Figure 1

Regulatory principles of retroviral “One-vector“ systems. (A) Unidirectional provirus transferring a “self-contained“ One-vector system. The tet-responsive promoter (TetO₇: tet-operator heptamer; P_R: regulatable minimal Promoter) drives expression of the gene of interest (gene “X“). Its inducibility is indicated by the black triangle. A constitutive promoter (P_C) drives expression of the tet-dependent transactivator (here exemplified by tTA) at a constant low level (black line). The unidirectional system utilizes the viral pA signal to terminate both transcripts and thereby generates overlapping transcripts. (B) The bidirectional system generates two distinct mRNAs, thus requires the insertion of an antisense orientated (−strand) pA-signal. (C) Unidirectional provirus transferring an “autoregulated“ One-vector system. A bicistronic unit couples the open reading frames of the gene of interest and the transactivator via an internal ribosomal entry site (IRES). The expression of both genes is driven by the inducible promoter (P_R).