FIG. 1.

Transgene structure and DOX-dependent transgene expression. (A) TRE/HIV^Nef. Crossed thin bar, TRE promoter sequences; thick bar, HIV-1^Nef sequences in which all HIV-1 genes except nef are disrupted (X); dark bar, SV40 poly(A) sequences. (B) CD4C/rtTA and CD4C/rtTA2^S-M2. The human CD4 promoter (thin bar) was fused to the mouse enhancer (striped bar). Stripted arrow, rtTA or rtTA2^S-M2; dark bar, SV40 poly(A) sequences. (C) Northern blot analysis of HIV-1 RNA of thymus from mice treated for 1 week with different concentrations of DOX in drinking water. Total RNA (15 μg) extracted from thymuses was hybridized with ³²P-labeled HIV-1-specific probe. RNA from CD4C/HIV^Nef (F27367) mice was used as a positive control. To control sample loading, blots were washed and rehybridized with actin-specific probe. (D and E) Western blot analysis of Nef protein of thymuses and peripheral LN (D) and of peritoneal macrophages (E) of different transactivator founder lines treated with DOX (2 mg/ml) in drinking water for 1 week. Protein extracts (100 μg) from different organs were blotted with anti-Nef serum and antiactin antibody. Protein samples from CD4C/HIV^Nef (F27367) mice were used as positive controls. (F) Histogram plots of GFP expression detected by FACS analysis in thymic populations of representative mice treated with DOX (2 mg/ml) for 1 week and untreated controls. The percentages of the indicated gated GFP⁺ cells are indicated.