The annealing helicase SMARCAL1 maintains genome integrity at stalled replication forks
The annealing helicase SMARCAL1 maintains genome integrity at stalled replication forks
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DOI：
10.1101/gad.1839909
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发表时间：
2009-10-15
影响因子：
10.5
通讯作者：
Cortez, David
中科院分区：
文献类型：
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作者：
Bansbach, Carol E.;Betous, Remy;Cortez, David
SMARCAL1(HARP)突变导致Schimke免疫性骨质疏松症(SIOD)。这种疾病的发病机制尚不清楚。通过功能基因组筛选，我们鉴定SMARCAL1为基因组维持蛋白。在没有任何遗传毒性因素的情况下，SMARCAL1的沉默和过表达导致了S期DNA损伤反应的激活。SMARCAL1含有一个复制蛋白A(RPA)结合基序，与复制应激反应蛋白TIPIN(时间相互作用蛋白)中发现的基序相似，这对靶向SMARCAL1到停滞的复制叉子是必要的也是充分的。RPA结合是SMARCAL1细胞功能的关键，但在体外，这并不是SMARCAL1解旋酶活性所必需的。SIOD相关的SMARCAL1突变体未能阻止复制相关的DNA损伤在内源性SMARCAL1被沉默的细胞中积累。共济失调-毛细血管扩张突变(ATM)、ATM与Rad3相关(ATR)和DNA依赖蛋白激酶(DNA-PK)使SMARCAL1磷酸化以响应复制压力。SMARCAL1活性的丧失会导致RPA在染色质上的负载量增加，并在短暂的复制应激下持续的RPA磷酸化。此外，SMARCAL1缺陷细胞对复制应激剂高度敏感。因此，SMARCAL1是一种复制应激反应蛋白，SIOD的多效性表型至少部分是由于DNA复制过程中基因组维护的缺陷。
Mutations in SMARCAL1 (HARP) cause Schimke immunoosseous dysplasia (SIOD). The mechanistic basis for this disease is unknown. Using functional genomic screens, we identified SMARCAL1 as a genome maintenance protein. Silencing and overexpression of SMARCAL1 leads to activation of the DNA damage response during S phase in the absence of any genotoxic agent. SMARCAL1 contains a Replication protein A (RPA)-binding motif similar to that found in the replication stress response protein TIPIN (Timeless-Interacting Protein), which is both necessary and sufficient to target SMARCAL1 to stalled replication forks. RPA binding is critical for the cellular function of SMARCAL1; however, it is not necessary for the annealing helicase activity of SMARCAL1 in vitro. An SIOD-associated SMARCAL1 mutant fails to prevent replication-associated DNA damage from accumulating in cells in which endogenous SMARCAL1 is silenced. Ataxia-telangiectasia mutated (ATM), ATM and Rad3-related (ATR), and DNA-dependent protein kinase (DNA-PK) phosphorylate SMARCAL1 in response to replication stress. Loss of SMARCAL1 activity causes increased RPA loading onto chromatin and persistent RPA phosphorylation after a transient exposure to replication stress. Furthermore, SMARCAL1-deficient cells are hypersensitive to replication stress agents. Thus, SMARCAL1 is a replication stress response protein, and the pleiotropic phenotypes of SIOD are at least partly due to defects in genome maintenance during DNA replication.