A KRAB-related domain and a novel transcription repression domain in proteins encoded by SSX genes that are disrupted in human sarcomas
A KRAB-related domain and a novel transcription repression domain in proteins encoded by SSX genes that are disrupted in human sarcomas
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DOI：
10.1038/sj.onc.1202122
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发表时间：
1998-10-15
期刊：
影响因子：
8
通讯作者：
Knight, JC
中科院分区：
文献类型：
--
作者：
Lim, FL;Soulez, M;Knight, JC
SSX基因显示出广泛的核苷酸序列保守性，但对其功能知之甚少。通过染色体易位和与SYT的“框内”融合，SSX 1或SSX 2的破坏是滑膜肉瘤的一致特征。所产生的SYT-SSX 1/SSX 2蛋白是转录的激活剂;反式激活功能位于SYT中，未重排的SSX 1可以抑制转录，并且这已归因于N末端的推定Kruppel相关盒（KRAB）抑制结构域。在这里，我们分离了SSX-KRAB结构域，以专门测量阻遏活性，使用先前表征的KOX 1-KRAB结构域作为对照。在我们的阻遏物测定中，SSX 1-和SSX 2-KRAB结构域下调报告基因的反式激活3倍，而KOX 1-KRAB在测定中达到83倍的阻遏。酵母双杂交分析表明，SSX 1-KRAB与KOX 1-KRAB不同，不能与KRAB共阻遏物TIF 1 β相互作用。这些结果提出了关于SSX-KRAB和Kruppel锌指基因的典型KRAB结构域的进化和功能关系的问题。我们发现，全长SSX 1在我们的阻遏物测定中显示出有效的（74倍）阻遏，表明存在不同于SSX-KRAB的阻遏结构域。通过测定SSX 1的缺失构建体，我们将阻遏活性定位于C末端的33个氨基酸。该新结构域在SSX家族成员之间是保守的，并且与KRAB相关结构域不同，其在与SYT融合时被保留。这对于理解SYT-SSX融合蛋白可促成瘤形成的机制具有重要意义。
SSX genes show extensive nucleotide sequence conservation but little is known of their function. Disruption of SSX1 or SSX2, by chromosome translocation and 'in-frame' fusion to SYT, is a consistent feature of synovial sarcomas, The resulting SYT-SSX1/SSX2 proteins are activators of transcription; transactivation function is located in SYT, Unrearranged SSX1 can repress transcription, and this has been attributed to a putative Kruppel associated box (KRAB) repression domain at the N-terminus. Here we isolated SSX-KRAB domains to specifically measure repression activity, using a previously characterized KOX1-KRAB domain as a control. In our repressor assay SSX1- and SSX2-KRAB domains down-modulated the transactivation of reporter gene by threefold, compared with 83-fold repression achieved by KOX1-KRAB in the assay. Yeast two-hybrid analysis showed that SSX1-KRAB, unlike KOX1-KRAB, fails to interact with the KRAB co-repressor TIF1 beta. These results raise questions about the evolutionary and functional relationship of SSX-KRAB and typical KRAB domains of Kruppel zinc finger genes. We found that full-length SSX1 showed potent (74-fold) repression in our repressor assay, indicating the existence of a repression domain distinct from SSX-KRAB. By assaying deletion constructs of SSX1 we localized repression activity to 33 amino acids at the C-terminus. This novel domain is conserved between SSX family members, and, unlike the KRAB-related domain, is retained on fusion with SYT, This has important implications in understanding the mechanism by which the SYT-SSX fusion protein could contribute to neoplasia.