Diagrams of the plasmid and vectors expressing EGFP. Cartoons of the expression plasmid VR-EGFP, the MoMuLV-based vector encoding EGFP used in the packaging cell line PG-13, and the reporter gene vectors pHR′-CMV-EGFP and MLV-CMV-EGFP used in the transient packaging system. VR-EGFP contains a CMV promoter/enhancer (CMV prom/enh) and intron from CMV, the EGFP gene and bovine growth hormone polyadenylation signal (BGH term) in a plasmid-encoding kanamycin resistance (Kan). L-EGFP-SN is an MoMuLV-based vector containing the 5′LTR and 3′LTR from MoMuLV, the EGFP gene, an SV40 early promoter, and the bacterial neomycin phosphotransferase gene (NEO). pHR′-CMV-EGFP is a lentiviral vector containing HIV-1–derived elements, including the 5′LTR and 3′LTR, the splice donor (SD) and splice acceptor (SA), the packaging signal (Ψ), a portion of the gag encoding region (GA), a CMV prom/enh (CMV), and the EGFP gene. MLV-CMV-EGFP is another MoMuLV-based vector containing the 5′LTR and 3′LTR of MoMuLV, the bacterial neomycin phosphotransferase gene (NEO), the CMV prom/enh (CMV), and the EGFP gene.