Figure 1.

Interaction panel of LexAbHLH-PAS fusion proteins with full-length MOP3 and ARNT. (Upper) Schematic representation of the LexAbHLHPAS “bait” and the full-length “fish.” The bHLH and PAS domains are boxed. The “A” and “B” repeats of the PAS domains are indicated. The transactivation domain of the full-length “fish” is indicated. (Lower) LexA fusion protein plasmids containing the bHLH-PAS domains of HIF1α, HIF2α, MOP3, MOP4, AHR, ARNT, and CLOCK were coexpressed with plasmids harboring full-length MOP3 and ARNT (see Materials and Methods). LexAAHR interactions were assayed on plates containing 1 μM β-naphthoflavone (14). After incubation, an 5-bromo-4-chloro-3-indolyl β-d-galactoside overlay assay was performed. ++, A strong interaction, turning blue within 2 hr; +, a weaker interaction, turning blue between 8 hr and overnight; and −, a negative interaction after overnight incubation. The experiment was performed three times with identical results.