Gap-filling DNA replication by pol V and pol III holoenzyme. Gap-filling replication was performed with pol V (MBP-UmuC) in the presence of UmuD′, RecA, and SSB, or with pol III holoenzyme, by using gapped pOC2 as a substrate. Reactions were performed in parallel in the presence and the absence of radiolabeled dTTP at 37°C for 20 min. Reaction products were fractionated by agarose gel electrophoresis and visualized by ethidium bromide staining (Left) or phosphorimaging (Right). Based on the analysis of the phosphorimage, the amount of radiolabel incorporated into DNA by pol V was 29.4% of the amount incorporated by pol III holoenzyme. FI, supercoiled plasmid; FII, open, circular plasmid; FIII, linearized plasmid; FIV, covalently closed and relaxed plasmid; GP, gapped plasmid.