Roles of Specialized Chromatin and DNA Structures at Subtelomeres in Schizosaccharomyces pombe

Eukaryotes have linear chromosomes with domains called telomeres at both ends. The telomere DNA consists of a simple tandem repeat sequence, and multiple telomere-binding proteins including the shelterin complex maintain chromosome-end structures and regulate various biological reactions, such as protection of chromosome ends and control of telomere DNA length. On the other hand, subtelomeres, which are located adjacent to telomeres, contain a complex mosaic of multiple common segmental sequences and a variety of gene sequences. This review focused on roles of the subtelomeric chromatin and DNA structures in the fission yeast Schizosaccharomyces pombe. The fission yeast subtelomeres form three distinct chromatin structures; one is the shelterin complex, which is localized not only at the telomeres but also at the telomere-proximal regions of subtelomeres to form transcriptionally repressive chromatin structures. The others are heterochromatin and knob, which have repressive effects in gene expression, but the subtelomeres are equipped with a mechanism that prevents these condensed chromatin structures from invading adjacent euchromatin regions. On the other hand, recombination reactions within or near subtelomeric sequences allow chromosomes to be circularized, enabling cells to survive in telomere shortening. Furthermore, DNA structures of the subtelomeres are more variable than other chromosomal regions, which may have contributed to biological diversity and evolution while changing gene expression and chromatin structures.

Automated summary

Eukaryotes have linear chromosomes with telomeres at both ends, which consist of simple tandem repeat DNA sequences and telomere-binding proteins. This review focuses on the subtelomeric chromatin and DNA structures in the fission yeast Schizosaccharomyces pombe. The subtelomeres form distinct chromatin structures, including the shelterin complex, heterochromatin, and knob, which play roles in gene expression regulation and preventing invasion of condensed chromatin structures. Recombination reactions within or near subtelomeric sequences enable chromosome circularization and survival in telomere shortening. The variable DNA structures of subtelomeres contribute to biological diversity and evolution.