Figure 4.

Requirement for nucleotides for NHEJ in vitro. DSB substrates were incubated with HeLa whole cell extract as described in Materials and Methods. ATP and/or dNTP were added to the reactions to 4 mM and 100 µM concentrations, respectively, as indicated. Substrate DNA was recovered and transfected into E.coli to assess formation of circular monomeric end joining products as described in Materials and Methods. The number of plaques formed was measured and they were scored as blue or white. NHEJ activity is presented as the percentage of plaques compared to the complete reaction. The fraction of blue plaques is indicated in black and the fraction of white plaques in gray. H, negative control containing heated cell extract.