Rapamycin-induced translational derepression of GCN4 mRNA involves a novel mechanism for activation of the eIF2α kinase GCN2

Hiroyuki Kubota, Tohru Obata, Kazuhisa Ota, Takuma Sasaki, Takashi Ito

研究成果: Contribution to journalArticle査読

83 被引用数 (Scopus)

抄録

When starved for amino acids, Saccharomyces cerevisiae accumulates uncharged tRNAs to activate its sole eukaryotic initiation factor (eIF) 2α kinase GCN2. Subsequent phosphorylation of eIF2α impedes general translation, but translationally derepresses the transcription factor GCN4, which induces expression of various biosynthetic genes to elicit general amino acid control response. By contrast, when supplied with enough nutrients, the yeast activates the target of rapamycin signaling pathway to stimulate translation initiation by facilitating the assembly of eIF4F. A cross-talk was suggested between the two pathways by rapamycin-induced translation of GCN4 mRNA. Here we show that rapamycin causes an increase in phosphorylated eIF2α to translationally derepress GCN4. This increment is not observed in the cells expressing mammalian non-GCN2 eIF2α kinases in place of GCN2. It is thus suggested that rapamycin does not inhibit dephosphorylation of eIF2α but rather activates the kinase GCN2. This activation seems to require an interaction between the kinase and uncharged tRNAs, because rapamycin, similar to amino acid starvation, fails to induce eIF2α phosphorylation in the cells with GCN2 defective in tRNA binding. However, in contrast with amino acid starvation, rapamycin activates GCN2 without increasing the amount of uncharged tRNAs, but presumably by modifying the tRNA binding affinity of GCN2.

本文言語英語
ページ(範囲)20457-20460
ページ数4
ジャーナルJournal of Biological Chemistry
278
23
DOI
出版ステータス出版済み - 6 6 2003
外部発表はい

All Science Journal Classification (ASJC) codes

  • 生化学
  • 分子生物学
  • 細胞生物学

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