Figure 4.

DNA synthesis of pol β WT, pol β K72A, and pol β H34G during BER of a native abasic site in TNR tracts. The DNA synthesis activities of pol β WT and pol β dRP lyase mutant, K72A and H34G during BER were characterized with the (GAA)₂₀ (A) or (CAG)₂₀ (B) repeat substrate containing a native abasic site as described in the Materials and Methods. Lane 1 represents the substrate only. Lane 2 indicates the reaction mixture with 1 U UDG and 25 nM APE1. Lanes 3 and 4 correspond to the reaction mixture with 10 nM pol β K72A in the absence and presence of 25 nM FEN1. Lanes 5 and 6 correspond to the reaction mixture with 10 nM pol β K72A and 25 nM LIG I in the absence and presence of 25 nM FEN1. Lanes 7 and 8 correspond to the reaction mixture with 10 nM pol β H34G in the absence and presence of 25 nM FEN1. Lanes 9 and 10 correspond to the reaction mixture with 10 nM pol β H34G and 25 nM LIG I in the absence and presence of 25 nM FEN1. Lanes 11 and 12 correspond to the reaction mixture with 10 nM pol β WT in the absence and presence of 25 nM FEN1. Lanes 13 and 14 correspond to the reaction mixture with 10 nM pol β WT and 25 nM LIG I in the absence and presence of 25 nM FEN1. Substrates were ³²P-labeled at the 5′-end of the damaged strand and are illustrated above each gel. The experiments were repeated at least three times. Representative gels are illustrated.