Radioisotope Center, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
Biochem Biophys Res Commun. 2012 Feb 3;418(1):149-55. doi: 10.1016/j.bbrc.2011.12.150. Epub 2012 Jan 8.
The stress response, which can trigger various physiological phenomena, is important for living organisms. For instance, a number of stress-induced granules such as P-body and stress granule have been identified. These granules are formed in the cytoplasm under stress conditions and are associated with translational inhibition and mRNA decay. In the nucleus, there is a focus named nuclear stress body (nSB) that distinguishes these structures from cytoplasmic stress granules. Many splicing factors and long non-coding RNA species localize in nSBs as a result of stress. Indeed, tRNAs respond to several kinds of stress such as heat, oxidation or starvation. Although nuclear accumulation of tRNAs occurs in starved Saccharomyces cerevisiae, this phenomenon is not found in mammalian cells. We observed that initiator tRNA(Met) (Meti) is actively translocated into the nucleus of human cells under heat stress. During this study, we identified unique granules of Meti that overlapped with nSBs. Similarly, elongator tRNA(Met) was translocated into the nucleus and formed granules during heat stress. Formation of tRNA granules is closely related to the translocation ratio. Then, all tRNAs may form the specific granules.
应激反应可以触发各种生理现象，对生物体很重要。例如，已经鉴定出了许多应激诱导的颗粒，如 P 体和应激颗粒。这些颗粒在应激条件下在细胞质中形成，并与翻译抑制和 mRNA 衰变有关。在核内，有一个称为核应激体（nSB）的焦点，将这些结构与细胞质应激颗粒区分开来。许多剪接因子和长非编码 RNA 物种由于应激而定位于 nSBs 中。事实上，tRNA 对多种应激（如热、氧化或饥饿）有反应。尽管在饥饿的酿酒酵母中观察到 tRNA 的核积累，但在哺乳动物细胞中没有发现这种现象。我们观察到起始 tRNA（Met）（Meti）在热应激下被主动转运到人细胞的核内。在这项研究中，我们鉴定了与 nSBs 重叠的 Meti 独特颗粒。同样，延伸因子 tRNA（Met）在热应激时被转运到核内并形成颗粒。tRNA 颗粒的形成与转运比率密切相关。那么，所有的 tRNA 可能形成特定的颗粒。
