Yadav Rajesh K, Matsuda Atsushi, Lowe Brandon R, Hiraoka Yasushi, Partridge Janet F
Department of Biochemistry, All India Institute of Medical Sciences Patna, Patna PIN-801507, Bihar, India.
Advanced ICT Research Institute Kobe, National Institute of Information and Communications Technology, Kobe 651-2492, Japan.
Microorganisms. 2021 Sep 17;9(9):1977. doi: 10.3390/microorganisms9091977.
Telomeres play important roles in safeguarding the genome. The specialized repressive chromatin that assembles at telomeres and subtelomeric domains is key to this protective role. However, in many organisms, the repetitive nature of telomeric and subtelomeric sequences has hindered research efforts. The fission yeast has provided an important model system for dissection of chromatin biology due to the relative ease of genetic manipulation and strong conservation of important regulatory proteins with higher eukaryotes. Telomeres and the telomere-binding shelterin complex are highly conserved with mammals, as is the assembly of constitutive heterochromatin at subtelomeres. In this review, we seek to summarize recent work detailing the assembly of distinct chromatin structures within subtelomeric domains in fission yeast. These include the heterochromatic SH subtelomeric domains, the telomere-associated sequences (TAS), and ST chromatin domains that assemble highly condensed chromatin clusters called knobs. Specifically, we review new insights into the sequence of subtelomeric domains, the distinct types of chromatin that assemble on these sequences and how histone H3 K36 modifications influence these chromatin structures. We address the interplay between the subdomains of chromatin structure and how subtelomeric chromatin is influenced by both the telomere-bound shelterin complexes and by euchromatic chromatin regulators internal to the subtelomeric domain. Finally, we demonstrate that telomere clustering, which is mediated via the condensed ST chromatin knob domains, does not depend on knob assembly within these domains but on Set2, which mediates H3K36 methylation.
端粒在保护基因组方面发挥着重要作用。在端粒和亚端粒区域组装的特殊抑制性染色质是这一保护作用的关键。然而，在许多生物体中，端粒和亚端粒序列的重复性阻碍了研究工作。由于遗传操作相对容易且与高等真核生物在重要调控蛋白上具有高度保守性，裂殖酵母为剖析染色质生物学提供了一个重要的模型系统。端粒和端粒结合的保护素复合体与哺乳动物高度保守，亚端粒处组成型异染色质的组装也是如此。在本综述中，我们试图总结最近的工作，详细阐述裂殖酵母亚端粒区域内不同染色质结构的组装。这些结构包括异染色质的SH亚端粒区域、端粒相关序列（TAS）以及组装称为小节的高度浓缩染色质簇的ST染色质区域。具体而言，我们综述了关于亚端粒区域序列的新见解、在这些序列上组装的不同类型染色质以及组蛋白H3 K36修饰如何影响这些染色质结构。我们探讨了染色质结构亚域之间的相互作用，以及亚端粒染色质如何受到端粒结合的保护素复合体和亚端粒区域内常染色质调节因子的影响。最后，我们证明通过浓缩的ST染色质小节结构域介导的端粒聚集并不依赖于这些结构域内小节的组装，而是依赖于介导H3K36甲基化的Set2。
