Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA.
Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA.
J Mol Biol. 2024 Sep 15;436(18):168703. doi: 10.1016/j.jmb.2024.168703. Epub 2024 Jul 14.
Stress granules (SGs) are large ribonucleoprotein assemblies that form in response to acute stress in eukaryotes. SG formation is thought to be initiated by liquid-liquid phase separation (LLPS) of key proteins and RNA. These molecules serve as a scaffold for recruitment of client molecules. LLPS of scaffold proteins in vitro is highly concentration-dependent, yet biomolecular condensates in vivo contain hundreds of unique proteins, most of which are thought to be clients rather than scaffolds. Many proteins that localize to SGs contain low-complexity, prion-like domains (PrLDs) that have been implicated in LLPS and SG recruitment. The degree of enrichment of proteins in biomolecular condensates such as SGs can vary widely, but the underlying basis for these differences is not fully understood. Here, we develop a toolkit of model PrLDs to examine the factors that govern efficiency of PrLD recruitment to stress granules. Recruitment was highly sensitive to amino acid composition: enrichment in SGs could be tuned through subtle changes in hydrophobicity. By contrast, SG recruitment was largely insensitive to PrLD concentration at both a population level and single-cell level. These observations point to a model wherein PrLDs are enriched in SGs through either simple solvation effects or interactions that are effectively non-saturable even at high expression levels.
应激颗粒（SGs）是真核生物响应急性应激而形成的大型核糖核蛋白体。SG 的形成被认为是由关键蛋白和 RNA 的液-液相分离（LLPS）引发的。这些分子充当招募客户分子的支架。体外支架蛋白的 LLPS 高度依赖于浓度，但体内生物分子凝聚体包含数百种独特的蛋白质，其中大多数被认为是客户而不是支架。许多定位于 SG 的蛋白质含有低复杂度的朊样结构域（PrLDs），这些结构域与 LLPS 和 SG 募集有关。生物分子凝聚体（如 SG）中蛋白质的富集程度差异很大，但这些差异的基础尚未完全了解。在这里，我们开发了一套模型 PrLD 工具包，以研究控制 PrLD 募集到应激颗粒效率的因素。募集对氨基酸组成非常敏感：通过轻微改变疏水性，可以调整 SG 中的富集。相比之下，在群体水平和单细胞水平上，PrLD 浓度对 SG 募集的影响都不大。这些观察结果表明，PrLD 通过简单的溶剂化作用或即使在高表达水平下也基本上非饱和的相互作用在 SG 中富集的模型。
