Table 3. Proofreading during TT dimer bypass using substrate D-3.

Substrate D-3 allows for detection of proofreading of errors introduced by Pol η at either the 3′ T or at the two preceding undamaged positions. Previous studies have shown that ∼75% of the dark blue plaques reflect misinsertion of G opposite the 3′ T of the TT dimer (13).