Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada; Beijing Key Laboratory of DNA Damage Response and College of Life Sciences, Capital Normal University, Beijing 100048, China.
Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada.
Cell Signal. 2020 Oct;74:109712. doi: 10.1016/j.cellsig.2020.109712. Epub 2020 Jul 11.
The ubiquitin (Ub)-conjugating enzyme variants (Uev) Uev1A and Mms2 interact with Ubc13 to form heterodimeric complexes with different biological functions. Uev1A-Ubc13 is involved in NF-κB activation while Mms2-Ubc13 is required for the DNA-damage response. The structural comparison of the core domains of these two Uevs reveals no obvious difference, suggesting that the amino terminal extension of Uev1A plays a critical role in the functional determination. Indeed, truncated Uev1A lacking the N-terminal extension behaves like Mms2, while a chimeric protein containing the N-terminal Uev1A fused to Mms2 functionally resembles Uev1A. Interestingly, the N-terminal extension of Uev1A also dictates whether to assemble di- or poly-Ub chains in an in vitro reaction. Both thermodynamic measurements and enzymatic assays revealed that the Uev1A N-terminal extension weakens the Uev-Ubc13 interaction; however, other means capable of causing a reduced Uev1A-Ubc13 affinity and poly-Ub chain assembly do not necessarily promote NF-κB activation, indicating that the poly-Ub chain formation is not the only component contributed by the N-terminal extension of Uev1A. The physiological relevance of the Uev1A N-terminal truncation is presented and discussed.
泛素（Ub）连接酶变体（Uev）Uev1A 和 Mms2 与 Ubc13 相互作用形成具有不同生物学功能的异二聚体复合物。Uev1A-Ubc13 参与 NF-κB 激活，而 Mms2-Ubc13 则是 DNA 损伤反应所必需的。这两种 Uev 的核心结构域的结构比较没有明显差异，表明 Uev1A 的氨基末端延伸在功能决定中起着关键作用。事实上，缺乏氨基末端延伸的截短 Uev1A 表现得像 Mms2，而包含与 Mms2 融合的氨基末端 Uev1A 的嵌合蛋白在功能上类似于 Uev1A。有趣的是，Uev1A 的氨基末端延伸也决定了在体外反应中是否组装二聚体或多聚体 Ub 链。热力学测量和酶促测定都表明，Uev1A 氨基末端延伸削弱了 Uev-Ubc13 相互作用；然而，其他能够降低 Uev1A-Ubc13 亲和力和多聚 Ub 链组装的方法并不一定促进 NF-κB 激活，这表明多聚 Ub 链的形成不是 Uev1A 氨基末端延伸贡献的唯一组成部分。本文介绍并讨论了 Uev1A 氨基末端截短的生理相关性。
