Zapata J M, Pawlowski K, Haas E, Ware C F, Godzik A, Reed J C
Burnham Institute, La Jolla, California 92037, USA.
J Biol Chem. 2001 Jun 29;276(26):24242-52. doi: 10.1074/jbc.M100354200. Epub 2001 Feb 21.
We have identified three new tumor necrosis factor-receptor associated factor (TRAF) domain-containing proteins in humans using bioinformatics approaches, including: MUL, the product of the causative gene in Mulibrey Nanism syndrome; USP7 (HAUSP), an ubiquitin protease; and SPOP, a POZ domain-containing protein. Unlike classical TRAF family proteins involved in TNF family receptor (TNFR) signaling, the TRAF domains (TDs) of MUL, USP7, and SPOP are located near the NH(2) termini or central region of these proteins, rather than carboxyl end. MUL and USP7 are capable of binding in vitro via their TDs to all of the previously identified TRAF family proteins (TRAF1, TRAF2, TRAF3, TRAF4, TRAF5, and TRAF6), whereas the TD of SPOP interacts weakly with TRAF1 and TRAF6 only. The TD of MUL also interacted with itself, whereas the TDs of USP7 and SPOP did not self-associate. Analysis of various MUL and USP7 mutants by transient transfection assays indicated that the TDs of these proteins are necessary and sufficient for suppressing NF-kappaB induction by TRAF2 and TRAF6 as well as certain TRAF-binding TNF family receptors. In contrast, the TD of SPOP did not inhibit NF-kappaB induction. Immunofluorescence confocal microscopy indicated that MUL localizes to cytosolic bodies, with targeting to these structures mediated by a RBCC tripartite domain within the MUL protein. USP7 localized predominantly to the nucleus, in a TD-dependent manner. Data base searches revealed multiple proteins containing TDs homologous to those found in MUL, USP7, and SPOP throughout eukaryotes, including yeast, protists, plants, invertebrates, and mammals, suggesting that this branch of the TD family arose from an ancient gene. We propose the moniker TEFs (TD-encompassing factors) for this large family of proteins.
我们运用生物信息学方法在人类中鉴定出三种新的含肿瘤坏死因子受体相关因子（TRAF）结构域的蛋白质，包括：MUL，即穆利布雷南斯综合征致病基因的产物；USP7（HAUSP），一种泛素蛋白酶；以及SPOP，一种含POZ结构域的蛋白质。与参与肿瘤坏死因子家族受体（TNFR）信号传导的经典TRAF家族蛋白质不同，MUL、USP7和SPOP的TRAF结构域（TDs）位于这些蛋白质的氨基末端附近或中央区域，而非羧基末端。MUL和USP7能够通过其TDs在体外与所有先前鉴定的TRAF家族蛋白质（TRAF1、TRAF2、TRAF3、TRAF4、TRAF5和TRAF6）结合，而SPOP的TD仅与TRAF1和TRAF6有微弱相互作用。MUL的TD也能与自身相互作用，而USP7和SPOP的TDs则不会自我缔合。通过瞬时转染实验对各种MUL和USP7突变体进行分析表明，这些蛋白质的TDs对于抑制TRAF2和TRAF6以及某些与TRAF结合的肿瘤坏死因子家族受体诱导的核因子κB是必需且充分的。相比之下，SPOP的TD不会抑制核因子κB的诱导。免疫荧光共聚焦显微镜检查表明，MUL定位于胞质小体，其靶向这些结构是由MUL蛋白内的RBCC三方结构域介导的。USP7主要以TD依赖的方式定位于细胞核。数据库搜索揭示，在整个真核生物中，包括酵母、原生生物、植物、无脊椎动物和哺乳动物，有多种蛋白质含有与MUL、USP7和SPOP中发现的TDs同源的TDs，这表明TD家族的这一分支起源于一个古老的基因。我们为这一大家族蛋白质提议使用“TEFs（含TD的因子）”这一名称。
