Ubiquitination, one type of the most common post-translational modification, mediates the regulation of protein homeostasis in vivo. Since ubiquitin itself contains multiple lysine residues and one N-terminal free amino group, eight types of ubiquitin chains can be formed. The K27 ubiquitin chain is formed through the ubiquitination of the ubiquitin Lys27 (K27), which adopts a compact conformation. In recent years, biological function of the K27 ubiquitin chain in innate immunity, protein homeostasis and DNA damage has been discovered, but the molecular mechanisms of K27 ubiquitin chain assembly, recognition and hydrolysis are still poorly understood. Here we review the structural features and biological functions of K27 ubiquitin chain, to provide a reference for future studies.
泛素化修饰作为最普遍存在的翻译后修饰形式之一，介导了生物体内蛋白质稳态调控等功能。泛素分子的7 个赖氨酸和N 端甲硫氨酸可以继续被泛素分子修饰，进而形成8 种类型的泛素链。其中，K48 和K63 泛素链由于丰度高且功能研究相对清楚被称为经典泛素链，而其他6 种泛素链被称为非经典泛素链。在非经典泛素链中，K27 泛素链是在泛素分子的Lys27 (K27) 位点上继续发生泛素化形成的，具有紧密的空间结构。近些年，K27泛素链在固有免疫、蛋白稳态和DNA 损伤修复等方面的功能逐渐被报道，但K27 泛素链的合成、修剪过程及其下游招募特定蛋白质的分子调控机制还所知甚少。文中结合实验室研究，综述了K27 泛素链结构特征、结合方式和生物学功能，为未来K27 泛素链结构和生物学功能的深入研究提供参考。.
Keywords: DNA damage; K27 ubiquitin chain; immunity; ubiquitin.