Tor complex 1 (TORC1), a master regulator of cell growth, is an evolutionarily conserved protein kinase within eukaryotic organisms. To control cell growth, TORC1 governs translational processes by phosphorylating its substrate proteins in response to cellular nutritional cues. Mammalian TORC1 (mTORC1) assumes the responsibility of phosphorylating the eukaryotic translation initiation factor 4E (eIF4E)-binding protein 1 (4E-BP1) to regulate its interaction with eIF4E. The budding yeast Saccharomyces cerevisiae possesses a pair of 4E-BP genes, CAF20 and EAP1. However, the extent to which the TORC1-4E-BP axis regulates translational initiation in yeast remains uncertain. In this study, we demonstrated the influence of TORC1 on the phosphorylation status of Caf20 in vivo, as well as the direct phosphorylation of Caf20 by TORC1 in vitro. Furthermore, we found the TORC1-dependent recruitment of Caf20 to the 80S ribosome. Consequently, our study proposes a plausible involvement of yeast's 4E-BP in the efficacy of translation initiation, an aspect under the control of TORC1.

中文翻译：

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酵母 Tor 复合物 1 磷酸化 eIF4E 结合蛋白 Caf20

Tor 复合物 1 (TORC1) 是细胞生长的主要调节因子，是真核生物体内进化上保守的蛋白激酶。为了控制细胞生长，TORC1 通过响应细胞营养信号磷酸化其底物蛋白来控制翻译过程。哺乳动物 TORC1 (mTORC1) 负责磷酸化真核翻译起始因子 4E (eIF4E) 结合蛋白 1 (4E-BP1)，以调节其与 eIF4E 的相互作用。芽殖酵母酿酒酵母拥有一对4E-BP基因，CAF20和EAP1。然而，TORC1-4E-BP 轴在酵母中调节翻译起始的程度仍不确定。在本研究中，我们证明了TORC1对体内Caf20磷酸化状态的影响，以及体外TORC1对Caf20的直接磷酸化状态的影响。此外，我们发现 Caf20 依赖于 TORC1 招募到 80S 核糖体。因此，我们的研究提出酵母的 4E-BP 可能参与翻译起始的功效，这是 TORC1 控制下的一个方面。