From the Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907.
From the Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907
J Biol Chem. 2018 Mar 16;293(11):3892-3903. doi: 10.1074/jbc.RA117.001065. Epub 2018 Jan 26.
The mammalian SWI/SNF chromatin remodeling complex is a heterogeneous collection of related protein complexes required for gene regulation and genome integrity. It contains a central ATPase (BRM or BRG1) and various combinations of 10-14 accessory subunits (BAFs for RM/BRG1 ssociated actor). Two distinct complexes differing in size, BAF and the slightly larger polybromo-BAF (PBAF), share many of the same core subunits but are differentiated primarily by having either AT-rich interaction domain 1A/B (ARID1A/B in BAF) or ARID2 (in PBAF). Using density gradient centrifugation and immunoprecipitation, we have identified and characterized a third and smaller SWI/SNF subcomplex. We termed this complex GBAF because it incorporates two mutually exclusive paralogs, GLTSCR1 (glioma tumor suppressor candidate region gene 1) or GLTSCR1L (GLTSCR1-like), instead of an ARID protein. In addition to GLTSCR1 or GLTSCR1L, the GBAF complex contains BRD9 (bromodomain-containing 9) and the BAF subunits BAF155, BAF60, SS18, BAF53a, and BRG1/BRM. We observed that GBAF does not contain the core BAF subunits BAF45, BAF47, or BAF57. Even without these subunits, GBAF displayed ATPase activity and bulk chromatin affinity comparable to those of BAF. GBAF associated with BRD4, but, unlike BRD4, the GBAF component GLTSCR1 was not required for the viability of the LNCaP prostate cancer cell line. In contrast, or knockouts in the metastatic prostate cancer cell line PC3 resulted in a loss in proliferation and colony-forming ability. Taken together, our results provide evidence for a compositionally novel SWI/SNF subcomplex with cell type-specific functions.
哺乳动物的 SWI/SNF 染色质重塑复合物是一种由相关蛋白组成的异质集合体，对于基因调控和基因组完整性至关重要。它包含一个中央 ATP 酶（BRM 或 BRG1）和 10-14 种不同的辅助亚基（与 RM/BRG1 相关的因子的 BAF）。两种不同大小的复合物，BAF 和稍大的多溴化 BAF（PBAF），在大小上有所不同，它们共享许多相同的核心亚基，但主要通过含有富含 AT 的相互作用域 1A/B（BAF 中的 ARID1A/B）或 ARID2（PBAF 中的 ARID2）来区分。通过密度梯度离心和免疫沉淀，我们已经鉴定并表征了第三种也是更小的 SWI/SNF 亚复合物。我们将这个复合物命名为 GBAF，因为它包含两个相互排斥的同源物，GLTSCR1（神经胶质瘤肿瘤抑制候选区基因 1）或 GLTSCR1L（GLTSCR1 样），而不是 ARID 蛋白。除了 GLTSCR1 或 GLTSCR1L，GBAF 复合物还包含 BRD9（含有溴结构域的蛋白 9）和 BAF 亚基 BAF155、BAF60、SS18、BAF53a 和 BRG1/BRM。我们观察到，GBAF 不包含核心 BAF 亚基 BAF45、BAF47 或 BAF57。即使没有这些亚基，GBAF 仍然表现出与 BAF 相当的 ATP 酶活性和整体染色质亲和力。GBAF 与 BRD4 相关，但与 BRD4 不同的是，GBAF 组件 GLTSCR1 对于 LNCaP 前列腺癌细胞系的存活不是必需的。相比之下，在转移性前列腺癌细胞系 PC3 中敲除 或 会导致增殖和集落形成能力丧失。总之，我们的研究结果为具有细胞类型特异性功能的组成上新颖的 SWI/SNF 亚复合物提供了证据。
