Randall Centre for Cell & Molecular Biophysics, King's College London, Guy's Campus, London, UK.
Laboratoire De Biologie Intégrative Des Modèles Marins, Station Biologique De Roscoff, CNRS-Sorbonne Université, Roscoff, France.
RNA Biol. 2021 Feb;18(2):194-206. doi: 10.1080/15476286.2020.1733799. Epub 2020 Mar 18.
The La-related proteins (LaRPs) are a superfamily of eukaryotic RNA-binding proteins with important and varied roles. To understand LaRP functions it is essential to unravel the divergent features responsible for their RNA target selectivity, which underlie their distinct identities and cellular roles. LaRPs are built on a common structural module called the 'La-module' that acts as a main locus for RNA recognition. The La-module is comprised of two tethered domains whose relative structural and dynamic interplay has been proposed to regulate RNA-target selection, albeit the mechanistic underpinning of this recognition remains to be elucidated. A main unsolved conundrum is how conserved La-modules across LaRPs are able to bind to extremely diverse RNA ligands.In this work, we employed Small Angle X-ray Scattering (SAXS) to investigate several human LaRP La-modules in the absence and, where applicable, in the presence of their RNA target, with the aim to explore the structural dynamics of their RNA recognition and provide information on the architectural landscape accessible to these proteins. Integration of these SAXS experiments with prior X-ray crystallography and NMR data suggests that RNA binding is generally accompanied by a compaction and loss of flexibility of the La-module. Nonetheless, the La-modules appear to experience a considerably different degree of inherent flexibility in their apo state. Furthermore, although they all exist in discrete subsets of accessible populations in equilibrium, these vary from LaRP to LaRP and can be either extended or compact. We propose that these divergent features may be critical for RNA substrate discrimination.
La 相关蛋白（LaRPs）是一类真核 RNA 结合蛋白超家族，具有重要且多样的功能。为了了解 LaRP 的功能，必须揭示导致其 RNA 靶标选择性的不同特征，这是它们独特身份和细胞功能的基础。LaRPs 建立在一个称为“La 模块”的共同结构模块上，该模块充当 RNA 识别的主要位置。La 模块由两个连接的结构域组成，其相对结构和动态相互作用被提出用于调节 RNA 靶标选择，尽管这种识别的机制基础仍有待阐明。一个主要的未解之谜是，LaRPs 中保守的 La 模块如何能够结合极其多样化的 RNA 配体。在这项工作中，我们使用小角度 X 射线散射（SAXS）在不存在和（在适用的情况下）存在其 RNA 靶标的情况下研究了几种人类 LaRP La 模块，目的是探索其 RNA 识别的结构动力学，并提供有关这些蛋白质可访问的结构景观的信息。将这些 SAXS 实验与之前的 X 射线晶体学和 NMR 数据相结合表明，RNA 结合通常伴随着 La 模块的压缩和柔韧性丧失。尽管如此，La 模块在 apo 状态下似乎表现出相当不同程度的固有柔韧性。此外，尽管它们都存在于平衡的离散可及种群子集，但这些子集因 LaRP 而异，可以扩展或紧凑。我们提出，这些不同的特征可能是 RNA 底物区分的关键。
