AhR is required for rVpr-induced L1-RTP. A. AhR siRNA down-regulated expression of endogenous protein. Lane 1, untreated (U); lane 2, mock transfection without siRNA (N); lane 3, control siRNA (C); lane 4, AhR siRNA. B. AhR siRNA attenuated rVpr-induced L1-RTP. C. ARNT1 siRNA down-regulated expression of endogenous ARNT1 protein. Lane 1, untreated (U); lane 2, mock transfection without siRNA (N); lane 3, control siRNA (C); lane 4, ARNT1 siRNA. D. ARNT1 is dispensable for L1-RTP induction by rVpr. E. No induction of L1-RTP by the LA mutant. Left panel. Result of L1-RTP after transfection of plasmid DNA encoding wild-type Vpr (WT) or the LA mutant. Lanes 1 and 4, vector control (Vec); lanes 2 and 5, WT Vpr; lanes 3 and 6, LA mutant (LAM). Right panel. Expression levels of WT Vpr and the LA mutant were comparable. F. Association with AhR was impaired in the LA mutant. HEK293T cells were transfected with constructs expressing FLAG-EGFP, FLAG-Vpr-Wt or FLAG-Vpr-LAM. Cell extracts were subjected to IP with α-FLAG followed by WB using α-AhR (upper panel) or α-FLAG (lower panel). Lanes 1, 4 and 7, vector control (FLAG-EGFP); lanes 2, 5 and 8, FLAG-Vpr-Wt; lanes 3, 6 and 9, FLAG-Vpr-LAM. α-SARS mAb was used for control-IP.