FIGURE 8.

Two additional downstream inhibitory elements can inhibit ARG8^m translation at both the COX2 and COX3 loci and are suppressed by the presence of the positive element within the COX2 leader peptide coding sequence. (A) Constructs were created as shown in which either codons 22–45, which contain the predicted codon 22–44 stem-loop, or codons 46–75, which contain the predicted codon 46–74 stem-loop, were isolated from other COX2 coding sequences and inserted either at the COX2 or COX3 locus. ARG8^m, COX2 codons, and deleted regions are diagrammed as in Figure 1 ▶. Growth of control prototrophic (cox2(1,89–91)::ARG8^m) and auxotrophic (cox2(1,15–25,89–91)::ARG8^m) strains on medium containing (+Arg) or lacking (−Arg) arginine are shown at the top for comparison. Strains shown, from top to bottom: at COX2: EHW154, EHW155, EHW358, and EHW357; and at COX3: EHW335, EHW336, EHW378, and EHW379 (Table 1 ▶). (B) The full leader peptide coding sequence (“+2–14”), only codons 2–6 encoding much of the positive element (“+2–6”; Bonnefoy et al. 2001), or an inactive version of the positive element within codons 2–6 (“+2–6*”; Bonnefoy et al. 2001) were introduced in front of the isolated codon 22–44 and 46–74 inhibitory sequences at COX2. ARG8^m, COX2 codons, and deleted regions are diagrammed as in Figure 1 ▶. Strains shown, from top to bottom: EHW412–EHW414 and EHW409–EHW411 (Table 1 ▶).