GCN1, a translational activator of GCN4 in Saccharomyces cerevisiae, is required for phosphorylation of eukaryotic translation initiation factor 2 by protein kinase GCN2-猫眼课题宝

GCN1 是酿酒酵母中 GCN4 的翻译激活剂，是蛋白激酶 GCN2 磷酸化真核翻译起始因子 2 所必需的

DOI：

10.1128/mcb.13.6.3541-3556.1993

发表时间：

1993

期刊：

Molecular and Cellular Biology

影响因子：

5.3

通讯作者：

中科院分区：

生物学2区

文献类型：

作者：

Thew J. Marton;Deborah Crouch;A. Hinnebusch

蛋白激酶GCN 2磷酸化真核翻译起始因子2（eIF-2 α）的α亚基介导氨基酸饥饿酵母细胞中转录激活因子GCN 4的翻译增加。我们表明，这一关键的磷酸化事件和随之而来的翻译诱导GCN 4依赖于一个以前未知的基因，GCN 1的产品。当在酵母细胞中表达哺乳动物eIF-2 α激酶代替GCN 2时，GCN 1的失活并不影响eIF-2 α磷酸化水平，这与GCN 1参与eIF-2 α的去磷酸化有关。此外，虽然GCN 2在体内磷酸化eIF-2 α需要GCN 1，但gCN 1 δ菌株的细胞提取物含有野生型水平的GCN 2 eIF-2 α-激酶活性。在这些结果的基础上，我们提出，GCN 1是不需要的GCN 2激酶活性本身，但需要在体内激活GCN 2响应饥饿信号，不带电的tRNA。GCN 1编码一个297 kDa的蛋白质，其中88 kDa的区域在序列上与几种真菌中鉴定的翻译延伸因子3高度相似。这种序列相似性提高了GCN 1与核糖体或tRNA分子相互作用的可能性，并与GCN 2一起在翻译延伸过程中监测不带电荷的tRNA水平。

Phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF-2 alpha) by the protein kinase GCN2 mediates increased translation of the transcriptional activator GCN4 in amino acid-starved yeast cells. We show that this key phosphorylation event and the attendant translational induction of GCN4 are dependent on the product of a previously uncharacterized gene, GCN1. Inactivation of GCN1 did not affect the level of eIF-2 alpha phosphorylation when mammalian eIF-2 alpha kinases were expressed in yeast cells in place of GCN2, arguing against an involvement of GCN1 in dephosphorylation of eIF-2 alpha. In addition, while GCN1 is required in vivo for phosphorylation of eIF-2 alpha by GCN2, cell extracts from gcn1 delta strains contained wild-type levels of GCN2 eIF-2 alpha-kinase activity. On the basis of these results, we propose that GCN1 is not needed for GCN2 kinase activity per se but is required for in vivo activation of GCN2 in response to the starvation signal, uncharged tRNA. GCN1 encodes a protein of 297 kDa with an 88-kDa region that is highly similar in sequence to translation elongation factor 3 identified in several fungal species. This sequence similarity raises the possibility that GCN1 interacts with ribosomes or tRNA molecules and functions in conjunction with GCN2 in monitoring uncharged tRNA levels during the process of translation elongation.