Effects of SCR7 derivatives on nick ligation by LigI, LigIIIα/XRCC1 and LigIV/XRCC4 using radioactively-labeled nicked DNA substrate. DNA ligation reactions with a nicked, fluorescent DNA substrate (0.2 pmol) were carried as described in Materials and Methods. LigI (0.1 pmol, Panel A), LigIIIα/XRCC1 (0.1 pmol, Panel B) and LigIV/XRCC4 (1.1 pmol, Panel C) were incubated with SCR7 derivatives; SCR7-G (triangle); SCR7-R (circle); SCR7-X (square). Data are the mean ± standard deviation of three independent experiments.