Institute for Microbiology, Cluster of Excellence on Plant Sciences, Heinrich Heine University Düsseldorf, Düsseldorf, Germany.
EMBO Rep. 2019 Sep;20(9):e47381. doi: 10.15252/embr.201847381. Epub 2019 Jul 24.
mRNA transport determines spatiotemporal protein expression. Transport units are higher-order ribonucleoprotein complexes containing cargo mRNAs, RNA-binding proteins and accessory proteins. Endosomal mRNA transport in fungal hyphae belongs to the best-studied translocation mechanisms. Although several factors are known, additional core components are missing. Here, we describe the 232 kDa protein Upa2 containing multiple PAM2 motifs (poly[A]-binding protein [Pab1]-associated motif 2) as a novel core component. Loss of Upa2 disturbs transport of cargo mRNAs and associated Pab1. Upa2 is present on almost all transport endosomes in an mRNA-dependent manner. Surprisingly, all four PAM2 motifs are dispensable for function during unipolar hyphal growth. Instead, Upa2 harbours a novel N-terminal effector domain as important functional determinant as well as a C-terminal GWW motif for specific endosomal localisation. In essence, Upa2 meets all the criteria of a novel core component of endosomal mRNA transport and appears to carry out crucial scaffolding functions.
mRNA 运输决定时空蛋白质表达。运输单元是含有货物 mRNA、RNA 结合蛋白和辅助蛋白的更高阶核糖核蛋白复合物。真菌菌丝体中的内体 mRNA 运输属于研究最充分的易位机制之一。尽管已经知道了几个因素，但仍缺少其他核心成分。在这里，我们将含有多个 PAM2 基序（多[A]结合蛋白 [Pab1]相关基序 2）的 232 kDa 蛋白 Upa2 描述为一种新型核心成分。Upa2 的缺失会干扰货物 mRNA 和相关 Pab1 的运输。Upa2 以 mRNA 依赖的方式存在于几乎所有的运输内体上。令人惊讶的是，在单极菌丝生长过程中，所有四个 PAM2 基序对于功能都是可有可无的。相反，Upa2 具有一个新型的 N 端效应结构域，作为重要的功能决定因素，以及一个 C 端 GWW 基序，用于特定的内体定位。从本质上讲，Upa2 满足内体 mRNA 运输新型核心成分的所有标准，并且似乎发挥着至关重要的支架功能。
