Dever T E, Feng L, Wek R C, Cigan A M, Donahue T F, Hinnebusch A G
Section on Molecular Genetics of Lower Eukaryotes, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892.
Cell. 1992 Feb 7;68(3):585-96. doi: 10.1016/0092-8674(92)90193-g.
We show that phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF-2) by the protein kinase GCN2 mediates translational control of the yeast transcriptional activator GCN4. In vitro, GCN2 specifically phosphorylates the alpha subunit of rabbit or yeast eIF-2. In vivo, phosphorylation of eIF-2 alpha increases in response to amino acid starvation, which is dependent on GCN2. Substitution of Ser-51 with alanine eliminates phosphorylation of eIF-2 alpha by GCN2 in vivo and in vitro and abolishes increased expression of GCN4 and amino acid biosynthetic genes under its control in amino acid-starved cells. The Asp-51 substitution mimics the phosphorylated state and derepresses GCN4 in the absence of GCN2. Thus, an established mechanism for regulating total protein synthesis in mammalian cells mediates gene-specific translational control in yeast.
我们发现，蛋白激酶GCN2对真核生物翻译起始因子2（eIF-2）的α亚基进行磷酸化作用，介导了酵母转录激活因子GCN4的翻译调控。在体外，GCN2可特异性地使兔源或酵母源eIF-2的α亚基发生磷酸化。在体内，eIF-2α的磷酸化会随着氨基酸饥饿而增加，且这一过程依赖于GCN2。将丝氨酸51突变为丙氨酸会消除GCN2在体内和体外对eIF-2α的磷酸化作用，并在氨基酸饥饿的细胞中，消除受其调控的GCN4及氨基酸生物合成基因的表达增加现象。天冬氨酸51的替代突变模拟了磷酸化状态，并在缺乏GCN2的情况下解除了对GCN4的抑制。因此，一种在哺乳动物细胞中已明确的调控总蛋白合成的机制，在酵母中介导了基因特异性的翻译调控。
