这篇文章于2017年11月22日在线发表于Plant Physiology，原题目为：

Polysomes, stress granules and processing bodies: a dynamic triumvirate controlling cytoplasmic mRNA fate and function

细胞质mRNA经历活性翻译形式的多聚核糖体，在受损或翻译抑制前会保持翻译活性状态（A）。抑制可以由多种原因引起（比如，改变特定翻译因子或RNA结合蛋白的丰度或磷酸化，以及核糖体停滞），从而限制翻译起始或核糖体转移，促进转变成翻译抑制的mRNP，这些mRNA可以被RNA 结合蛋白（例如，UBP1，G3BP和RBP45/47）封存，或是通过不同的途径降解（B）。通常通过细胞应激触发mRNA的封存，经伴侣分子（例如热应激恢复期间的HSP101）促进，进入翻译过程。一些从SGs释放的mRNA可能会在逆境胁迫后被降解（D）。在一般的mRNA降解中，通过不同类别的脱酰基酶（Nocturnin，Poly（A）-特异性核糖核酸酶（PARN）和CCR-NOT复合物）去除3'保护性多聚腺苷酸尾部，然后通过多聚体SKI-外泌体复合体和/或RRP44B/SOV核酸外切酶在3'至5’的方向降解。去腺苷酸化之后，也可以从5'至3'方向发生mRNA降解。通过这种模式降解的mRNA可以定位在胞质溶胶和/或PBs中，这里多蛋白质mRNA脱帽复合物去除保护性5'-帽子，随后5'-3' XRN4核糖核酸外切酶催化核苷酸水解（E）。除了脱腺苷依赖性的降解途径外，翻译抑制的mRNA可以在5'至3'方向上直接降解，而与通过XRN4介导的共翻译降解的延长核糖体相关联。这种降解模式绕过了脱腺苷酸化，但需要mRNA 脱帽。通过XRN4进行的mRNA的逐步5'-3'核酸外切，产生密码子-密码子 3-核苷酸标签，其被认为反映了大多数5'核糖体沿着转录本的运动（F）。缩写：AUG，翻译起始密码子; STOP，终止密码子

Figure 2. Overview of cytoplasmic mRNA translation, storage and decay in plants.

Cytoplasmic mRNAs undergoing active translation form polysomes and remain in a translationally active state until damaged or translationally repressed (A). Repression can result from multiple causes (i.e., altered abundance or phosphorylation of specific translation factors or RNA binding proteins and ribosome stalling) that limits translational initiation or ribosome translocation, promoting transition into a translationally repressed mRNP, where the mRNA is either sequestered by RNA-binding proteins (e.g., UBP1, G3BP, and RBP45/47) or degraded via different pathways (B). mRNA sequestration is typically triggered by cellular stress, serving as a enter translation via a process facilitated by a chaperone (e.g. HSP101 during heat stress recovery). Some mRNAs released from SGs may be targeted for degradation after stress (D). In general mRNA decay, the 3’ protective poly(A) tail is removed by different classes of deadenylases (Nocturnin, Poly(A)-specific ribonuclease (PARN) and CCR-NOT complex), then degradation proceeds in the 3’ to 5’ direction by the multimeric SKI-exosome complex and/or the RRP44B/SOV exonuclease. After deadenylation, mRNA degradation can also occur from the 5’ to 3’ direction. mRNAs degraded via this mode could be localized in the cytosol and/or PBs where the multi-protein mRNA decapping complex removes the protective 5’-cap, and subsequently the 5’-3’ XRN4 exoribonuclease catalyzes nucleotide hydrolysis (E). In addition to the deadenylation dependent decay pathway, translationally repressed mRNAs can be degraded directly in the 5’ to 3’ direction while in association with elongating ribosomes via XRN4-mediated co-translational decay. This mode of degradation bypasses deadenylation but requires mRNA decapping. The progressive 5’-3’ exonucleolytic destruction of the mRNA by XRN4 yields a codon-by-codon 3-nucleotide signature that is thought to reflect the movement of the most 5’ ribosome along the transcript (F). Abbreviations: AUG, translation initiation codon; STOP, termination codon.

每日一词

sequestration

英[ˌsi:kwə'streɪʃn]

美[ˌsikwɪˈstreʃən, ˌsɛkwɪ-]

n. 扣押，没收;

[例句]It also revealed which farming methods are best for carbon sequestration.

研究还显示了哪一种农业方式对于碳汇最有利