Molecular determinants of the interactions between LXR/RXR heterodimers and TRAP220.
Dimerization-induced activation of LXR is a unique allosteric mechanism described only for LXR/RXR heterodimers. Previously, we demonstrated that RXR functions as an allosteric activator of LXR binding to ASC-2 coactivator rather than as a direct interaction partner. Here, we investigated the molecular basis of the interaction between LXR/RXR and TRAP220 fragment (TN1/2) harboring two NR boxes. We found that either LXR binding to NR box-2 or RXR binding to NR box-1 was sufficient for optimal LXR/RXR binding to TN1/2, indicating that both receptors contribute equally in this interaction. Notably, the AF2 deletion of either receptor completely abolished LXR/RXR-TN1/2 interaction, suggesting dual roles for both AF2 domains in direct interaction with target NR boxes as well as in allosteric activation of partner receptors. We also found specific residues within NR box-2 required for LXR binding using one- plus two-hybrid system and identified Pro(643) residue as a major determinant for NR specificity.
Son
You Lee
YL
Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju 500-757, Republic of Korea.
Lee
Young Chul
YC
D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D000071518:Liver X Receptors; D056913:Mediator Complex Subunit 1; D051379:Mice; D009154:Mutation; D057093:Orphan Nuclear Receptors; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D047488:Retinoid X Receptors / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D014157:Transcription Factors / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
D004268:DNA-Binding Proteins; D000071518:Liver X Receptors; C538855:MED1 protein, human; C538856:Med1 protein, mouse; D056913:Mediator Complex Subunit 1; D057093:Orphan Nuclear Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D047488:Retinoid X Receptors; D014157:Transcription Factors