Figure 1. Substrate specificity of yNtg1p and yNtg2p on oligonucleotides containing a DHU lesion. (A) 100 fmol of 5′-³²P-labeled duplex DHU-19/A (lanes 1–3), DHU-20/G (lanes 4–6) and DHU/AG (lanes 7–9) were incubated with 40 ng of yeast yNtg1p or yNtg2p at 37°C for 30 min in a standard reaction mix. Lane 1, control, DHU-19/A; lane 2, DHU-19/A + yNtg1p; lane 3, DHU-19/A + yNtg2p; lane 4, control, DHU-20/G; lane 5, DHU-20/G + yNtg1p; lane 6, DHU-20/G + yNtg2p; lane 7, control, DHU/AG; lane 8, DHU/AG + yNtg1p; lane 9, DHU/AG + yNtg2p. Arrows indicate the positions of 5′-³²P-labeled 18mer and 19mer standards. (B) 100 fmol of 3′-³²P-labeled duplex DHU-19/A (lanes 1–3), DHU-20/G (lanes 4–6) and DHU/AG (lanes 7–9) were incubated with 40 ng of yeast yNtg1p or yNtg2p at 37°C for 30 min in a standard reaction mix. Lane 1, control, DHU-19/A; lane 2, DHU-19/A + yNtg1p; lane 3, DHU-19/A + yNtg2p; lane 4, control, DHU-20/G; lane 5, DHU-20/G + yNtg1p; lane 6, DHU-20/G + yNtg2p; lane 7, control, DHU/AG; lane 8, DHU/AG + yNtg1p; lane 9, DHU/AG + yNtg2p. Arrows indicate the positions of 3′-³²P-labeled 12mer and 13mer standards. (C) A scheme describing the ability of yNtg2p to further remove the DHU lesion remaining on the 5′-terminus.