FIG 3.

NHC-TP does not cause immediate chain termination. Primer extension reaction mixtures contained 10 nM P/T (shown at the top) and 20 nM POLRMT, and the reactions were performed in the presence of 1 μM ATP as the first ribonucleotide and increasing concentrations (in micromolar) of CTP, 3′-dCTP (top panel) or NHC-TP (bottom panel). The products were resolved by denaturing PAGE. The identity and concentration of the tested analog is indicated under each lane. The migrations of the primer (pr.) and the ribonucleotide extension products +1 to +4 are indicated on the left, and the intended nucleotide identities at each position are indicated on the right. The lane labeled “prim.” in the top panel contains unextended primer only. In the bottom panel, the location of the +2 and +3 positions are inverted due to the compression effect (indicated by a double-headed arrow).