Kersten S, Gronemeyer H, Noy N
Cornell University, Division of Nutritional Sciences, Savage Hall, Ithaca, New York 14853-6301, USA.
J Biol Chem. 1997 May 9;272(19):12771-7. doi: 10.1074/jbc.272.19.12771.
The retinoid X receptor (RXR) regulates target gene transcription via its association with cognate DNA response elements either as a homodimer or as a heterodimer with a number of other nuclear receptors. We previously demonstrated that, in solution, RXR forms tetramers with a high affinity and that ligand binding leads to dissociation of receptor tetramers to smaller species. Here it is shown that RXR tetramers form stable complexes with direct repeats (DR-1 or DR-5) or palindromic (TREpal) response elements. Binding of RXR tetramers to cognate DNA occurs with a significantly higher affinity as compared with dimers. Ligand binding by DNA-bound RXR tetramers results in their dissociation to DNA-bound dimers, a process that is completely reversed upon removal of the ligand. Formation of stable tetramer-DNA complexes requires binding of two oligonucleotides/tetramer. It is proposed that ligand-dependent modulation of the oligomeric state of RXR is a regulatory feature of this nuclear receptor.
维甲酸X受体（RXR）通过与同源DNA反应元件结合来调节靶基因转录，其结合形式可以是同二聚体，也可以是与许多其他核受体形成的异二聚体。我们之前证明，在溶液中，RXR会以高亲和力形成四聚体，并且配体结合会导致受体四聚体解离为较小的物种。本文表明，RXR四聚体与直接重复序列（DR-1或DR-5）或回文（TREpal）反应元件形成稳定的复合物。与二聚体相比，RXR四聚体与同源DNA的结合亲和力显著更高。DNA结合的RXR四聚体与配体结合会导致它们解离为DNA结合的二聚体，去除配体后，这一过程会完全逆转。稳定的四聚体-DNA复合物的形成需要两个寡核苷酸/四聚体的结合。有人提出，RXR寡聚状态的配体依赖性调节是这种核受体的一个调节特征。
