Figure 1.

Schematic of retroviral vector constructs used in this study. The two-color constructs (left boxes) are based on the HIV NL4-3 genome with the following modifications from left to right: mutation of the myristoylation signal in gag, truncation of gag, addition of a CHYSEL sequence and an eGFP gene in the gag reading frame, deletion of the frameshifting site, missense mutation of the rev start codon, insertion of a stop codon in the first exon of rev, introduction of a frameshift mutation in env, placement of an XmaI and an XbaI site flanking the RRE within env, and deletion of the beginning of nef with the substitution of a second fluorescent protein in this position. The single-color constructs (right boxes) are MSCV vectors modified with a rev gene flanked by two restriction enzyme sites as well as an in-frame IRES and a fluorescent protein gene. Two construct sets were used in this study. (a) Construct set A has an eGFP in the gag reading frame, mCherry in the nef reading frame, and TagBFP in the Rev vector. (b) Construct set B has an eGFP in the gag reading frame, TagBFP in the nef reading frame, and mCherry in the Rev vector. Myr = myristoylation site, CHYSEL = cis-acting hydrolase element, f.s. = frameshift site, LTR = long terminal repeat, GFP = green fluorescent protein, BFP = blue fluorescent protein, RFP = red fluorescent protein, MSCV = murine stem cell virus, IRES = internal ribosomal entry site, ψ = packaging signal.