Subtelomeres are the regions at chromosome ends, immediately adjacent to the terminal telomeric repeats. The majority of human subtelomeres are CpG-rich in their distal two kilobases, and are methylated during early embryonic development by the de novo DNA methyltransferase DNMT3B. The biological relevance of subtelomeric DNA methylation is highlighted by the presence of promoters for the long non-coding TERRA transcripts in these CpG-rich regions. Indeed, deviant subtelomeric methylation has been linked with abnormal telomeric phenotypes, as most strikingly found in ICF syndrome. Here we review recent studies that explore new aspects of subtelomeric methylation regulation and demonstrate the significance of maintaining proper DNA methylation at the extreme distal human subtelomeric regions.

中文翻译：

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人类亚端粒DNA甲基化：调控和端粒功能中的作用。

亚端粒是染色体末端的区域，紧邻末端端粒重复序列。大多数人类亚端粒在其远端2个碱基处富含CpG，并且在早期胚胎发育过程中被从头DNA甲基转移酶DNMT3B甲基化。在这些富含CpG的区域中，长非编码TERRA转录子存在启动子，突显了亚端粒DNA甲基化的生物学相关性。实际上，异常变异的亚端粒甲基化与异常的端粒表型有关，这在ICF综合征中最为明显。在这里，我们回顾了最近的研究，这些研究探索了亚端粒甲基化调控的新方面，并证明了在极端远侧人类亚端粒区域维持适当的DNA甲基化的重要性。