Rtt105 functions as a chaperone for replication protein A to preserve genome stability
Rtt105 functions as a chaperone for replication protein A to preserve genome stability
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DOI：
10.15252/embj.201899154
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发表时间：
2018-09-03
期刊：
影响因子：
11.4
通讯作者：
Li, Qing
中科院分区：
文献类型：
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作者：
Li, Shuqi;Xu, Zhiyun;Li, Qing
在DNA复制过程中，模板链的形成需要产生单链DNA(SsDNA)。复制蛋白A(Replica Protein A，RPA)是一种单链DNA结合蛋白，在真核细胞的复制叉处保护单链DNA是必不可少的。虽然在表征RPA-ssDNA复合体的作用方面已经取得了重大进展，但RPA是如何加载在复制叉处的仍然缺乏研究。在这里，我们证明了Ty1转座105(Rtt105)的酿酒酵母蛋白调节器与RPA结合，并帮助将其装载在复制叉处。缺乏Rtt105的细胞表现出复制叉处RPA负载的急剧减少，复制应激下DNA合成的损害，以及基因组不稳定性的增加。从机制上讲，我们证明了Rtt105介导了RPA-Importin的相互作用，并在体外直接促进了RPA与ssDNA的结合，但在最终的RPA-ssDNA复合体中不存在。单分子研究表明，Rtt105影响RPA与单链DNA的结合方式。这些结果支持一种模型，在该模型中，Rtt105作为RPA伴侣，护送RPA到细胞核，并促进其在复制叉处装载到ssDNA上。
Generation of single-stranded DNA (ssDNA) is required for the template strand formation during DNA replication. Replication Protein A (RPA) is an ssDNA-binding protein essential for protecting ssDNA at replication forks in eukaryotic cells. While significant progress has been made in characterizing the role of the RPA-ssDNA complex, how RPA is loaded at replication forks remains poorly explored. Here, we show that the Saccharomyces cerevisiae protein regulator of Ty1 transposition 105 (Rtt105) binds RPA and helps load it at replication forks. Cells lacking Rtt105 exhibit a dramatic reduction in RPA loading at replication forks, compromised DNA synthesis under replication stress, and increased genome instability. Mechanistically, we show that Rtt105 mediates the RPA-importin interaction and also promotes RPA binding to ssDNA directly in vitro, but is not present in the final RPA-ssDNA complex. Single-molecule studies reveal that Rtt105 affects the binding mode of RPA to ssDNA. These results support a model in which Rtt105 functions as an RPA chaperone that escorts RPA to the nucleus and facilitates its loading onto ssDNA at replication forks.