Figure 4.

Long-patch BER. STEP 1 and 2 are the same as in Figure 2. An oxidized abasic site which is known to require LP-BER, 2-deoxyribonolactone, is shown. Pol β, δ, or ε inserts multiple nucleotides at the 3′-OH nick site generated by APE1 (STEP 3; we show insertion of three G’s (blue)). FEN1 removes the 5′-flap (STEP 4), and Lig1 seals the nick in the backbone (STEP 5).