RXR agonist modulates TR: corepressor dissociation upon 9-cis retinoic acid treatment
Overview of Fattori J et al.
Authors | Fattori J  Campos JL  Doratioto TR  Assis LM  Vitorino MT  Polikarpov I  Xavier-Neto J  Figueira AC   |
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Affiliation | Centro Nacional de Pesquisa em Energia e Materiais (J.F.   J.L.O.C.   T.R.D.   L.M.A.   M.T.V.   J.X.-N.   A.C.M.F.)   Laboratório Nacional de Biociências   Campinas SP   13083-970   Brazil; and Instituto de Física de São Carlos (I.P.)   Universidade de São Paulo   São Carlos SP   13560-970   Brazil.   |
Journal | Mol Endocrinol |
Year | 2014 |
Abstract
Transcriptional regulation controlled by thyroid hormone receptor (TR) drives events such as development, differentiation, and metabolism. TRs may act either as homodimers or as heterodimers with retinoid X receptor (RXR). Thyroid hormone T3 preferentially binds TR-RXR heterodimers, which activate transcription through coactivator recruitment. However, it is unclear whether TR-RXR heterodimers may also be responsive to the canonical RXR agonist 9-cis retinoic acid (9C) in the context of physiological gene regulation. New structural studies suggest that 9C promotes the displacement of bound coactivators from the heterodimer, modifying TR-RXR activity. To shed light on the molecular mechanisms that control TR-RXR function, we used biophysical approaches to characterize coregulator recruitment to TR-TR or to TR-RXR in the presence of T3 and/or 9C as well as cell-based assays to establish the functional significance of biophysical findings. Using cell-based and fluorescence assays with mutant and wild-type TR, we show that 9C does indeed have a function in the TR-RXR heterodimer context, in which it induces the release of corepressors. Furthermore, we show that 9C does not promote detectable conformational changes in the structure of the TR-RXR heterodimer and does not affect coactivator recruitment. Finally, our data support the view that DNA binding domain and Hinge regions are important to set up NR-coactivator binding interfaces. In summary, we showed that the RXR agonist 9C can regulate TR function through its modulation of corepressor dissociation.