Figure 2.

Retroviral vector potential in regulated expression systems. (A) Scheme for target plasmids used. psps-Luc plasmid, in which a puromycin gene is located between two directed six sites under the control of an EF-1α promoter (upper). A luciferase gene is inserted downstream, followed by a hygromycin resistance gene. β Recombinase expression causes deletion of the puromycin gene including its stop codon and one six site, allowing luciferase reporter gene expression. Positive control plasmid (pLuc) with direct luciferase expression, under the same promoter (lower). Arrows indicate transcription units and arrowheads indicate specific primers used to detect recombination. (B) NIH-3T3 cells were electroporated with psps-Luc and pLuc, and hygromycin-resistant cells were selected. psps-Luc NIH-3T3-resistant cells were transduced with β-EGFP or β-ires-EGFP retroviral vectors; luciferase expression was measured after 48 h. The negative sample (neg) involves transduction of psps-Luc NIH-3T3-resistant cells with a control vector.