Kim Dae-Hwan, Kim Gwang Sik, Yun Chul Ho, Lee Young Chul
Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, 300 Yongbong-dong, Buk-gu, Gwangju 500-757, South Korea.
Mol Cell Biol. 2008 Feb;28(3):913-25. doi: 10.1128/MCB.01140-07. Epub 2007 Dec 10.
The yeast Gal11 protein, a component of the Mediator complex, is required for the transcriptional activation of many class II genes as a physiological target of various activator proteins in vivo. In this study, we identified the yeast (Saccharomyces cerevisiae) Mediator complex as a novel coactivator of the transcriptional activity of the glucocorticoid receptor (GR) tau 1 (tau1), the major transcriptional activation domain of the GR. GR tau1 directly interacted with the Mediator complex in vivo and in vitro in a Gal11 module-dependent manner, and the Gal11p subunit interacted directly with GR tau1. Specific amino acid residues within the glutamine-rich (Qr) domain of Gal11p (residues 116 to 277) were essential for its interaction with GR tau1 and GR tau1 transactivity in yeast, as demonstrated by mutational analysis of the Gal11 Qr domain, which is highly conserved among human steroid receptor coactivator (SRC) proteins. A Gal11p variant, mini-Gal11p, comprised of the Mediator association and Qr domains of Gal11p or chimeric mini-Gal11p containing the Qr domain of SRC-1 could potentiate the GR tau1 transactivity in a gal11Delta yeast strain. These results suggest that there is functional conservation between Qr domains of yeast Gal11p and mammalian SRC proteins as direct targets of activator proteins in yeast.
酵母Gal11蛋白是中介体复合物的一个组成部分，作为多种激活蛋白在体内的生理靶点，它是许多II类基因转录激活所必需的。在本研究中，我们鉴定出酵母（酿酒酵母）中介体复合物是糖皮质激素受体（GR）tau 1（tau1）转录活性的一种新型共激活因子，GR的主要转录激活结构域为tau1。GR tau1在体内和体外以Gal11模块依赖的方式直接与中介体复合物相互作用，并且Gal11p亚基直接与GR tau1相互作用。Gal11p富含谷氨酰胺（Qr）结构域（第116至277位氨基酸残基）内的特定氨基酸残基对于其在酵母中与GR tau1的相互作用以及GR tau1反式激活活性至关重要，Gal11 Qr结构域的突变分析证明了这一点，该结构域在人类类固醇受体共激活因子（SRC）蛋白中高度保守。由Gal11p的中介体结合结构域和Qr结构域组成的Gal11p变体mini-Gal11p，或含有SRC-1的Qr结构域的嵌合mini-Gal11p，可以增强gal11Δ酵母菌株中的GR tau1反式激活活性。这些结果表明，酵母Gal11p的Qr结构域与哺乳动物SRC蛋白之间存在功能保守性，作为酵母中激活蛋白的直接靶点。
