背景：泛素化机制的阐明带来了治疗胶质母细胞瘤（GBM）的新方法。三联基序（TRIM）蛋白介导可逆、严格的泛素化，与神经胶质瘤恶性肿瘤密切相关。本研究旨在筛选三联基序蛋白中最重要、最异常的调节成分，并探讨其潜在机制。方法：通过数据库以多维方式将TRIM21确定为加速胶质瘤细胞进展的重要癌基因，并在人体样本和细胞中得到证实。进行串联质量标签 (TMT) 和 MS 分析以发现 TRIM21 的底物。通过 CO-IP、荧光素酶报告基因测定以及功能获得和丧失测定进一步研究其潜在机制。应用 siRNA 体内治疗来评估 TRIM21 的治疗意义。结果：我们筛选了一组 TRIM 蛋白，并鉴定了 TRIM21、一种 E3 泛素蛋白连接酶和自身抗原，以及 GBM 的预后生物标志物。从功能上讲，野生型 TRIM21 的高表达可加速体外和体内肿瘤的进展，而 TRIM21 突变体（包括具有关键环指缺失的突变体）则不会。从机制上讲，TRIM21 刺激 K63 连接的泛素化和活性 β-catenin 从细胞质到细胞核的亚细胞易位。此外，TRIM21 与细胞核中的 β-连环蛋白上游调节因子 TIF1γ 形成复合物，并通过在 K5 位点诱导 K48 连接的泛素化来加速其降解，从而进一步增加核内 β-连环蛋白的存在。在神经胶质瘤组织微阵列实验中，发现内源性 TRIM21 水平与 TIF1γ 呈负相关，但与 β-catenin 呈正相关。此外，将TRIM21小干扰RNA（siRNA）直接注射到U87细胞来源的肿瘤中（用siRNA进行体内治疗）被证明可以抑制裸鼠中的肿瘤生长。结论：这项工作表明 TRIM21/TIF1γ/β-catenin 轴参与人类 GBM 的进展。 TRIM21 是一种有前途的治疗和预后生物标志物，用于治疗β-连环蛋白过度活跃的神经胶质瘤。© 作者。

Background: Elucidation of the mechanism of ubiquitation has led to novel ways to treat glioblastoma (GBM). A tripartite motif (TRIM) protein mediates a reversible, stringent ubiquitation which is closely related to glioma malignancy. This study intends to screen the most vital and abnormal regulating component of the tripartite motif protein and to explore its underlying mechanisms. Methods: TRIM21 is identified as an important oncogene that accelerates the progression of glioma cell through database in a multidimensional way and this is confirmed in human samples and cells. Tandem Mass Tags (TMT) and MS analysis are performed to discover the substrates of TRIM21.The underlying mechanisms are further investigated by CO-IP, luciferase reporter assays and gain and loss of function assays. In vivo treatment with siRNA is applied to evaluate the therapeutic significance of TRIM21. Result: We screened a panel of TRIM proteins and identified TRIM21, a E3 ubiquitin-protein ligase and autoantigen, as well as a prognostic biomarker for GBM. Functionally, high expression of wild-type TRIM21 accelerates tumor progression in vitro and in vivo, whereas TRIM21 mutants, including one with a critical RING-finger deletion, do not. Mechanistically, TRIM21 stimulates K63-linked ubiquitination and subcellular translocation of active β-catenin from the cytoplasm to the nucleus. Moreover, TRIM21 forms a complex with the β-catenin upstream regulator, TIF1γ, in the nucleus and accelerated its degradation by inducing K48-linked ubiquitination at K5 site, consequently increasing further nuclear β-catenin presence. Endogenous TRIM21 levels are found to be inversely correlated with TIF1γ but positively correlated with β-catenin in glioma tissue microarray experiments. Furthermore, direct injection of TRIM21 small interfering RNA (siRNA) into U87 cell-derived tumors (in vivo treatment with siRNA) is proved to inhibit tumor growth in nude mice. Conclusion: This work suggests that TRIM21/TIF1γ/β-catenin axis is involved in the progression of human GBM. TRIM21 is a promising therapeutic and prognostic biomarker for glioma with hyperactive β-catenin.© The author(s).