNA may hold the building blocks to life, but there may have been a simpler, more primitive form of the molecule in the ancient past. John Chaput, a researcher at Arizona State University's Biodesign Institute, has now shown that DNA sequences can be transcribed into a molecule known as TNA and reverse transcribed back into DNA using enzymes.

TNA is an unusual nucleic acid molecule, a class of molecules known as xenonucleic acids or XNAs. These molecules can potentially be developed into aptamers, which are molecular structures that can mimic the properties of naturally occurring polymers. This property has a wide range of applications when it comes to the development of drugs for the treatment of diseases.

Chaput and his team demonstrated that certain commercially available enzymes can help transcribe DNA sequences into TNA. What was more fascinating, though, was that under the right circumstances, the researchers were able to cause the TNA sequences to "evolve." The process that the researchers utilized for this sort of evolution was known as in vitro selection.

In order to accomplish this goal, researchers produced large pools of TNA molecules from DNA templates. They then exposed these molecules to a certain molecular target. The scientists extracted the TNA strands that could bind with the target and reverse-transcribed back into DNA. This DNA was then amplified using polymerase chain reaction (PCR).

After performing the experiment, the scientists found that the process could be repeated; this allowed for significant enrichment of the desired aptamer. In fact, they found a 380-fold enrichment from an original library of DNA templates.

So what does this mean? The research has helped pave the way for more sophisticated manipulation of TNA and other xenonucleic acids, which could greatly help in the development of drugs and the treatment of diseases. It also shows that TNA may have preceded RNA as a "stepping stone" molecule in the creation of life.

"TNA is resistant to nuclease degradation, making it an ideal molecule for many therapeutic and diagnostic applications," Chaput said in a press release.

The findings are published in the Journal of the American Chemical Society.