Aptameric inhibition of in vitro DNA polymerization by phosphorothioate oligonucleotides.

DNA polymerization in the presence of phosphorothioate oligonucleotides (S-oligomers) was investigated. Oligonucleotides consisting of three or four consecutive guanosine residues (G4 and G3, respectively) inhibited chain elongation by AMV reverse transcriptase or Sequenase (polymerase function of T7 DNA polymerase). S-oligomers bearing G4 caused greater inhibition of chain elongation by both enzymes than those with G3. AMV reverse transcriptase was more susceptible to S-oligomers bearing consecutive guanosines than was Sequenase. Electrophoresis on a polyacryl amide gel revealed that G4 and G3-oligomers formed high-order polymeric complexes, and that S-oligomers with G4 formed much more complex than those with G3.