Phosphorylation of Ser1452 on BRG1 inhibits the function of the SWI/SNF complex in chromatin activation
Phosphorylation of Ser1452 on BRG1 inhibits the function of the SWI/SNF complex in chromatin activation
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BRG1 上 Ser1452 的磷酸化抑制 SWI/SNF 复合物在染色质激活中的功能
DOI：
10.1016/j.jprot.2021.104319
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发表时间：
2021
影响因子：
3.3
通讯作者：
Hirano Hisashi
中科院分区：
文献类型：
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作者：
Kimura Ayuko;Arakawa Noriaki;Kagawa Hiroyuki;Kimura Yayoi;Hirano Hisashi
BRG1是SWI/SNF染色质重塑复合体的核心亚单位之一，在癌症中经常发生突变。在此之前，我们报道了来自卵巢透明细胞癌的细胞系中BRG1在Ser1452(<；10%)上的磷酸化水平显著下调，这些细胞系经常复发和获得性耐药。在这项研究中，我们试图利用表达野生型、磷酸化模拟(BRG1-S1452D)或非磷酸化(BRG1-S1452A)BRG1的细胞株来阐明BRG1磷酸化的作用。定量蛋白质组学分析显示，在Brg1-S1452D细胞中，与连接蛋白H1s、组蛋白甲基化和蛋白泛素化相关的蛋白质和磷蛋白表达上调，这可能协调地促进了目标蛋白的染色质失活和泛素依赖的降解。与这些结果一致的是，BRG1-S1452D细胞显示出浓缩的染色质和多泛素化蛋白的增加。在brg1-S1452D细胞中，我们还检测到各种癌症相关蛋白(如EGFR和MET)的下调，以及迁移、增殖和对紫杉烷和奥沙利铂敏感性的降低。综上所述，我们的结果揭示了BRG1的磷酸化通过抑制SWI/SNF复合体在染色质激活中的功能，从而促进了多种癌症相关蛋白的表达，从而推动了肿瘤的恶性发展。意义我们首次证明了SWI/SNF染色质重塑复合体的组成部分BRG1的Ser1452磷酸化位点的突变改变了连接蛋白H1s、组蛋白H1s的结合竞争对手组蛋白H1s以及参与异染色组蛋白修饰的组蛋白甲基化酶/去甲基酶的蛋白和磷蛋白水平，从而促进了染色质的失活。在磷酸化模拟突变体中，检测到各种癌症相关蛋白的显著减少，以及迁移、增殖和对特定抗肿瘤药物的敏感性。我们的结果表明，BRG1的磷酸化通过抑制SWI/SNF复合体在染色质激活中的功能，从而促进多种癌症相关蛋白的表达，从而推动肿瘤的恶性转化。
BRG1, one of core subunits of the SWI/SNF chromatin remodeling complex, is frequently mutated in cancers. Previously, we reported significant downregulation of the phosphorylation level of BRG1 on Ser1452(<10%) in cell lines derived from ovarian clear cell carcinoma with frequent recurrence and acquired drug resistance. In this study, we tried to elucidate the roles of BRG1 phosphorylation, using cell lines expressing wild-type, phosphorylation-mimic (brg1-S1452D), or non-phosphorylatable (brg1-S1452A) BRG1. Quantitative proteomic analyses revealed upregulation of proteins and phosphoproteins related to linker histone H1s, histone methylation, and protein ubiquitylation inbrg1-S1452D cells, which may coordinately promote the chromatin inactivation and ubiquitin-dependent degradation of target proteins. Consistent with these results,brg1-S1452D cells exhibited an increase in condensed chromatin and polyubiquitylated proteins. Inbrg1-S1452D cells, we also detected downregulation of various cancer-related proteins (e.g., EGFR and MET) as well as decreased migration, proliferation, and sensitivity to taxanes and oxaliplatin. Together, our results reveal that BRG1 phosphorylation drives tumor malignancy by inhibiting the functions of SWI/SNF complex in chromatin activation, thereby promoting expression of various cancer-related proteins.SignificanceFor the first time we demonstrated that the mutation on Ser1452phosphorylation site of BRG1, a component of SWI/SNF chromatin remodeling complex, changed protein and phosphoprotein levels of linker histone H1s, binding competitor of histone H1s, and histone methylase/demethylase involved in the heterochromatic histone modifications to promote the chromatin inactivation. In phosphorylation-mimic mutant, significant decrease of various cancer-related proteins as well as migration, proliferation, and sensitivity to specific antitumor agents were detected. Our results reveal that BRG1 phosphorylation drives tumor malignancy by inhibiting the functions of SWI/SNF complex in chromatin activation, thereby promoting expression of various cancer-related proteins.