Figure 2.

Construction and function of target repressors. The λ cI repressor consists of a DNA-binding domain (Db), a flexible linker (Lk), and a dimerization domain (Dz). The site of recA-mediated cleavage was altered (A-G to A-R) to create a unique site for the insertion of target proteolytic processing sites (cI.Bss). (A) Cells expressing cI.WT or cI.Bss from the indicated promoters were infected with λ in the absence or presence of mitomycin C (32). After 15 min, the cells were washed, resuspended in LB/0.2% maltose/10 mM MgSO₄, and incubated for 5 hr. The resulting phage supernatants were titered as described. The progeny virus (pfu/μl) is shown for each repressor strain in comparison to an infection of cells that do not express a repressor. (B) HIV target repressors contain the GAG-POL site 1 (cI.HIV) or a mutant site (cI.HIVmt). A Western blot of cells expressing the WT and recombinant repressors from the Prm promoter using anti-cI sera. (C) Repressor function was determined by infection of strains expressing the repressors at subsaturation levels (2X promoter). (-), cells that do not express repressor.