Figure 7.

DNA synthesis by human Pol ι on templates containing UV photoproducts. (A) A ³²P-labeled 15mer primer was annealed to a DNA template containing a TT dimer or a TT (6–4) photoproduct right before the modified TT sequence. DNA polymerase assays were then performed with 37 ng (463 fmol) purified human Pol ι and 50 fmol DNA using dATP (A), dCTP (C), dTTP (T) and dGTP (G) individually or all four dNTPs (N₄). Lane 1, DNA synthesis on the template containing a TT dimer; lanes 2–6, DNA synthesis on the template containing a TT (6–4) photoproduct. (B) Translesion synthesis opposite the TT dimer was extended to 30 min and the reaction temperature shifted to 37°C, using 2-fold higher concentrations (100 µM) of a single dNTP or all four dNTPs as indicated. Human Pol ι in the reaction was increased to 50 ng (625 fmol). Quantitation of extended primers is shown at the bottom of the gel. DNA size markers in nt are indicated on the right.