Folding of a Stable DNA Motif Involves a Highly Cooperative Network of Interactions

Ellen M. Moody, Philip C. Bevilacqua

Research output: Contribution to journalArticle

58 Scopus citations

Abstract

Hairpins are structural elements that play important roles in the folding and function of RNA and DNA. The extent of cooperativity in folding is an important aspect of the RNA folding problem. We reasoned that an investigation into the origin of cooperativity might be best carried out on a stable nucleic acid system with a limited number of interactions, such as a stable DNA hairpin loop. The stable d(cGNAg) hairpin loop motif (closing base pair in lower case; loop in upper case; N = A, C, G, or T) is stabilized through only three interactions: two loop-loop hydrogen bonds in a sheared GA base pair and a loop-closing base pair interaction. Herein, we investigate this network of interactions and test whether the loop-loop and loop-closing base pair interactions communicate. Thermodynamic measurements of nucleotide analogue substituted oligonucleotides were used to probe the additivity of the interactions. On the basis of double mutant cycles, all interactions were found to be nonadditive and interdependent, suggesting that loop-loop and loop-closing base pair interactions form in a highly cooperative manner. When double mutant cycles were repeated in the absence of the other interaction, nonadditivity was significantly reduced suggesting that coupling is indirect and requires all three interactions in order to be optimal. A cooperative network of interactions helps explain the structural and energetic bases of stability in certain DNA hairpins and paves the way for similar studies in more complex nucleic acid systems.

Original languageEnglish (US)
Pages (from-to)16285-16293
Number of pages9
JournalJournal of the American Chemical Society
Volume125
Issue number52
DOIs
StatePublished - Dec 31 2003

All Science Journal Classification (ASJC) codes

  • Chemistry(all)

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