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Abstract：
Many proteins with intrinsically disordered regions interact with cytoplasmic ribosomes. However, many of the molecular functions related to these interactions are unclear. In this study, using an abundant RNA-binding protein with a structurally well-defined RNA recognition motif and an intrinsically disordered RGG domain as a model system, we investigated how this protein modulates mRNA storage and translation. Using genomic and molecular approaches, we show that the presence of Sbp1 slows ribosome movement on cellular mRNAs and promotes polysome stalling. Sbp1-associated polysomes display a ring-shaped structure in addition to a beads-on-string morphology visualized under electron microscope. Moreover, post-translational modifications at the RGG motif play important roles in directing cellular mRNAs to either translation or storage. Finally, binding of Sbp1 to the 5\'UTRs of mRNAs represses both cap-dependent and cap-independent translation initiation of proteins functionally important for general protein synthesis in the cell. Taken together, our study demonstrates an intrinsically disordered RNA binding protein regulates mRNA translation and storage via distinctive mechanisms under physiological conditions and establishes a framework with which functions of important RGG-proteins can be investigated and defined.
摘要：
许多具有内在无序区域的蛋白质与胞质核糖体相互作用。然而,与这些相互作用相关的许多分子功能尚不清楚。在这项研究中,使用具有结构明确的RNA识别基序和固有无序的RGG结构域的丰富RNA结合蛋白作为模型系统，我们研究了这种蛋白质如何调节mRNA的储存和翻译。使用基因组和分子方法，我们表明Sbp1的存在减缓了核糖体在细胞mRNA上的运动并促进了多体停滞。Sbp1相关的多聚体除了在电子显微镜下可视化的串珠形态外，还显示出环形结构。此外，RGG基序的翻译后修饰在指导细胞mRNA翻译或储存中起重要作用。最后,Sbp1与mRNAs的5'UTR的结合抑制了对细胞中一般蛋白质合成功能重要的蛋白质的帽依赖性和帽依赖性翻译起始。一起来看,我们的研究表明,一种内在无序的RNA结合蛋白在生理条件下通过独特的机制调节mRNA的翻译和储存,并建立了一个框架,利用该框架可以研究和定义重要的RGG蛋白的功能.
