Figure 4.

The appearance of UmuD and UmuD′ in response to DNA damage are temporally regulated by RecA, and the timing of the peak production of UmuD′ depends on the amount of DNA damage the cells have suffered. Immunoblot analyses were used to measure steady-state levels of UmuD and UmuD′ at various times after exponentially growing cultures of GW2771 [lexA⁺, recA⁺, umuD⁺ umuC⁺] were irradiated with UV(20 J/m² or 50 J/m²). The positions of UmuD (D), UmuD′ (D′) and a crossreacting species (CR), which was used as a loading control, are indicated.