SLFN11 promotes stalled fork degradation that underlies the phenotype in Fanconi anemia cells
SLFN11 promotes stalled fork degradation that underlies the phenotype in Fanconi anemia cells
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DOI：
10.1182/blood.2019003782
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发表时间：
2021-01-21
期刊：
影响因子：
20.3
通讯作者：
Takata, Minoru
中科院分区：
文献类型：
--
作者：
Okamoto, Yusuke;Abe, Masako;Takata, Minoru
范可尼贫血（FA）是一种遗传性疾病，由22个FA基因中的任何一个突变引起。该疾病的特征在于对丝裂霉素C（MMC）等链间交联（ICL）诱导剂的超敏反应。除了促进ICL修复，FA蛋白如RAD 51、BRCA 2或FANCD 2保护停滞的复制叉在复制应激期间免于溶核降解，这可能对FA病理生理学产生深远影响。最近的研究表明，癌细胞中假定的DNA/RNA解旋酶SLFN 11的表达与化疗治疗的细胞死亡相关。然而，SLFN 11介导的DNA损伤敏感性的潜在机制仍不清楚。由于SLFN 11在造血干细胞中表达较高，我们假设SLFN 11缺失可能会改善FA细胞的表型。在这里，我们报告说，在FA患者来源的FANCD 2缺陷型PD 20细胞系中，SLFN 11敲低可改善ICL诱导剂治疗后的细胞存活率。FANCD 2（-/-）SLFN 11（-/-）HAP 1细胞也显示出表型拯救，包括与FANCD 2（-/-）细胞相比MMC诱导的染色体断裂水平降低。重要的是，我们发现SLFN 11促进FANCD 2（-/-）细胞中广泛的叉降解。降解过程由核酸酶MRE 11或DNA 2介导，并取决于SLFN 11 ATP酶活性。这一观察结果伴随着在停滞的叉处增加的RAD 51结合，这与RAD 51拮抗核酸酶募集和随后的叉降解的作用一致。SLFN 11的抑制甚至在野生型细胞中保护新生DNA束。我们的结论是SLFN 11不稳定停滞的复制叉，这种功能可能有助于在FA的造血干细胞的磨损。
Fanconi anemia (FA) is a hereditary disorder caused by mutations in any 1 of 22 FA genes. The disease is characterized by hypersensitivity to interstrand crosslink (ICL) inducers such as mitomycin C (MMC). In addition to promoting ICL repair, FA proteins such as RAD51, BRCA2, or FANCD2 protect stalled replication forks from nucleolytic degradation during replication stress, which may have a profound impact on FA pathophysiology. Recent studies showed that expression of the putative DNA/RNA helicase SLFN11 in cancer cells correlates with cell death on chemotherapeutic treatment. However, the underlying mechanisms of SLFN11-mediated DNA damage sensitivity remain unclear. Because SLFN11 expression is high in hematopoietic stem cells, we hypothesized that SLFN11 depletion might ameliorate the phenotypes of FA cells. Here we report that SLFN11 knockdown in the FA patient-derived FANCD2-deficient PD20 cell line improved cell survival on treatment with ICL inducers. FANCD2(-/-)SLFN11(-/-) HAP1 cells also displayed phenotypic rescue, including reduced levels of MMC-induced chromosome breakage compared with FANCD2(-/-) cells. Importantly, we found that SLFN11 promotes extensive fork degradation in FANCD2(-/-) cells. The degradation process is mediated by the nucleases MRE11 or DNA2 and depends on the SLFN11 ATPase activity. This observation was accompanied by an increased RAD51 binding at stalled forks, consistent with the role of RAD51 antagonizing nuclease recruitment and subsequent fork degradation. Suppression of SLFN11 protects nascent DNA tracts even in wild-type cells. We conclude that SLFN11 destabilizes stalled replication forks, and this function may contribute to the attrition of hematopoietic stem cells in FA.