Telomere-binding proteins Taz1 and Rap1 regulate DSB repair and suppress gross chromosomal rearrangements in fission yeast
Telomere-binding proteins Taz1 and Rap1 regulate DSB repair and suppress gross chromosomal rearrangements in fission yeast
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DOI：
10.1371/journal.pgen.1008335
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发表时间：
2019-08-01
期刊：
影响因子：
4.5
通讯作者：
Ishikawa, Fuyuki
中科院分区：
文献类型：
--
作者：
Irie, Hiroyuki;Yamamoto, Io;Ishikawa, Fuyuki
基因组重排（总染色体重排，GCR）威胁基因组的完整性，并导致细胞死亡或肿瘤形成。在线性染色体的末端，一种称为shelterin的端粒结合蛋白复合物通过防止染色体端到端融合和调节端粒长度稳态来确保染色体稳定。因此，shelterin介导的端粒功能在抑制GCR形成中起关键作用。然而，目前还不清楚是否shelterin蛋白发挥任何直接的作用，在非端粒区抑制GCR。在这里，我们已经建立了一个GCR测定的第一次在裂变酵母和测量GCR率在各种突变体。我们发现，缺乏shelterin组件Taz 1或Rap 1（哺乳动物TRF 1/2或RAP 1同源物，分别）的裂变酵母细胞表现出更高的GCR率相比，野生型，积累大的染色体缺失。Rap 1的基因解剖揭示了Rap 1通过两个独立的途径抑制GCR。N-末端BRCT结构域促进忠实的DSB修复，由I-SceI介导的DSB诱导实验确定;此外，与Poz 1介导的中央Poz 1结合结构域调节端粒酶对DSB的可及性，导致从头端粒添加的抑制。我们的数据突出了shelterin组分Taz 1和Rap 1在维持基因组稳定性方面的未被重视的功能，特别是通过防止非端粒GCRs.Author摘要染色体的尖端，端粒，被称为shelterin的端粒结合蛋白复合物结合和保护。大多数以前的研究集中在shelterin的端粒特异性作用，其在基因组维护中的一般作用尚未得到广泛探讨。在这项研究中，我们首先建立了一个测定裂变酵母中总染色体重排（GCR）的细胞分裂自发形成率的方法。我们发现，GCR率升高的突变体缺陷的shelterin组件Taz 1或Rap 1。详细的遗传学实验意外地揭示了Taz 1和Rap 1在修复DNA双链断裂（DSB）和抑制非端粒区域的GCR中具有新的作用。鉴于shelterin组分在裂变酵母和人类之间是保守的，未来的研究有必要测试shelterin功能障碍是否会导致全基因组GCR，这在癌症中经常观察到。
Genomic rearrangements (gross chromosomal rearrangements, GCRs) threatens genome integrity and cause cell death or tumor formation. At the terminus of linear chromosomes, a telomere-binding protein complex, called shelterin, ensures chromosome stability by preventing chromosome end-to-end fusions and regulating telomere length homeostasis. As such, shelterin-mediated telomere functions play a pivotal role in suppressing GCR formation. However, it remains unclear whether the shelterin proteins play any direct role in inhibiting GCR at non-telomeric regions. Here, we have established a GCR assay for the first time in fission yeast and measured GCR rates in various mutants. We found that fission yeast cells lacking shelterin components Taz1 or Rap1 (mammalian TRF1/2 or RAP1 homologues, respectively) showed higher GCR rates compared to wild-type, accumulating large chromosome deletions. Genetic dissection of Rap1 revealed that Rap1 contributes to inhibiting GCRs via two independent pathways. The N-terminal BRCT-domain promotes faithful DSB repair, as determined by I-SceI-mediated DSB-induction experiments; moreover, association with Poz1 mediated by the central Poz1-binding domain regulates telomerase accessibility to DSBs, leading to suppression of de novo telomere additions. Our data highlight unappreciated functions of the shelterin components Taz1 and Rap1 in maintaining genome stability, specifically by preventing non-telomeric GCRs.Author summary Tips of chromosomes, telomeres, are bound and protected by a telomere-binding protein complex called shelterin. Most previous studies focused on shelterin's telomere-specific role, and its general role in genome maintenance has not been explored extensively. In this study, we first set up an assay measuring the spontaneous formation rate per cell division of gross chromosomal rearrangements (GCRs) in fission yeast. We found that the rate of GCRs is elevated in mutants defective for shelterin components Taz1 or Rap1. Detailed genetic experiments revealed unexpectedly that Taz1 and Rap1 have a novel role in repairing DNA double-strand breaks (DSBs) and suppressing GCRs at non-telomeric regions. Given that shelterin components are conserved between fission yeast and humans, future studies are warranted to test whether shelterin dysfunction leads to genome-wide GCRs, which are frequently observed in cancers.