Sikder Sweta, Baek Songjoon, Dalal Yamini, Arunkumar Ganesan
Chromosome Structure and Epigenetic Mechanisms Unit, Laboratory of Receptor Biology and Gene Expression, Center for Cancer Research, NCI, NIH, Bethesda, MD 20892, USA.
LncRNA, Epigenetics, and Genome Organization Laboratory, Department of Cell Biology and Physiology, School of Medicine, University of New Mexico, Albuquerque 87131, NM, USA.
bioRxiv. 2025 May 19:2025.05.15.654293. doi: 10.1101/2025.05.15.654293.
Maintaining genome integrity is crucial for the proper functioning and development of organisms. One intriguing aspect of genome integrity is the formation and function of neocentromeres at non-centromeric sites. CENP-A, a centromere-specific protein, is essential for centromere identification and function. However, in many cancers, CENP-A is often found to be ectopically misplaced when overexpressed. Moreover, CENP-A deposition at the centromere depends on the transcription of centromeric non-coding RNAs. Consequently, ectopic CENP-A is found at transcriptionally active and frequent breakpoint regions. To further explore ectopic CENP-A localization, we previously engineered a stable ectopic CENP-A site on a naïve chromosome by overexpressing a non-centromeric oncogenic lncRNA, PCAT2, which was capable of recruiting CENP-A to its transcription site. In this work, we tracked cells carrying this stable transgene to understand the longevity of the induced ectopic CENP-A site at the chromosome that harbors it. Our findings revealed that the induced epigenetic memory was eventually lost due to the suppression of the transgene through competing epigenetic silencing mechanisms. This epigenetic restoration naturally reversed the ectopic CENP-A level to its previous levels at the engineered site. These data suggest that cells may have evolved failsafe mechanisms to prevent neocentromere formation at ectopic sites by suppressing transcription, unless otherwise favored by selection involving multiple components.
维持基因组完整性对于生物体的正常功能和发育至关重要。基因组完整性的一个有趣方面是在非着丝粒位点上新着丝粒的形成和功能。着丝粒特异性蛋白CENP - A对于着丝粒的识别和功能至关重要。然而，在许多癌症中，CENP - A在过表达时常常被异位错置。此外，CENP - A在着丝粒处的沉积取决于着丝粒非编码RNA的转录。因此，在转录活跃且频繁出现断点的区域发现了异位的CENP - A。为了进一步探索异位CENP - A的定位，我们之前通过过表达一种非着丝粒致癌长链非编码RNA（lncRNA）PCAT2，在一条原始染色体上构建了一个稳定的异位CENP - A位点，该lncRNA能够将CENP - A招募到其转录位点。在这项工作中，我们追踪携带这种稳定转基因的细胞，以了解在含有该转基因的染色体上诱导产生的异位CENP - A位点的持久性。我们的研究结果表明，由于通过竞争性表观遗传沉默机制抑制了转基因，诱导产生的表观遗传记忆最终丧失。这种表观遗传恢复自然地将异位CENP - A水平恢复到工程位点之前的水平。这些数据表明，细胞可能已经进化出了故障安全机制，通过抑制转录来防止在异位位点形成新着丝粒，除非受到涉及多个组件的选择的青睐。
