Department of Biological Sciences, University of Texas at Dallas, Mail Stop RL11, 800 W. Campbell Road, Richardson, TX 75080, USA.
Diabetes Center, University of California San Francisco, San Francisco, CA 94143, USA.
Nucleic Acids Res. 2018 Jan 9;46(1):215-228. doi: 10.1093/nar/gkx1051.
The yeast Gis1 protein is a transcriptional regulator belonging to the JMJD2/KDM4 subfamily of demethylases that contain a JmjC domain, which are highly conserved from yeast to humans. They have important functions in histone methylation, cellular signaling and tumorigenesis. Besides serving as a cofactor in many proteins, heme is known to directly regulate the activities of proteins ranging from transcriptional regulators to potassium channels. Here, we report a novel mechanism governing heme regulation of Gis1 transcriptional and histone demethylase activities. We found that two Gis1 modules, the JmjN + JmjC domain and the zinc finger (ZnF), can bind to heme specifically in vitro. In vivo functional analysis showed that the ZnF, not the JmjN + JmjC domain, promotes heme activation of transcriptional activity. Likewise, measurements of the demethylase activity of purified Gis1 proteins showed that full-length Gis1 and the JmjN + JmjC domain both possess demethylase activity. However, heme potentiates the demethylase activity of full-length Gis1, but not that of the JmjN + JmjC domain, which can confer heme activation of transcriptional activity in an unrelated protein. These results demonstrate that Gis1 represents a novel class of multi-functional heme sensing and signaling proteins, and that heme binding to the ZnF stimulates Gis1 demethylase and transcriptional activities.
酵母 Gis1 蛋白是一种转录调节剂，属于 JMJD2/KDM4 去甲基酶亚家族，该亚家族含有 JmjC 结构域，从酵母到人高度保守。它们在组蛋白甲基化、细胞信号转导和肿瘤发生中具有重要功能。除了作为许多蛋白质的辅因子外，血红素已知可直接调节从转录调节剂到钾通道的蛋白质的活性。在这里，我们报告了一种新的机制，该机制控制血红素对 Gis1 转录和组蛋白去甲基酶活性的调节。我们发现，Gis1 的两个模块，JmjN + JmjC 结构域和锌指（ZnF），可以在体外特异性结合血红素。体内功能分析表明，ZnF 而不是 JmjN + JmjC 结构域促进血红素激活转录活性。同样，对纯化的 Gis1 蛋白的去甲基酶活性的测量表明，全长 Gis1 和 JmjN + JmjC 结构域都具有去甲基酶活性。然而，血红素增强全长 Gis1 的去甲基酶活性，但不能增强 JmjN + JmjC 结构域的去甲基酶活性，后者可以在不相关的蛋白质中赋予血红素激活转录活性。这些结果表明 Gis1 代表了一类新型多功能血红素感应和信号蛋白，血红素与 ZnF 的结合刺激 Gis1 的去甲基酶和转录活性。
