In contrast, cells transfected with inactive protease (D25N) showed detectable GFP–PR, even in the absence of the drug (Figure 1c). This is due to the inability of this protease to excise itself from the fusion protein. The result for protease detection alone showed that visible protease, such as GFP–PR, was dependent on the drug concentration, protease resistance mutations and processing of the protease evaluated (Figure 1c). In addition, evaluation of the cellular translation factors eIF4GI and PABP showed proteolytic processing when the HIV-1 protease was not inhibited. In contrast, evaluation of the inactive PR-D25N showed its inability to cleave eIF4GI and PABP (Figure 1d). Those results show that the pattern of resistance mutations within the HIV-1 protease and the concentration of the protease inhibitor are able to modulate the translation of cellular proteins, suggesting that our phenotypic system is based on the ability of HIV-1 protease to cleave cellular translation factors