DNA polymerase-mediated synthesis of unbiased Threose Nucleic Acid (TNA) polymers requires 7-deazaguanine to suppress G:G mispairing during TNA transcription

Matthew R. Dunn, Andrew C. Larsen, Walter J. Zahurancik, Nour Eddine Fahmi, Madeline Meyers, Zucai Suo, John C. Chaput

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

Threose nucleic acid (TNA) is an unnatural genetic polymer capable of undergoing Darwinian evolution to generate folded molecules with ligand-binding activity. This property, coupled with a nuclease-resistant backbone, makes TNA an attractive candidate for future applications in biotechnology. Previously, we have shown that an engineered form of the Archaean replicative DNA polymerase 9 N, known commercially as Therminator DNA polymerase, can copy a three-letter genetic alphabet (A,T,C) from DNA into TNA. However, our ability to transcribe four-nucleotide libraries has been limited by chain termination events that prevent the synthesis of full-length TNA products. Here, we show that chain termination is caused by tG:dG mispairing in the enzyme active site. We demonstrate that the unnatural base analogue 7-deazaguanine (7dG) will suppress tGTP misincorporation by inhibiting the formation of Hoogsteen tG:dG base pairs. DNA templates that contain 7dG in place of natural dG residues replicate with high efficiency and >99% overall fidelity. Pre-steady-state kinetic measurements indicate that the rate of tCTP incorporation is 5-fold higher opposite 7dG than dG and only slightly lower than dCTP incorporation opposite either 7dG or dG. These results provide a chemical solution to the problem of how to synthesize large, unbiased pools of TNA molecules by polymerase-mediated synthesis.

Original languageEnglish (US)
Pages (from-to)4014-4017
Number of pages4
JournalJournal of the American Chemical Society
Volume137
Issue number12
DOIs
StatePublished - Apr 1 2015

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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