Telomere binding protein Stn1 forms the CST (Cdc13/CTC1-STN1-TEN1) complex in budding yeast and mammals. Likewise, fission yeast Stn1 and Ten1 form a complex indispensable for telomere protection. We have previously reported that stn1-1, a high-temperature sensitive mutant, rapidly loses telomere DNA at the restrictive temperature due to frequent failure of replication fork progression at telomeres and subtelomeres, both containing repetitive sequences. It is unclear, however, whether Stn1 is required for maintaining other repetitive DNAs such as ribosomal DNA. In this study, we have demonstrated that stn1-1 cells, even when grown at the permissive temperature, exhibited dynamic rearrangements in the telomere-proximal regions of subtelomere and ribosomal DNA repeats. Furthermore, Rad52 and γH2A accumulation was observed at ribosomal DNA repeats in the stn1-1 mutant. The phenotypes exhibited by the stn1-1 allele were largely suppressed in the absence of Reb1, a replication fork barrier-forming protein, suggesting that Stn1 is involved in the maintenance of the arrested replication forks. Collectively, we propose that Stn1 maintains the stability of repetitive DNAs at subtelomeres and rDNA regions.

中文翻译：

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裂变酵母 Stn1 维持亚端粒和核糖体 DNA 区域重复 DNA 的稳定性

端粒结合蛋白 Stn1 在出芽酵母和哺乳动物中形成 CST (Cdc13/CTC1-STN1-TEN1) 复合物。同样，裂变酵母 Stn1 和 Ten1 形成了对端粒保护必不可少的复合物。我们之前曾报道过 stn1-1 是一种高温敏感突变体，由于端粒和亚端粒的复制叉进程经常失败，因此在限制温度下会迅速失去端粒 DNA，两者都包含重复序列。然而，尚不清楚 Stn1 是否是维持其他重复 DNA（如核糖体 DNA）所必需的。在这项研究中，我们已经证明 stn1-1 细胞，即使在允许的温度下生长，在亚端粒和核糖体 DNA 重复序列的端粒近端区域也表现出动态重排。此外，在 stn1-1 突变体的核糖体 DNA 重复序列中观察到 Rad52 和 γH2A 积累。stn1-1 等位基因表现出的表型在没有 Reb1（一种复制叉屏障形成蛋白）的情况下受到很大抑制，这表明 Stn1 参与了停滞复制叉的维持。总的来说，我们建议 Stn1 维持亚端粒和 rDNA 区域重复 DNA 的稳定性。