Molecular Structure of Cell Signalling Laboratory, The Francis Crick Institute, London, UK.
Molecular Structure of Cell Signalling Laboratory, The Francis Crick Institute, London, UK
Life Sci Alliance. 2019 Apr 26;2(3). doi: 10.26508/lsa.201900295. Print 2019 Jun.
TRIM E3 ubiquitin ligases regulate multiple cellular processes, and their dysfunction is linked to disease. They are characterised by a conserved N-terminal tripartite motif comprising a RING, B-box domains, and a coiled-coil region, with C-terminal domains often mediating substrate recruitment. TRIM proteins are grouped into 11 classes based on C-terminal domain identity. Class VI TRIMs, TRIM24, TRIM33, and TRIM28, have been described as transcriptional regulators, a function linked to their C-terminal plant homeodomain and bromodomain, and independent of their ubiquitination activity. It is unclear whether E3 ligase activity is regulated in family members where the C-terminal domains function independently. Here, we provide a detailed biochemical characterisation of the RING domains of class VI TRIMs and describe the solution structure of the TRIM28 RING. Our study reveals a lack of activity of the isolated RING domains, which may be linked to the absence of self-association. We propose that class VI TRIMs exist in an inactive state and require additional regulatory events to stimulate E3 ligase activity, ensuring that associated chromatin-remodelling factors are not injudiciously degraded.
TRIM E3 泛素连接酶调节多种细胞过程，其功能障碍与疾病有关。它们的特征是保守的 N 端三部分基序，包括一个 RING、B 盒结构域和一个卷曲螺旋区，C 端结构域通常介导底物募集。TRIM 蛋白根据 C 端结构域的同一性分为 11 类。TRIM24、TRIM33 和 TRIM28 等 6 类 TRIM 被描述为转录调节剂，其功能与 C 端植物同源结构域和溴结构域有关，与它们的泛素化活性无关。在 C 端结构域独立发挥作用的家族成员中，E3 连接酶活性是否受到调节尚不清楚。在这里，我们对 6 类 TRIM 的 RING 结构域进行了详细的生化表征，并描述了 TRIM28 RING 的溶液结构。我们的研究揭示了分离的 RING 结构域缺乏活性，这可能与缺乏自我缔合有关。我们提出，6 类 TRIM 处于非活性状态，需要额外的调节事件来刺激 E3 连接酶活性，以确保相关的染色质重塑因子不会被不当降解。
