Kubota H, Sakaki Y, Ito T
Division of Genome Biology, Cancer Research Institute, Kanazawa University, 13-1 Takaramachi, Kanazawa 920-0934, Tokyo, Japan.
J Biol Chem. 2000 Jul 7;275(27):20243-6. doi: 10.1074/jbc.C000262200.
In response to the starvation of a single amino acid, the budding yeast Saccharomyces cerevisiae activates numerous genes involved in various amino acid biosynthetic pathways, all of which are under the control of transcription factor GCN4. This general amino acid control response is based on de-repressed translation of GCN4 mRNA, which is induced by the activation of the eIF2alpha kinase, GCN2. Although it is known that in vivo activation of GCN2 requires GCN1, the mode of GCN1 action remains to be elucidated at the molecular level. Here, we show that GCN2 interacts with GCN1 via the GI domain, a novel protein-binding module that occurs at the N terminus; mutations to conserved residues of this domain abolish its binding to GCN1. Furthermore, the yeast cells with GCN2 defective in interaction with GCN1 fail to display general control response. A similar phenotype is observed in cells overexpressing the GI domain of GCN2 or its target region on GCN1. Thus, GI domain-mediated association of GCN2 to GCN1 is required for general amino acid control. This finding provides the first insight into the molecular mechanism for the activation of GCN2 by GCN1.
为应对单一氨基酸饥饿，出芽酵母酿酒酵母会激活众多参与各种氨基酸生物合成途径的基因，所有这些基因均受转录因子GCN4调控。这种一般氨基酸控制反应基于GCN4 mRNA的去阻遏翻译，该翻译由eIF2α激酶GCN2的激活所诱导。尽管已知GCN2在体内的激活需要GCN1，但其作用模式在分子水平上仍有待阐明。在此，我们表明GCN2通过GI结构域与GCN1相互作用，GI结构域是一种位于N端的新型蛋白质结合模块；该结构域保守残基的突变会消除其与GCN1的结合。此外，与GCN1相互作用存在缺陷的GCN2酵母细胞无法表现出一般控制反应。在过表达GCN2的GI结构域或其在GCN1上的靶区域的细胞中也观察到类似的表型。因此，一般氨基酸控制需要GI结构域介导的GCN2与GCN1的缔合。这一发现首次揭示了GCN1激活GCN2的分子机制。
