Deciphering the folding pathways and predicting the structures of complex three-dimensional biomolecules is central to elucidating biological function. RNA is single-stranded, which gives it the freedom to fold into complex secondary and tertiary structures. These structures endow RNA with the ability to perform complex chemistries and functions ranging from enzymatic activity to gene regulation. Given that RNA is involved in many essential cellular processes, it is critical to understand how it folds and functionsin vivo. Within the last few years, methods have been developed to probe RNA structuresin vivoand genome-wide. These studies reveal that RNA often adopts very different structuresin vivoandin vitro, and provide profound insights into RNA biology. Nonetheless, bothin vitroandin vivoapproaches have limitations: studies in the complex and uncontrolled cellular environment make it difficult to obtain insight into RNA folding pathways and thermodynamics, and studiesin vitrooften lack direct cellular relevance, leaving a gap in our knowledge of RNA foldingin vivo. This gap is being bridged by biophysical and mechanistic studies of RNA structure and function under conditions that mimic the cellular environment. To date, most artificial cytoplasms have used various polymers as molecular crowding agents and a series of small molecules as cosolutes. Studies under suchin vivo-likeconditions are yielding fresh insights, such as cooperative folding of functional RNAs and increased activity of ribozymes. These observations are accounted for in part by molecular crowding effects and interactions with other molecules. In this review, we report milestones in RNA foldingin vitroandin vivoand discuss ongoing experimental and computational efforts to bridge the gap between these two conditions in order to understand how RNA folds in the cell.

中文翻译：

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弥合体外和体内RNA折叠之间的差距

破译折叠途径和预测复杂的三维生物分子的结构是阐明生物功能的核心。RNA是单链的，这使它可以自由折叠成复杂的二级和三级结构。这些结构赋予 RNA 执行从酶活性到基因调控的复杂化学和功能的能力。鉴于 RNA 参与许多重要的细胞过程，了解它如何折叠和发挥作用至关重要体内. 在过去的几年里，已经开发了探测 RNA 结构的方法体内和全基因组。这些研究表明，RNA通常采用非常不同的结构体内和体外，并提供对 RNA 生物学的深刻见解。尽管如此，两者体外和体内方法有局限性：在复杂和不受控制的细胞环境中的研究使得难以深入了解 RNA 折叠途径和热力学，以及研究体外通常缺乏直接的细胞相关性，在我们对 RNA 折叠的认识上留下了空白体内. 在模拟细胞环境的条件下，对 RNA 结构和功能的生物物理和机制研究正在弥合这一差距。迄今为止，大多数人工细胞质都使用各种聚合物作为分子聚集剂，并使用一系列小分子作为共溶质。在这样的研​​究体内样条件正在产生新的见解，例如功能性 RNA 的协同折叠和核酶活性的增加。这些观察结果部分归因于分子拥挤效应和与其他分子的相互作用。在这篇综述中，我们报告了 RNA 折叠的里程碑体外和体内并讨论正在进行的实验和计算工作，以弥合这两种情况之间的差距，以了解 RNA 如何在细胞中折叠。