Institute of Agricultural and Nutritional Sciences, Martin Luther University Halle-Wittenberg, Halle, Germany; email:
Department of Biology, Queen's University, Kingston, Ontario, Canada; email:
Annu Rev Plant Biol. 2022 May 20;73:93-121. doi: 10.1146/annurev-arplant-102720-012310. Epub 2022 Feb 28.
Posttranslational modifications add complexity and diversity to cellular proteomes. One of the most prevalent modifications across eukaryotes is ubiquitination, which is orchestrated by E3 ubiquitin ligases. U-box-containing E3 ligases have massively expanded in the plant kingdom and have diversified into plant U-box proteins (PUBs). PUBs likely originated from two or three ancestral forms, fusing with diverse functional subdomains that resulted in neofunctionalization. Their emergence and diversification may reflect adaptations to stress during plant evolution, reflecting changes in the needs of plant proteomes to maintain cellular homeostasis. Through their close association with protein kinases, they are physically linked to cell signaling hubs and activate feedback loops by dynamically pairing with E2-ubiquitin-conjugating enzymes to generate distinct ubiquitin polymers that themselves act as signals. Here, we complement current knowledgewith comparative genomics to gain a deeper understanding of PUB function, focusing on their evolution and structural adaptations of key U-box residues, as well as their various roles in plant cells.
翻译后修饰增加了细胞蛋白质组的复杂性和多样性。泛素化是真核生物中最普遍的修饰之一，由E3泛素连接酶精心调控。含U-box的E3连接酶在植物界大量扩增，并分化为植物U-box蛋白（PUB）。PUB可能起源于两到三种祖先形式，与多种功能亚结构域融合，导致了新功能化。它们的出现和分化可能反映了植物进化过程中对压力的适应，体现了植物蛋白质组维持细胞内稳态需求的变化。通过与蛋白激酶的紧密关联，它们与细胞信号枢纽物理相连，并通过与E2泛素结合酶动态配对来激活反馈回路，从而生成独特的泛素聚合物，这些聚合物本身就充当信号。在这里，我们通过比较基因组学来补充现有知识，以更深入地了解PUB的功能，重点关注它们的进化、关键U-box残基的结构适应性以及它们在植物细胞中的各种作用。
