FIG. 8.

Adding an upstream, strong Kozak AUG codon in exon 2 of the env isoforms does not diminish Env expression. (A) Mutations in exon 2 of the env cDNA constructs that introduced either a strong Kozak AUG codon (KAUG) or the same mutations minus the AUG codon (KAGG). A UAA translation termination motif was included at codon 4 to avoid aberrant protein synthesis. (B) HeLa cells transfected with the env cDNA constructs, pCMVTat2X, pLTRrev1, and pEGFP were analyzed for Env and Vpu by immunoblotting and densitometry. The percentage of expression relative to that of the env5 construct (E5; set at 100%) is graphed. wt, wild type; E6, pDRenv6; E5KAGG and E6KAGG, env5 and env6 constructs without the Kozak AUG codon; E5KAUG and E6KAUG, env5 and env6 constructs with the Kozak AUG codon.