Figure 1.

In vitro evolution of the dox-dependent HIV-rtTA virus. (A) Schematic of the original HIV-rtTA virus genome that was used as the starting point of the evolution. The inactivated Tat/TAR elements (black) and the introduced rtTA/8 tetO elements of the Tet system (gray) are indicated. (B) Modified tetO configurations obtained by evolution of the original 8 tetO LTR in the SupT1 T cell line. (C) Representative example of an evolution experiment. The LTR promoter region was PCR-amplified at different times and resolved on gel. Asterisks indicate bands that were identified by sequencing. (D) Spacing of tetO elements in the E. coli Tn10 operon, the original HIV-rtTA virus, and the evolved 2Δ tetO elements.