Wissink S, van Heerde E C, Schmitz M L, Kalkhoven E, van der Burg B, Baeuerle P A, van der Saag P T
Hubrecht Laboratory, Netherlands Institute for Developmental Biology, Utrecht, The Netherlands.
J Biol Chem. 1997 Aug 29;272(35):22278-84. doi: 10.1074/jbc.272.35.22278.
The RelA subunit of NF-kappaB and the glucocorticoid receptor mutually repress each others transcriptional activity, thus providing a mechanism for immunosuppression. Deletion analysis of the glucocorticoid receptor has shown that the DNA binding domain and the ligand binding domain are essential components for repression. Here, we show by deletions and point mutations that both the Rel homology domain and the transactivation domains of RelA are required for repression of the transcriptional activity of the glucocorticoid receptor in intact cells. However, only the Rel homology domain of RelA was found to associate with the glucocorticoid receptor in vitro. RelA mutants, not able to repress glucocorticoid receptor activity, but still able to dimerize, behaved as transdominant inhibitors of the repressive activity of wild type RelA. Furthermore, we show that the 13 S E1A protein is able to interfere with the transrepressive activity of RelA. We propose that negative cross-talk between the glucocorticoid receptor and RelA is due to direct interaction via the Rel homology domain of RelA and the DNA binding domain of the glucocorticoid receptor in combination with interference by the transactivation domains of RelA with the transcriptional activity of the glucocorticoid receptor.
核因子-κB的RelA亚基与糖皮质激素受体相互抑制彼此的转录活性，从而提供了一种免疫抑制机制。对糖皮质激素受体的缺失分析表明，DNA结合结构域和配体结合结构域是抑制作用的关键组成部分。在此，我们通过缺失和点突变表明，RelA的Rel同源结构域和反式激活结构域对于完整细胞中糖皮质激素受体转录活性的抑制都是必需的。然而，在体外仅发现RelA的Rel同源结构域与糖皮质激素受体相关联。不能抑制糖皮质激素受体活性但仍能二聚化的RelA突变体，表现为野生型RelA抑制活性的反式显性抑制剂。此外，我们表明13S E1A蛋白能够干扰RelA的反式抑制活性。我们提出，糖皮质激素受体与RelA之间的负性相互作用是由于RelA的Rel同源结构域与糖皮质激素受体的DNA结合结构域直接相互作用，同时RelA的反式激活结构域干扰了糖皮质激素受体的转录活性。
