DNA has an ‘alter ego’

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DNA, the twisty molecule of life, has an alter ego, a new study has revealed.
Researchers from the University of Michigan and the University of California have also found that on rare occasions, its building blocks “rock and roll”, deforming the familiar double helix into a different shape.
“We show that the simple DNA double helix exists in an alternative form — for one per cent of the time — and that this alternative form is functional. Together the data suggest that there are multiple layers of information stored in the genetic code,” said Hashim M. Al-Hashimi, who led the study.
By adapting nuclear magnetic resonance technology, the researchers were able to observe transient, alternative forms in which some steps on the stairway come apart and reassemble into stable structures.
The question was, what were these alternative stable structures?
“Using NMR, we were able to access the chemical shifts of this alternative form. These chemical shifts are like fingerprints that tell us something about the structure,” co- researcher Evgenia Nikolova said.
Through careful analysis, the researchers realised the “fingerprints” were typical of an orientation in which certain bases are flipped 180 degrees. “It’s like taking half of the stairway step and flipping it upside down so that the other face now points up. If you do this, you can still put the two halves of the step back together. We took new solution NMR methods that previously have been used to study rare deformations in proteins and adapted them so that they could be used to study rare states in nucleic acids. Now that we have the right tools to look at these so-called excited states, we may find other short-lived states in DNA and RNA,” Al-Hashimi said. The findings have been published in the Nature journal.