Topors functions as an E3 ubiquitin ligase with specific E2 enzymes and ubiquitinates p53
Topors functions as an E3 ubiquitin ligase with specific E2 enzymes and ubiquitinates p53
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DOI：
10.1074/jbc.c400300200
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发表时间：
2004-08-27
影响因子：
4.8
通讯作者：
Rubin, EH
中科院分区：
文献类型：
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作者：
Rajendra, R;Malegaonkar, D;Rubin, EH
人类拓扑异构酶I和p53结合蛋白topors包含一个高度保守的n端c3hc4型RING结构域，该结构域与已知的E3泛素连接酶的RING结构域同源。我们证明topors在体外作为环依赖性E3泛素连接酶与E2酶UbcH5a、UbcH5c和UbcH6一起起作用，但不与UbcH7、CDC34或UbcH2b一起起作用。进一步的研究表明，topors RING结构域内的保守色氨酸是泛素化活性所必需的。此外，体外和细胞研究都表明p53是topors的泛素化底物。与MDM2类似，topors的过表达导致人骨肉瘤细胞系中p53蛋白表达的蛋白酶体依赖性降低。这些结果与最近果蝇topors同源物泛素化毛状转录抑制因子的发现相似，表明topors作为多种转录因子的泛素连接酶起作用。
The human topoisomerase I- and p53-binding protein topors contains a highly conserved, N-terminal C3HC4-type RING domain that is homologous to the RING domains of known E3 ubiquitin ligases. We demonstrate that topors functions in vitro as a RING-dependent E3 ubiquitin ligase with the E2 enzymes UbcH5a, UbcH5c, and UbcH6 but not with UbcH7, CDC34, or UbcH2b. Additional studies indicate that a conserved tryptophan within the topors RING domain is required for ubiquitination activity. Furthermore, both in vitro and cellular studies implicate p53 as a ubiquitination substrate for topors. Similar to MDM2, overexpression of topors results in a proteasome-dependent decrease in p53 protein expression in a human osteosarcoma cell line. These results are similar to the recent finding that a Drosophila topors orthologue ubiquitinates the Hairy transcriptional repressor and suggest that topors functions as a ubiquitin ligase for multiple transcription factors.