Molecular mechanisms underlying the epigenetic dysregulation by synovial sarcoma specific fusion oncoprotein

我们一直试图阐明FZD 10基因在滑膜肉瘤（synovial sarcomas，SS）中转录失调的分子机制，发现FZD 10基因启动子区的组蛋白乙酰化与FZD 10在SS中的上调密切相关。因此，我们接下来的目标是确定负责此的组蛋白乙酰转移酶（HAT）。采用pull-down法和Western blotting法，成功鉴定出SS 18-SSX相互作用的两个HAT（SSIH 1和SSIH 2）。此外，通过使用SSIH 1和SSIH 2的显性阴性（DN）形式，我们已经证明SS细胞中SSIH（DN）的异位表达废除了FZD 10的表达。这一结果表明SSIH 1和SSIH 2在功能上参与了SS中FZD 10的上调。然而，ChIP检测显示，在体内只有SSHI 1占据FZD 10启动子区域。总的来说，我们已经确定SSIH 1是负责SS中FZD 10失调的HAT。

We have been trying to unravel the molecular mechanism underlying the transcriptional dysregulation of FZD10 gene in synovial sarcomas (SSs) and have found that histone acetylation of the promoter region of FZD10 strongly correlates with up-regulation of FZD10 in SS. So, we next aimed to identify the histone acetyltransferase (HAT) responsible for this. By adopting pull-down assay followed by Western blotting, we succeeded to identify two HATs (designated as SSIH1 and 2) as the interactors of SS18-SSX. Furthermore, by using dominant-negative (DN) forms of SSIH1 and SSIH2, we have demonstrated that ectopic expression of SSIH(DN) in SS cells abrogated the expression of FZD10. This result indicates SSIH1 and SSIH2 are functionally involved in up-regulation of FZD10 in SSs, However, ChIP assay revealed that only SSHI1 occupies the FZD10 promoter region in vivo. Collectively, We have identified SSIH1 as the HAT responsible for the FZD10 dysregulation in SSs.