Many of the nuclear hormone receptors have similar DNA binding sites. The VgEcR-RXR binds the sequence AGTGCATTGTTCTC in the synthetic response element (the binding sites for RXR and the GR DNA binding domains are underlined), the GR binding sequence is TGT(T/C)CT(G/T/C) (Beato et al. 1989; Nordeen et al. 1990), and, for comparison, the endogenous ecdysone receptor binds the sequence (A/G)G(G/T)T(C/T)A (Vogtli et al. 1998; Panguluri et al. 2007). It is also worth noting that RXR and HNF-4α can bind with similar affinity to direct repeats of (A/G)G(G/T)TCA with one base spacing (Nakshatri & Chambon 1994; Nakshatri & Bhat-Nakshatri 1998). Due to the similarities in the response elements, it seemed prudent to evaluate cellular responses to both VgEcR and GR as well as to evaluate RXR DNA-binding sequences.
