Figure 2.

(A) Uncleaved UmuD and UmuC regulate growth in response to DNA damage in exponentially growing E. coli cultures. Effect of various plasmid-encoded umuD⁺ umuC⁺ gene products on growth of GW8023 [lexA⁺, recA⁺, Δ(umuDC)595∷cat] after UV irradiation (25 J/m²). (□) ΔumuDC [pBR322kan]; (▴) umuD⁺ umuC⁺ [pSE117]; (●) umuD(S60A) umuC⁺ [pTO4] (this work). (B) The resistance to killing by DNA damage provided by uncleaved UmuD and UmuC depends on nucleotide excision repair. Survival after UV irradiation of isogenic strains of GW8101 [recA⁺ Δ(umuDC)595∷cat lexA⁺ uvrA6] (this work) that differ in the genotype of umuD and umuC carried on a plasmid: (■) umuD⁺ umuC⁺ [pSE117] (25); (▵) umuD′ umuC⁺ [pGW3751] (56); (▴) umuD(S60A) umuC⁺ [pTO4] (this work); (□) ΔumuDC [pBR322kan] (20).