Heterodimerization of ecdysone receptor and ultraspiracle on symmetric and asymmetric response elements

Abstract

Heterodimerization of nuclear receptors is facilitated by the interaction of two dimerization interfaces: one spanning the DNA-binding (C domain) region and the adjacent hinge (D domain) region, and the other in the ligand-binding (E domain) region. Ultraspiracle (USP) heterodimerizes with ecdysone receptor (EcR) and this complex participates in ecdysone signal transduction. The natural ecdysone response elements (EcREs) discovered so far are asymmetric elements composed of either imperfect palindromes or direct repeats. However, gel mobility shift assays have shown that both symmetric (perfect palindromes) and asymmetric (imperfect palindromes and direct repeats) elements can bind to the EcR/USP complex. Therefore, we analyzed EcR/USP domains involved in heterodimerization on different types of response elements (RE). Gel shift assays using full-length and truncated EcR and USP proteins showed that heterodimerization of these two proteins in the presence of asymmetric RE (DR4 and the natural EcRE hsp27) requires both dimerization interfaces present in CD and E domains of both proteins. In contrast, the dimerization interface present in the E domain of either EcR or USP was not essential for heterodimerization on symmetric RE such as PAL1 or IR1. We conclude that the use of heterodimerization interfaces present in CD and E domains of EcR/USP depends on the nature of response elements they bind to.

Molecular determinants of caste differentiation in the highly eusocial honeybee Apis mellifera

“…Functional ecdysone response elements have been identified and it is now well established that the EcR-USP complex binds to direct or inverted (palindromic) repeats (rGkTCAATGaMCy) [78,55,79]. Another binding site pattern involving USP (CF1-USP) was already identified in D. melanogaster s15 chorion gene (GGGGTCAcs) [54].…”

Steroid signaling promotes stem cell maintenance in the Drosophila testis

“…20E acts by binding to a heterodimeric nuclear hormone receptor complex composed of Ecdysone receptor ( EcR ) and ultraspiracle ( usp ), which are mammalian orthologues of franesoid X receptor/liver X receptor and retinoid X receptor , respectively (Hayward et al, 1999; King-Jones and Thummel, 2005). This complex binds to specific promoter sequences, called Ecdysone Response Elements (EcREs), and can activate or repress the expression of hundreds of target genes which vary in response to the presence or absence of cell-type-specific co-activators (Carbonell et al, 2013; Francis et al, 2010; Jang et al, 2009; Perera et al, 2005; Tsai et al, 1999) (Fig. 1A).…”

The palindromic DNA-bound USP/EcR nuclear receptor adopts an asymmetric organization with allosteric domain positioning

“…The ecdysone response elements (EcREs) found in the promoter region of target genes generally consist of imperfect inverted repeats of two degenerated AG(G/T)TCA half-sites spaced by a single base pair (IR1) [1][2][3][4][5][6] . The usage of palindromic sequences distinguishes the invertebrate USP (ultraspiracle protein)/EcR receptor from its vertebrate RXR-(retinoid X receptor) heterodimeric counterparts, whose DNAbinding sites are composed primarily of inherently asymmetric, polar half-sites arranged as direct repeats (DRs) 7 .…”