FIGURE 1.

Extension opposite N²-ethyl-Gua or Gua by DNA Pol ι in the presence of MgCl₂ or MnCl₂. Primer extension assays were carried out as described under “Experimental Procedures.” The annealed primer (12-mer) and templates containing either N²-ethyl-Gua or Gua (A) were incubated with 10 nm DNA pol ι and increasing concentrations of MgCl₂ (B) or MnCl₂ (C). Maximal primer extension was observed at 2 mm MgCl₂ and 0.075 mm MnCl₂. In single nucleotide extension reactions with only dTTP or dCTP using the 14-mer primer, the 15-mer product of dTMP insertion migrates to the position of the upper band and the 15-mer product of dCMP insertion migrates to the position of the lower band (data not shown).