FIGURE 4.

Structure of the HIV-1 based vectors (lentiviral vectors) and the packaging cassettes. The third generation of the packaging cassette is shown. Upper panel (A) The wild type HIV-1 genome is shown. The genome contains four accessory proteins, Vpu, Vpr, Vif, and Nef and the regulatory proteins, tat and rev. RRE stands for rev response element. The 3^rd generation of the packaging vector cassette is shown. (lower panel) (B) Expression of lentiviral vector is driven from the CMV promoter; PolyA signal (pA) is shown. The 3rd generation excluded all four accessory proteins, Vpu, Vpr, Vif, and Nef, but included regulatory proteins, tat and rev. The vector packaging cassette contains RRE and pA signals. CMV, cytomegalovirus; RRE, Rev response element. Here, the transfer cassette depicted as RNA; 5′LTR and 3′LTR are listed. (C) Schematic image of viral DNA following the completion of RT process. U3′ region bears the promoter which drives an expression of the transcript. Self-inactivated vectors harbor deletion in U3 region, such that the full transcript expression is not supported. The internal promoter, painted in lilac color drives an expression of a transgene-of-interest (painted in green).