FIGURE 1.

Vectors expressing luciferase used to study the programmed −1 ribosomal frameshift of HIV-1 group M in vitro and in cultured cells. (A) The frameshift region of subtype B was inserted upstream of the coding sequence of the luciferase reporter gene, which is under control of a CMV and a T7 promoter, generating pLUC/HIV/B (−1). The classic structure of the frameshift stimulatory signal is represented here. For the study of all subtypes of group M and mutants of subtype B, the corresponding vectors were constructed by exchanging the Eco47III–BamHI fragment of pLUC/HIV/B (-1) with an appropriate oligonucleotide cassette. For the (-1) constructs, the luciferase sequence is in the −1 reading frame relative to the AUG initiation codon, so that a −1 frameshift is required to produce luciferase. An adenine nucleotide was added between the frameshift region and luciferase sequence for the (0) constructs, so that luciferase is expressed by ribosomes that do not shift the reading frame. (B) Sequences of the frameshift region of all of the constructs used in this study. Nucleotides modified or deleted relative to subtype B are underlined or represented by broken lines, respectively.