Lentiviral vector design.

The modified U7 snRNA genes were inserted between the central polypurine track of HIV-1 (cPPT) and the downstream long terminal repeat (LTR) of the pTK134 plasmid (“Materials and methods”) in forward (pTKU7.324) or reverse (pTKU7.324r, pTKU7.623r) orientations. Transcription of the full-length vector RNA was driven by human cytomegalovirus (CMV) promoter. The vector also contains a packaging signal (ψ), the Rev response element (RRE), a sequence containing the woodchuck hepatitis virus posttranscriptional regulatory element (PRE), and a self-inactivating (SIN) deletion in the U3 region of the downstream LTR.