Figure 3.

Uncleaved UmuD and UmuC regulate DNA synthesis in response to DNA damage. The effect of various umuD umuC gene products on inhibition and recovery (IRR) of DNA synthesis caused by UV irradiation in isogenic strains of GW8024 [lexA(Def) recA⁺ Δ(umuDC)595∷cat] that differ in the genotype of umuD umuC carried on a plasmid. The rate of DNA synthesis (amount of [³H]thymidine incorporated into TCA insoluble counts during a 2-min pulse; ■) and OD₆₀₀ (▵) were measured at various times before and after UV irradiation (indicated by arrow) in isogenic strains that differ only in the genotype of umuD umuC carried on a plasmid: (A) ΔumuDC [pBR322kan] (20); (B) umuD⁺ umuC⁺ [pSE117] (25); (C) umuD′ umuC⁺ [pGW3751] (56); (D) umuD(S60A) umuC⁺ [pTO4] (this work); (E) umuD⁺ umuC125 [pLM109] (21).