Figure 2. Gp67 Inhibits rRNA Synthesis In Vitro and In Vivo.

(A) Sequences of promoters used in subsequent experiments.

(B) Gp67 inhibits RNAP activity at Sau rrn promoters but not at a G1 phage –10/–35 promoter (pORF05). The indicated bands were quantified by phosphor-imagery; relative activity (versus holoenzyme alone) is denoted below each lane.

(C) Gp67 does not significantly decrease rRNA abundance in vivo. Cellular RNA was purified from 2 × 10⁸ Sau RN4220 cells at different times after the induction of gp67 synthesis. The Sau σ is either wild-type (WT) or the mutant (M) unable to interact with gp67 (Figure S1D).

(D) Gp67 inhibits synthesis of rRNA in vivo. Inducer was added to Sau RN4220 cells containing pRMC2 or pRMC2-gp67, and newly synthesized RNA was labeled by the addition of [³²P]-orthophosphoric acid to the growth medium. RNA was purified from 2 × 10⁸ pRMC2 and pRMC2-gp67 cells, run on a 6% urea-PAGE gel, stained with GelRed to visualize all RNAs (left), and visualized by phosphorimagery (right).

See also Figure S2.