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 DNAtracts even in wild-type cells.Weconclude that SLFN11 destabilizes stalled replication forks, and this function may contribute to the attrition of hematopoietic stem cells in FA.
Bibliographical noteFunding Information:
This work was supported by Japan Society for the Promotion of Science (JSPS) Kagaku Kenkyuhi Hojokin (KAKENHI) Grants, Takeda Science Foundation, Uehara Memorial Foundation, Astellas Foundation for Research on Metabolic Disorders, and Kyoto University Research Fund (Core Stage Back-Up). A.-K.B. was supported by National Institutes of Health grants 5R01 GM074917 and 1R01 GM134681 and C.B.R. is a trainee on Cancer Biology Training grant T32 CA009138 and a Scholar of the Achievement Rewards for College Scientists (ARCS) Foundation. Radiation Biology Center, Graduate School of Biostudies, Kyoto University, is a joint usage research center certified by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.
© 2021 by The American Society of Hematology.
PubMed: MeSH publication types
- Journal Article
- Research Support, N.I.H., Extramural
- Research Support, Non-U.S. Gov't