Figure 4

Mechanism of replicative homeostasis. At A, relatively high concentrations of Env_Wt (blue, A) favour high affinity Env:RNA_pol interactions out-competing variant forms (Env_mt, red), increasing RNA_pol processivity but reduced fidelity increasing relative output of variant RNAs. Subsequent ribosomal (R, mauve) translation increases concentrations Env_mt (red), relative to Env_Wt, returning the system to equilibrium. Relative excess Env_mt (B, red) out-compete Env_Wt (blue) for interactions with RNA_pol, favouring Env_mt:RNA_pol, and blocking Env_Wt:RNA_pol interactions. Env_mt:RNA_pol complexes relatively decrease RNA_polprocessivity but increase fidelity, increasing output of wild-type RNAs. Subsequent increased translation of Env_Wt relative to Env_mt restores the equilibrium.