Figure 5.

Catalytically inactive Lig4/XRCC4/XLF promotes Lig3-mediated joining of blunt DNA ends in vitro. The capacity for catalytically inactive Lig4/XRCC4 to promote ligation by Lig3 (A), or Lig1 (B) was assessed by incubating a blunt DNA ligation substrate (linearized pUC19, 2.7 kb) with purified recombinant proteins as indicated at the following concentrations: Ku, 250 nM; XLF, 200 nM; Lig4/XRCC4, 500 nM; Lig3/XRCC1, 40 nM; and Lig1,180 nM. Reactions (10μl) containing 50 ng of linear DNA were incubated for 30 minutes at room temperature, deproteinized, analyzed by agarose gel electrophoresis. Bar graph represents six independent experiments and error bars represent SD.