A mechanoresponsive signalling pathway disassembles processing bodies

机械反应信号通路分解处理体处理体(PBS)是细胞质核糖核蛋白颗粒，从根本上调节基因的表达。PBS降解或隔离mRNA，以控制细胞转录产物翻译成蛋白质。PB是动态的；它们在各种刺激下形成和分解。当它们被分解后，PB定位的mRNAs解除了抑制，使PBS成为一个重要的调控开关。然而，控制‘PB开关’的确切信号并没有得到很好的定义。在我们的NSERC资助的研究计划中，我们发现了一条新的机械响应信号通路，可以引起PB的分解，从而为理解PB对基因表达的控制提供了新的知识。细胞受到持续不断的机械刺激，这会影响被称为机械转导的过程中的行为。外力转化为细胞内生化信号需要形成较厚的肌动蛋白束，称为肌动蛋白应力纤维(SFS)。它们激活机械反应转录调节蛋白YAP，将其移位到细胞核，在那里它调节基因转录。我们先前已经证明，病毒KapB蛋白诱导肌动蛋白SFS的形成和PBS的分解。使用RNA沉默，我们不能从遗传上分离这两种表型。相反，我们证明了SFS的KapB诱导是PB分解所必需的。此外，沉默YAP消除了KapB介导的PB拆解。YAP的生物化学活性版本或细胞暴露在机械力下激活YAP也会导致PB分解。这些数据表明，YAP是KapB介导的PB分解所必需的，足以分解PB，并揭示了机械反应性转录激活因子与PBS的调控之间的联系。在我们NSERC资助的研究计划的继续中，我们将进一步定义机械力、YAP激活和PB拆卸之间的信号。我们提出了三个具体的目标：1)表征导致PB分解的机械信号；2)确定KapB从细胞内激发的机械信号如何影响YAP的激活；3)阐明YAP介导的PB分解的影响和意义：我们的研究促进了对YAP机械转导作用的基本理解。我们证明了PBS受机械信号事件的调节，这些信号事件改变了肌动蛋白SFS，并需要机械反应转录因子YAP。KapB在细胞内激活一条途径，通过细胞质PBS将细胞形状与转录后基因调控联系起来。这一点很重要，因为许多其他刺激诱导肌动蛋白SFS、肌动蛋白收缩、细胞形状变化和活性YAP，我们的工作预测这些刺激也会导致PB解体来调节细胞基因的表达。

A mechanoresponsive signalling pathway disassembles processing bodies Processing bodies (PBs) are cytoplasmic ribonucleoprotein granules that fundamentally regulate gene expression. PBs degrade or sequester mRNA to control what cellular transcripts are translated into protein. PBs are dynamic; they form and disassemble in response to various stimuli. Upon their disassembly, PB-localized mRNAs are relieved of repression, making PBs an important regulatory switch. However, the precise signals that control the `PB switch' are not well defined. With our NSERC-funded research program, we identified a novel mechanoresponsive signalling pathway that elicits PB disassembly, thereby contributing new knowledge to the fundamental understanding of PB control of gene expression. Cells are subject to constant mechanical stimulation that influences behaviour in a process called mechanotransduction. The conversion of external forces into intracellular biochemical signals requires formation thick actin bundles called actin stress fibres (SFs). These activate the mechanoresponsive transcriptional regulator, Yes-associated protein (YAP) to translocate to the nucleus where it regulates gene transcription. We previously showed that the viral KapB protein induced the formation of actin SFs and the disassembly of PBs. Using RNA silencing, we were not able to genetically separate these two phenotypes. Instead, we demonstrated that KapB induction of SFs was required for PB disassembly. Moreover, silencing YAP eliminated KapB-mediated PB disassembly. A biochemically active version of YAP or the exposure of cells to mechanical forces known to activate YAP also caused PB disassembly. These data indicated that YAP was necessary for KapB-mediated PB disassembly, sufficient for PB disassembly and revealed a connection between a mechanoresponsive transcription activator and the regulation of PBs. In a continuation of our NSERC-funded research program, we will further define the signals between mechanical forces, YAP activation and PB disassembly. We propose three specific aims: 1) Characterize mechanical signals that lead to PB disassembly, 2) Identify how mechanical signals elicited from within the cell by KapB influence YAP activation, 3) Elucidate the mechanism of YAP-mediated PB disassembly Impact and Significance: Our studies advance the fundamental understanding of the role of YAP mechanotransduction. We demonstrated that PBs are regulated by mechanical signalling events that alter actin SFs and require the mechanoresponsive transcription factor, YAP. KapB activates, from within the cell, a pathway that links cell shape to post-transcriptional gene regulation via cytoplasmic PBs. This is important because many other stimuli induce actin SFs, actin contractility, changes to cell shape, and active YAP and our work predicts that these stimuli would also cause PB disassembly to modulate cellular gene expression.