Fig. 1

Control of transgene expression from SeVdp vectors using the SrC switch. A Outline of the SrC switch system. Stabilizing DD-Csy4 with Shield1 decreases EGFP expression. B Structure of SeVdp vectors. NP, P/C/V, and L indicate SeV NP, P/C/V, and L genes, respectively. The P/C/V gene contains multiple open reading frames encoding P, C, and V proteins. NeoR: aminoglycoside 3′-phosphotransferase, KR: Keima-Red, DD: destabilizing domain, HA: HA-tag, Csy4RS: Csy4 recognition sequence. C DD-Csy4 protein expression upon Shield1 addition. SeV(HACsy4/RS-EGFP)-infected NIH3T3 cells were cultured with the indicated concentration of Shield1 for 3 days. Whole cell lysates extracted from the cells were subjected to Western blotting using anti-HA and anti-α-TUBULIN antibodies. Data are represented as the means ± SEM of three independent experiments. *p < 0.05. D Images of EGFP expression controlled by Shield1-responsive Csy4. NIH3T3 cells were infected with SeV(HACsy4/RS-EGFP) or SeV(Csy4/EGFP). After G418 selection, the cells were cultured with the indicated concentration of Shield1 for 5 days. EGFP and KR images were overlaid to produce merged images. Scale bars, 100 μm. E Fluorescent protein expression determined via flow cytometry. SeV(Csy4/RS-EGFP)-infected NIH3T3 cells were cultured with the indicated concentration of Shield1. EGFP and KR expression levels were determined using flow cytometry 3 or 5 days after Shield1 addition. Data are represented as the means ± SD of three independent experiments