Figure 1.

Retrovirus-based vectors. (A) Representation of a retrovirus-based vector, and (B) a SIN lentiviral-based vector. The long terminal repeat (LTR) is divided into three regions (U3, R and U5). The packaging of the viral RNA takes place via interaction between the packaging signal ψ and the viral proteins. The bonding of Rev to the rev response element (RRE) enables the transport of un-spliced or once-spliced RNA from the nucleus to the cytoplasm. (C) A helper plasmid with viral protein gag-pro-pol under the expression of the cauliflower mosaic virus (CMV) promoter. (D) A helper plasmid for the env protein.