HPV E6 and E7 constructs used in the respective experiments.A, the E6 and E7 of HPV 16, 18, 31, 8, 38 used in the FACS–FRET assay were N-terminally fused with mTagBFP2 and EYFP, respectively. B, the untagged E6 and the N-terminally 3xHA-tagged E7 constructs of HPV 16 and HPV 31 were used in coimmunoprecipitation. C, the various constructs of HPV 16 and HPV 31 were used to produce purified recombinant proteins for analytical ultracentrifugation and fluorescence polarization. EYFP, enhanced YFP; FACS, fluorescence-activated cell sorting; HA, hemagglutinin; HPV, human papillomavirus.