Eap1p, a novel eukaryotic translation initiation factor 4E-associated protein in Saccharomyces cerevisiae
Eap1p, a novel eukaryotic translation initiation factor 4E-associated protein in Saccharomyces cerevisiae
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DOI：
10.1128/mcb.20.13.4604-4613.2000
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发表时间：
2000-07-01
影响因子：
5.3
通讯作者：
Sonenberg, N
中科院分区：
文献类型：
--
作者：
Cosentino, GP;Schmelzle, T;Sonenberg, N
核糖体与真核细胞mRNA的结合是一个多步骤的过程，它由位于所有细胞(细胞器除外)mRNA5‘末端的帽子结构[m(7)G(5’)PPP(5‘)N，其中N是任何核苷酸]介导。异三聚体复合体，真核起始因子4F(EIF4F)，通过eIF4E亚基直接与帽子结构相互作用，并在mRNA上组装核糖体起始复合体。在哺乳动物细胞中，eIF4E的活性部分由三个相关的翻译抑制物(4E-Bps)调节，它们直接与eIF4E结合，阻止eIF4F的组装。在发芽酵母酿酒酵母中不存在4E-BPS的结构上的对应物。然而，已经描述了一种功能同源物(名为p20)，它通过类似于4e-bps的机制阻止帽子依赖的翻译。我们在这里报道了一种新的酵母eIF4E相关蛋白(Eap1p)的特征，它也可以通过与eIF4E结合来调节翻译。Eap1p在包含典型的eIF4E结合基序的区域与p20同源性有限。这个结构域或点突变的缺失会消除Eap1p与eIF4E的相互作用。Eap1p在体内与eIF4G(帽结合复合体的大亚基，eIF4F)和p20竞争结合eIF4E，并在体外抑制帽依赖的翻译。EAP1基因的靶向破坏导致了温度敏感的表型，也赋予了对雷帕霉素抑制生长的部分抗性。这些数据表明，Eap1p在细胞生长中发挥作用，并与酿酒酵母的TOR信号级联反应有关。
Ribosome binding to eukaryotic mRNA is a multistep process which is mediated by the cap structure [m(7)G(5')ppp(5')N, where N is any nucleotide] present at the 5' termini of all cellular (with the exception of organellar) mRNAs. The heterotrimeric complex, eukaryotic initiation factor 4F (eIF4F), interacts directly with the cap structure via the eIF4E subunit and functions to assemble a ribosomal initiation complex on the mRNA. In mammalian cells, eIF4E activity is regulated in part by three related translational repressors (4E-BPs), which bind to eIF4E directly and preclude the assembly of eIF4F. No structural counterpart to 4E-BPs exists in the budding yeast, Saccharomyces cerevisiae. However, a functional homolog (named p20) has been described which blocks cap-dependent translation by a mechanism analogous to that of 4E-BPs. We report here on the characterization of a novel yeast eIF4E-associated protein (Eap1p) which can also regulate translation through binding to eIF4E. Eap1p shares limited homology to p20 in a region which contains the canonical eIF4E-binding motif. Deletion of this domain or point mutation abolishes the interaction of Eap1p with eIF4E. Eap1p competes with eIF4G (the large subunit of the cap-binding complex, eIF4F) and p20 for binding to eIF4E in vivo and inhibits cap-dependent translation in vitro. Targeted disruption of the EAP1 gene results in a temperature-sensitive phenotype and also confers partial resistance to growth inhibition by rapamycin. These data indicate that Eap1p plays a role in cell growth and implicates this protein in the TOR signaling cascade of S. cerevisiae.