IRES-mediated translation during cellular stress

细胞有两种不同的方式产生蛋白质，它们是帽依赖性翻译和内部核糖体进入位点（IRES）介导的翻译。大多数细胞蛋白质通过帽依赖性翻译产生，而大约5%的细胞mRNA和某些病毒mRNA通过IRES介导的翻译产生。我们仍然没有一个明确的答案，为什么哺乳动物细胞有两个不同的翻译系统。已知IRES介导的翻译在细胞应激和病毒感染下当帽依赖性翻译严重受损时通常是活跃的或维持的。因此，它被认为是一个故障安全的策略，其中IRES介导的翻译维持细胞内稳态作为备份的帽依赖性翻译在压力条件下。对于病毒，由IRES元件驱动的翻译机制可能是其复制的巨大优势，因为在细胞死亡期间可以实现病毒蛋白的有效合成。本实验室的长期研究目标是研究细胞在不同的细胞环境中如何调节这两种翻译机制。在当前NSERC资助期间（2006-2011年），我们发现氨基酸饥饿增加了口蹄疫病毒（FMDV）IRES元件启动的翻译效率。在拟议的研究中，我们将探讨蛋白质合成的细胞机制，如何通过口蹄疫病毒增加氨基酸饥饿。这项研究将在翻译控制、病毒学和细胞生理学领域产生重大影响。为了了解蛋白质合成是如何调节的，我们必须继续研究IRES介导的翻译的机制，并培养下一代研究人员。

Cells have two distinct ways to generate proteins which are cap-dependent translation and internal ribosomal entry site (IRES) mediated translation. The majority of cellular proteins are generated via cap-dependent translation while approximately 5% of cellular mRNA and certain viral mRNA are translated by IRES-mediated translation. We still do not have a clear answer as to why mammalian cells have two distinct translation systems. It is known that IRES-mediated translation is often active or maintained when cap-dependent translation is severely impaired under cellular stress and virus infection. Therefore, it is assumed that it is a fail-safe strategy in which IRES-mediated translation maintains cellular homeostasis as a backup of cap-dependent translation under stress conditions. For viruses, the translational machinery driven by IRES elements may be a great advantage for their replication since efficient synthesis of viral proteins can be achieved during cell death. The long-term research goal of our laboratory is to study how cells regulate the two translational machineries in different cellular environment. During the current NSERC funding period (2006-2011), we found that amino acid starvation increase translation efficiency initiated by foot-and-mouth disease virus (FMDV) IRES element. In the proposed study, we will investigate cellular mechanisms of how protein synthesis by FMDV is increased during amino acid starvation. The proposed study will have a significant impact in the field of translational control, virology and cell physiology. In order to understand how protein synthesis is regulated, it is essential that we continue to investigate the mechanisms that underlie IRES-mediated translation and to train the next generation of researchers.