The fusion oncoprotein Bcr-Abl is mostly located in the cytoplasm, which causes chronic myeloid leukemia (CML). After moving into the nucleus, the fusion protein can induce apoptosis of CML cells. The coiled-coil domain (CC domain) of Bcr-Abl protein plays a central role in the subcellular localization. However, how CC domain affects subcellular localization of Bcr-Abl remains unclear. Herein, the key proteins interacting with the Bcr-Abl CC domain were screened by immunoprecipitation binding mass spectrometry. The specific site of Bcr-Abl CC domain binding to target protein was predicted by Deep Viewer. Immunoprecipitation assay was used to confirmed the specific sites of protein binding. IF and western blot were used to observe the subcellular localization of target protein. Western blot was used to examine the protein changes. CCK-8, clonal formation test and FCM cycle detection were used to observe the effect of inhibitor on the proliferation ability of CML cells. FCM apoptosis detection was used to observe the level of cells apoptosis. HSP90AB1 interacts with Bcr-Abl CC domain via N-terminal domain (NTD), preventing the transport of Bcr-Abl protein to the nucleus and maintaining the activation of Bcr-Abl tyrosine kinase. The nucleus-entrapped Bcr-Abl markedly inhibits the proliferation and induces apoptosis of CML cells by activating p73 and repressing the expression of cytoplasmic oncogenic signaling pathways mediated by Bcr-Abl. Moreover, the combination of 17AAG (Tanespimycin) with Leptomycin B (LMB) considerably decreased the proliferation of CML cells. Our study provides evidence that it is feasible to transport Bcr-Abl into the nucleus as an alternative strategy for the treatment of CML, and targeting the NTD of HSP90AB1 to inhibit the interaction with Bcr-Abl is more accurate for the development and application of HSP90 inhibitor in the treatment of CML and other Bcr-Abl-addicted malignancies.

中文翻译：

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HSP90AB1与CC结构域相互作用对慢性粒细胞白血病细胞Bcr-Abl蛋白胞质定位及功能的影响

融合癌蛋白 Bcr-Abl 主要位于细胞质中，导致慢性粒细胞白血病 (CML)。进入细胞核后，融合蛋白可诱导CML细胞凋亡。Bcr-Abl 蛋白的卷曲螺旋结构域（CC 结构域）在亚细胞定位中起核心作用。然而，CC 结构域如何影响 Bcr-Abl 的亚细胞定位仍不清楚。在此，通过免疫沉淀结合质谱法筛选与 Bcr-Abl CC 结构域相互作用的关键蛋白。Deep Viewer 预测了 Bcr-Abl CC 结构域与靶蛋白结合的特定位点。免疫沉淀测定用于确认蛋白质结合的特定位点。IF和western印迹用于观察靶蛋白的亚细胞定位。Western印迹用于检查蛋白质变化。CCK-8, 采用克隆形成试验和FCM循环检测观察抑制剂对CML细胞增殖能力的影响。FCM凋亡检测用于观察细胞凋亡水平。HSP90AB1 通过 N 末端结构域 (NTD) 与 Bcr-Abl CC 结构域相互作用，阻止 Bcr-Abl 蛋白转运至细胞核并维持 Bcr-Abl 酪氨酸激酶的激活。包核的 Bcr-Abl 通过激活 p73 和抑制 Bcr-Abl 介导的细胞质致癌信号通路的表达，显着抑制 CML 细胞的增殖和诱导凋亡。此外，17AAG (Tanespimycin) 与细霉素 B (LMB) 的组合显着降低了 CML 细胞的增殖。