Schulze Center for Novel Therapeutics, Division of Oncology Research, Schulze Center for Novel Therapeutics, Rochester, Minnesota, USA.
Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, USA.
J Biol Chem. 2020 Jun 26;295(26):8725-8735. doi: 10.1074/jbc.RA120.013268. Epub 2020 May 6.
The transcription factor GLI1 (GLI family zinc finger 1) plays a key role in the development and progression of multiple malignancies. To date, regulation of transcriptional activity at target gene promoters is the only molecular event known to underlie the oncogenic function of GLI1. Here, we provide evidence that GLI1 controls chromatin accessibility at distal regulatory regions by modulating the recruitment of SMARCA2 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 2) to these elements. We demonstrate that SMARCA2 endogenously interacts with GLI1 and enhances its transcriptional activity. Mapping experiments indicated that the C-terminal transcriptional activation domain of GLI1 and SMARCA2's central domains, including its ATPase motif, are required for this interaction. Interestingly, similar to SMARCA2, GLI1 overexpression increased chromatin accessibility, as indicated by results of the micrococcal nuclease assay. Further, results of assays for transposase-accessible chromatin with sequencing (ATAC-seq) after GLI1 knockdown supported these findings, revealing that GLI1 regulates chromatin accessibility at several regions distal to gene promoters. Integrated RNA-seq and ATAC-seq data analyses identified a subset of differentially expressed genes located in to these regulated chromatin sites. Finally, using the GLI1-regulated gene () as a model, we demonstrate that GLI1 and SMARCA2 co-occupy a distal chromatin peak and that SMARCA2 recruitment to this HHIP putative enhancer requires intact GLI1. These findings provide insights into how GLI1 controls gene expression in cancer cells and may inform approaches targeting this oncogenic transcription factor to manage malignancies.
转录因子 GLI1(GLI 家族锌指蛋白 1)在多种恶性肿瘤的发生和发展中起着关键作用。迄今为止,已知在靶基因启动子上调节转录活性是 GLI1 致癌功能的唯一分子事件。在这里,我们提供的证据表明,GLI1 通过调节 SMARCA2(SWI/SNF 相关的,基质相关的,肌动蛋白依赖性的染色质调节剂,亚家族 A,成员 2)到这些元件的募集来控制远端调节区域的染色质可及性。我们证明 SMARCA2 与 GLI1 内源性相互作用并增强其转录活性。映射实验表明,GLI1 的 C 端转录激活结构域和 SMARCA2 的中心结构域,包括其 ATP 酶基序,是这种相互作用所必需的。有趣的是,与 SMARCA2 相似,GLI1 的过表达增加了染色质可及性,微球菌核酸酶测定的结果表明了这一点。此外,GLI1 敲低后进行转座酶可及染色质测序(ATAC-seq)的测定结果支持了这些发现,揭示了 GLI1 调节几个位于基因启动子远端的染色质区域的可及性。整合的 RNA-seq 和 ATAC-seq 数据分析确定了一组位于这些调节染色质位点附近的差异表达基因。最后,我们使用 GLI1 调节的基因()作为模型,证明了 GLI1 和 SMARCA2 共同占据一个远端染色质峰,并且 SMARCA2 对该 HHIP 推定增强子的募集需要完整的 GLI1。这些发现深入了解了 GLI1 如何在癌细胞中控制基因表达,并可能为靶向这种致癌转录因子来管理恶性肿瘤的方法提供信息。