Modulation of protein activities by reversible post-translational modifications (PTMs) is a major molecular mechanism involved in the control of virtually all cellular processes. One of these PTMs is ubiquitination, which regulates key processes including protein degradation, cell cycle, DNA damage repair, and signal transduction. Because of its importance for numerous cellular functions, ubiquitination has become an intense topic of research in recent years, and proteomics tools have greatly facilitated the identification of many ubiquitination targets. Taking advantage of the StUbEx strategy for exchanging the endogenous ubiquitin with an epitope-tagged version, we created a modified system, StUbEx PLUS, which allows precise mapping of ubiquitination sites by mass spectrometry. Application of StUbEx PLUS to U2OS cells treated with proteasomal inhibitors resulted in the identification of 41 589 sites on 7762 proteins, which thereby revealed the ubiquitous nature of this PTM and demonstrated the utility of the approach for comprehensive ubiquitination studies at site-specific resolution.

中文翻译：

---

StUbEx PLUS-改良的稳定标记的泛素交换系统，用于肽水平的纯化和泛素化位点的深度映射

通过可逆的翻译后修饰（PTM）调节蛋白质活性是参与几乎所有细胞过程控制的主要分子机制。这些PTM之一是泛素化，它调节关键过程，包括蛋白质降解，细胞周期，DNA损伤修复和信号转导。由于泛素化对众多细胞功能的重要性，因此近年来泛素化已成为研究的热点话题，蛋白质组学工具极大地促进了许多泛素化靶标的鉴定。利用StUbEx策略以表位标记的版本交换内源性泛素，我们创建了一个改良的系统StUbEx PLUS，该系统可通过质谱法精确定位泛素化位点。