FIG. 3.

Proofreading nuclease assays of purified human Polι. (A) The DNA template and four primers used for nuclease activity assays. The primers were labeled with ³²P at their 5′ ends as indicated by an asterisk. Each primer was annealed individually to the template. (B) DNA substrates (50 fmol) containing annealed primers as indicated were incubated without (−) or with (+) purified human Polι (46 fmol) for 30 min at 30°C in the DNA polymerase assay buffer without dNTPs. Reaction products were separated by electrophoresis on a 20% denaturing polyacrylamide gel. DNA size markers in nucleotides are indicated on the right.