Cancer and aging, two distinct processes of cell development, are two major problems threatening our human health and life in current days. Epigenetic studies, especially DNA methylation, have been intensively investigated on them over the years, though a lot of unanswered issues remain. In the human genome, rDNA is a highly conserved tandem repeat family playing critical roles in protein synthesis, genome stability and integrity, etc. More importantly, rDNA is the significant target of DNA methylation, and a potential association between rDNA methylation and cancer and aging has emerged recently. However, whether there is a general trend that rDNA methylation is associated with cancer and aging remains an open issue. In this study, the involvement of rDNA methylation in a series of records of cancer and aging was investigated and summarized, upon which perspectives about rDNA methylation in cancer and aging were proposed. The results showed that rDNA methylation in most cancer cases displayed a consistent pattern with hypermethylation in the coding region but with hypomethylation in the promoter region, which likely facilitates the proliferation and metastasis of cancerous cells. Distinctively, both the coding and promoter regions of rDNA become increasingly methylated during the process of aging, indicating the decline of rDNA activity. The finding of rDNA methylation also implies its potential application as an epigenetic biomarker in the diagnosis of cancer and aging. This work will shed light on our understanding of the pathogenesis, diagnosis, and treatment of cancer and aging from the perspective of rDNA methylation.

中文翻译：

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45S核糖体DNA（rDNA）的甲基化与人类癌症和衰老相关

癌症和衰老是细胞发育的两个不同过程，是当今威胁人类健康和生命的两个主要问题。多年来，对表观遗传学的研究，尤其是DNA甲基化，已经进行了深入研究，尽管仍有许多未解决的问题。在人类基因组中，rDNA是高度保守的串联重复家族，在蛋白质合成，基因组稳定性和完整性等方面起着至关重要的作用。更重要的是，rDNA是DNA甲基化的重要目标，并且是rDNA甲基化与癌症和衰老之间的潜在关联。最近出现了。但是，是否存在rDNA甲基化与癌症和衰老相关的普遍趋势仍然是一个未解决的问题。在这项研究中，对rDNA甲基化在一系列癌症和衰老记录中的参与进行了调查和总结，提出了关于癌症和衰老中rDNA甲基化的观点。结果表明，在大多数癌症病例中，rDNA甲基化表现出一致的模式，在编码区域具有高甲基化，而在启动子区域具有低甲基化，这可能促进了癌细胞的增殖和转移。尤其是，rDNA的编码区和启动子区在衰老过程中都变得越来越甲基化，表明rDNA活性下降。rDNA甲基化的发现也暗示了其作为表观遗传生物标志物在癌症和衰老诊断中的潜在应用。这项工作将从rDNA甲基化的角度阐明我们对癌症和衰老的发病机理，诊断和治疗的理解。