Figure 1.

Schematic diagram of expression constructs. (a) The single cistronic expression constructs. (b) The double cistronic expression constructs. Bacterial (Tac) or phage (T7) promoters are indicated by arrows. Repressor binding sites are represented by open boxes. E. coli ribosome-binding sites are represented by open circles. In the first construct, RXR and RAR LBDs are fused at their N termini to GST and H6, respectively. In the second construct, both receptor LBDs are fused to H6. The order of transcription of RXR and RAR in the two constructs is reversed. The third and fourth constructs are similar to the first one except that the receptors are ECR/USP and ECR/RXR, respectively.