Department of Systems Biology, Yonsei University, Seoul 120-749, Korea.
Department of Systems Biology, Yonsei University, Seoul 120-749, Korea
Plant Cell. 2017 Nov;29(11):2895-2920. doi: 10.1105/tpc.17.00563. Epub 2017 Oct 30.
Dynamic control of protein translation in response to the environment is essential for the survival of plant cells. Target of rapamycin (TOR) coordinates protein synthesis with cellular energy/nutrient availability through transcriptional modulation and phosphorylation of the translation machinery. However, mechanisms of TOR-mediated translation control are poorly understood in plants. Here, we report that (MA3 DOMAIN-CONTAINING TRANSLATION REGULATORY FACTOR) family genes encode translation regulatory factors under TOR control, and their functions are particularly important in energy-deficient conditions. Four family genes (-) are transcriptionally induced by dark and starvation (DS). Silencing of multiple increases susceptibility to DS and treatment with a TOR inhibitor, while overexpression decreases susceptibility. MRF proteins interact with eIF4A and cofractionate with ribosomes. silencing decreases translation activity, while overexpression increases it, accompanied by altered ribosome patterns, particularly in DS. Furthermore, MRF deficiency in DS causes altered distribution of mRNAs in sucrose gradient fractions and accelerates rRNA degradation. MRF1 is phosphorylated in vivo and phosphorylated by S6 kinases in vitro. expression and MRF1 ribosome association and phosphorylation are modulated by cellular energy status and TOR activity. We discuss possible mechanisms of the function of MRF family proteins under normal and energy-deficient conditions and their functional link with the TOR pathway.
动态控制蛋白质翻译以响应环境对于植物细胞的生存至关重要。雷帕霉素靶蛋白(TOR)通过转录调节和翻译机制的磷酸化来协调蛋白质合成与细胞能量/营养可用性。然而,植物中 TOR 介导的翻译控制机制知之甚少。在这里,我们报告说 (MA3 结构域包含的翻译调控因子)家族基因编码 TOR 控制下的翻译调控因子,它们的功能在能量不足的条件下尤为重要。四个 家族基因(-)被黑暗和饥饿(DS)转录诱导。多个 的沉默增加了对 DS 和 TOR 抑制剂处理的敏感性,而 的过表达则降低了敏感性。MRF 蛋白与 eIF4A 相互作用,并与核糖体共分馏。沉默减少翻译活性,而过表达则增加翻译活性,同时伴随着核糖体模式的改变,尤其是在 DS 中。此外,DS 中 MRF 的缺失导致 mRNA 在蔗糖梯度部分中的分布改变,并加速 rRNA 的降解。MRF1 在体内被磷酸化,并且在体外被 S6 激酶磷酸化。表达和 MRF1 核糖体的结合和磷酸化受细胞能量状态和 TOR 活性的调节。我们讨论了 MRF 家族蛋白在正常和能量不足条件下的功能的可能机制及其与 TOR 途径的功能联系。