Hsu P-Y, Hsu H-K, Hsiao T-H, Ye Z, Wang E, Profit A L, Jatoi I, Chen Y, Kirma N B, Jin V X, Sharp Z D, Huang T H-M
Department of Molecular Medicine, Institute of Biotechnology, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
Greehey Children's Cancer Research Institute, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
Oncogene. 2016 May 5;35(18):2379-89. doi: 10.1038/onc.2015.298. Epub 2015 Aug 24.
Recruitment of transcription machinery to target promoters for aberrant gene expression has been well studied, but underlying control directed by distant-acting enhancers remains unclear in cancer development. Our previous study demonstrated that distant estrogen response elements (DEREs) located on chromosome 20q13 are frequently amplified and translocated to other chromosomes in ERα-positive breast cancer cells. In this study, we used three-dimensional interphase fluorescence in situ hybridization to decipher spatiotemporal gathering of multiple DEREs in the nucleus. Upon estrogen stimulation, scattered 20q13 DEREs were mobilized to form regulatory depots for synchronized gene expression of target loci. A chromosome conformation capture assay coupled with chromatin immunoprecipitation further uncovered that ERα-bound regulatory depots are tethered to heterochromatin protein 1 (HP1) for coordinated chromatin movement and histone modifications of target loci, resulting in transcription repression. Neutralizing HP1 function dysregulated the formation of DERE-involved regulatory depots and transcription inactivation of candidate tumor-suppressor genes. Deletion of amplified DEREs using the CRISPR/Cas9 genomic-editing system profoundly altered transcriptional profiles of proliferation-associated signaling networks, resulting in reduction of cancer cell growth. These findings reveal a formerly uncharacterized feature wherein multiple copies of the amplicon congregate as transcriptional units in the nucleus for synchronous regulation of function-related loci in tumorigenesis. Disruption of their assembly can be a new strategy for treating breast cancers and other malignancies.
转录机制募集到异常基因表达的靶启动子上已得到充分研究，但在癌症发展过程中，由远距离作用增强子介导的潜在调控仍不清楚。我们之前的研究表明，位于20号染色体q13区域的远距离雌激素反应元件（DEREs）在雌激素受体α（ERα）阳性乳腺癌细胞中经常发生扩增并易位到其他染色体上。在本研究中，我们使用三维间期荧光原位杂交技术来解析多个DEREs在细胞核中的时空聚集情况。雌激素刺激后，分散的20q13 DEREs被动员起来形成调控位点，用于靶基因座的同步基因表达。结合染色质免疫沉淀的染色体构象捕获分析进一步发现，与ERα结合的调控位点与异染色质蛋白1（HP1）相连，以协调靶基因座的染色质运动和组蛋白修饰，从而导致转录抑制。中和HP1功能会使涉及DEREs的调控位点形成失调，并使候选肿瘤抑制基因的转录失活。使用CRISPR/Cas9基因组编辑系统删除扩增的DEREs会深刻改变增殖相关信号网络的转录谱，从而导致癌细胞生长减少。这些发现揭示了一个以前未被描述的特征，即扩增子的多个拷贝在细胞核中作为转录单元聚集在一起，用于在肿瘤发生过程中对功能相关基因座进行同步调控。破坏它们的组装可能是治疗乳腺癌和其他恶性肿瘤的一种新策略。
