Differential discrimination of DNA polymerase for variants of the non-standard nucleobase pair between xanthosine and 2,4-diaminopyrimidine, two components of an expanded genetic alphabet

Nucleic Acids Res. 1996 Apr 1;24(7):1308-13. doi: 10.1093/nar/24.7.1308.

Abstract

Mammalian DNA polymerases alpha and epsilon, the Klenow fragment of Escherichia coli DNA polymerase I and HIV-1 reverse transcriptase (RT) were examined for their ability to incorporate components of an expanded genetic alphabet in different forms. Experiments were performed with templates containing 2'-deoxyxanthosine (dX) or 2'-deoxy-7-deazaxanthosine (c7dX), both able to adopt a hydrogen bonding acceptor-donor-acceptor pattern on a purine nucleus (puADA). Thus these heterocycles are able to form a non-standard nucleobase pair with 2,4-diaminopyrimidine (pyDAD) that fits the Watson-Crick geometry, but is joined by a non-standard hydrogen bonding pattern. HIV-1 RT incorporated d(pyDAD)TP opposite dX with a high efficiency that was largely independent of pH. Specific incorporation opposite c7dX was significantly lower and also independent of pH. Mammalian DNA polymerases alpha and epsilon from calf thymus and the Klenow fragment from E. coli DNA polymerase I failed to incorporate d(pyDAD)TP opposite c7dX.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Cattle
  • DNA-Directed DNA Polymerase / metabolism*
  • Escherichia coli / enzymology
  • Hydrogen Bonding
  • Hydrogen-Ion Concentration
  • Molecular Sequence Data
  • Oligodeoxyribonucleotides / chemistry
  • Pyrimidines / metabolism*
  • Ribonucleosides / metabolism*
  • Substrate Specificity
  • Templates, Genetic
  • Xanthines

Substances

  • Oligodeoxyribonucleotides
  • Pyrimidines
  • Ribonucleosides
  • Xanthines
  • 2,4-diaminopyrimidine
  • xanthosine
  • DNA-Directed DNA Polymerase