Honsei Norikazu, Ikuta Togo, Kawana Katsuyoshi, Kaneko Yasuhiko, Kawajiri Kaname
Research Institute for Clinical Oncology, Saitama Cancer Center, Ina, Saitama 362-0806, Japan.
Int J Oncol. 2006 Sep;29(3):689-93.
A t(11;22)(q24;q12) translocation is present in 90% of Ewing's sarcoma, and results in the formation of the EWS-FLI1 fusion gene encoding an oncogenic transcription factor. To clarify the function of chimeric EWS-FLI1 proteins, an identification of a nuclear localization signal (NLS) in the EWS, FLI1 and EWS-FLI1 proteins is important because the chimeric oncoprotein may lose or gain NLS function different from native proteins resulting in different subcellular localization, and in deregulated gene expression. Furthermore, some studies reported that patients with one type of fusion gene ('type 1') had better overall survival than those with other types, suggesting that functional differences may be present among various fusion proteins. There has been only one study reporting a NLS in EWS, but none reporting those in FLI1 and EWS-FLI1. To clarify the molecular mechanisms of Ewing tumor development, we first identified the NLSs of EWS and FLI1. We allocated the NLS to amino acid residues 632-656 near the C-terminal region of EWS that is different from the previous study, and identified two NLSs of FLI1, NLS1 (63-90) in the N-terminal domain and NLS2 (319-360) in the 3'-ETS domain. In addition, the present study showed that all of the EWS-FLI1 fusion proteins completely reside in the nucleus without affecting the frequency of nuclear localization among variants, suggesting that NLS2 of FLI1 was used for nuclear translocation of various EWS-FLI1 fusion proteins.
90%的尤因肉瘤存在t(11;22)(q24;q12)易位，这导致编码致癌转录因子的EWS-FLI1融合基因的形成。为了阐明嵌合EWS-FLI1蛋白的功能，鉴定EWS、FLI1和EWS-FLI1蛋白中的核定位信号（NLS）很重要，因为嵌嵌嵌致癌嵌合蛋白可能失去或获得与天然蛋白不同的NLS功能，从而导致不同的亚细胞定位和基因表达失调。此外，一些研究报告称，携带一种融合基因（“1型”）的患者总体生存率高于携带其他类型融合基因的患者，这表明各种融合蛋白之间可能存在功能差异。仅有一项研究报道了EWS中的NLS，但没有关于FLI1和EWS-FLI1中NLS的报道。为了阐明尤因肿瘤发生发展的分子机制，我们首先鉴定了EWS和FLI1的NLS。我们将EWS的NLS定位到靠近C端区域的632-656位氨基酸残基，这与之前的研究不同，并且鉴定出FLI1的两个NLS，位于N端结构域的NLS1（63-90）和位于3'-ETS结构域的NLS2（319-360）。此外，本研究表明，所有EWS-FLI1融合蛋白都完全定位于细胞核中，且不影响不同变体之间的核定位频率，这表明FLI1的NLS2用于各种EWS-FLI1融合蛋白的核转运。
