BRCA1 Regulation of Fanconi Anemia Proteins in DNA Damage Repair

Fanconi anemia (FA) is a disease of genomic instability and cancer. In addition to DNA damage repair, FA pathway proteins are now known to be critical for maintaining faithful chromosome segregation during mitosis. While impaired DNA damage repair has been studied extensively in FA-associated carcinogenesis in vivo, the oncogenic contribution of mitotic abnormalities secondary to FA pathway deficiency remains incompletely understood. To examine the role of mitotic dysregulation in FA pathway deficient malignancies, we genetically exacerbated the baseline mitotic defect in Fancc-/- mice by introducing heterozygosity of the key spindle assembly checkpoint regulator Mad2. Fancc-/-;Mad2+/- mice were viable, but died from acute myeloid leukemia (AML), thus recapitulating the high risk of myeloid malignancies in FA patients better than Fancc-/-mice. We utilized hematopoietic stem cell transplantation to propagate Fancc-/-; Mad2+/- AML in irradiated healthy mice to model FANCC-deficient AMLs arising in the non-FA population. Compared to cells from Fancc-/- mice, those from Fancc-/-;Mad2+/- mice demonstrated an increase in mitotic errors but equivalent DNA cross-linker hypersensitivity, indicating that the cancer phenotype of Fancc-/-;Mad2+/- mice results from error-prone cell division and not exacerbation of the DNA damage repair defect. We found that FANCC enhances targeting of endogenous MAD2 to prometaphase kinetochores, suggesting a mechanism for how FANCC-dependent regulation of the spindle assembly checkpoint prevents chromosome mis-segregation. Whole-exome sequencing revealed similarities between human FA-associated myelodysplastic syndrome (MDS)/AML and the AML that developed in Fancc-/-; Mad2+/- mice. Together, these data illuminate the role of mitotic dysregulation in FA-pathway deficient malignancies in vivo, show how FANCC adjusts the spindle assembly checkpoint rheostat by regulating MAD2 kinetochore targeting in cell cycle-dependent manner, and establish two new mouse models for preclinical studies of AML.

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Fanconi Anemia FANCM/FNCM-1 and FANCD2/FCD-2 are required for maintaining histone methylation levels and interact with the histone demethylase LSD1/SPR-5 in C. elegans

10.1101/265876 ◽

2018 ◽

Author(s):

Hyun-Min Kim ◽

Sara E. Beese-Sims ◽

Monica P. Colaiácovo

Keyword(s):

Dna Damage ◽

Fanconi Anemia ◽

Histone Methylation ◽

Dna Damage Repair ◽

Replication Stress ◽

Histone Demethylase ◽

Histone Demethylases ◽

Checkpoint Activation ◽

C Elegans ◽

Damage Repair

ABSTRACTThe histone demethylase LSD1 was originally discovered as removing methyl groups from di- and monomethylated histone H3 lysine 4 (H3K4me2/1), and several studies suggest it plays roles in meiosis as well as epigenetic sterility given that in its absence there is evidence of a progressive accumulation of H3K4me2 through generations. In addition to transgenerational sterility, growing evidence for the importance of histone methylation in the regulation of DNA damage repair has attracted more attention to the field in recent years. However, we are still far from understanding the mechanisms by which histone methylation is involved in DNA damage repair and only a few studies have been focused on the roles of histone demethylases in germline maintenance. Here, we show that the histone demethylase LSD1/CeSPR-5 is interacting with the Fanconi Anemia (FA) protein FANCM/CeFNCM-1 based on biochemical, cytological and genetic analyses. LSD1/CeSPR-5 is required for replication stress-induced S-phase checkpoint activation and its absence suppresses the embryonic lethality and larval arrest observed in fncm-1 mutants. FANCM/CeFNCM-1 re-localizes upon hydroxyurea exposure and co-localizes with FANCD2/CeFCD-2 and LSD1/CeSPR-5 suggesting coordination between this histone demethylase and FA components to resolve replication stress. Surprisingly, the FA pathway is required for H3K4me2 maintenance regardless of the presence of replication stress. Our study reveals a connection between Fanconi Anemia and epigenetic maintenance, therefore providing new mechanistic insight into the regulation of histone methylation in DNA repair.

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An ATR- and BRCA1-Mediated Fanconi Anemia Pathway Is Required for Activating the G2/M Checkpoint and DNA Damage Repair upon Rereplication

Molecular and Cellular Biology ◽

10.1128/mcb.02141-05 ◽

2006 ◽

Vol 26 (12) ◽

pp. 4601-4611 ◽

Cited By ~ 48

Author(s):

Wenge Zhu ◽

Anindya Dutta

Keyword(s):

Cell Cycle ◽

Dna Damage ◽

Fanconi Anemia ◽

Autosomal Recessive ◽

Cancer Susceptibility ◽

Human Cancer ◽

Dna Damage Repair ◽

Human Cancer Cells ◽

Damage Repair ◽

Artificial Induction

ABSTRACT The timely assembly of prereplicative complexes at replication origins is tightly controlled to ensure that genomic DNA is replicated once per cell cycle. The loss of geminin, a DNA replication inhibitor, causes rereplication that activates a G2/M checkpoint in human cancer cells. Fanconi anemia (FA) is an autosomal recessive and X-linked disorder associated with cancer susceptibility. Here we show that rereplication activates the FA pathway both for the activation of a G2/M checkpoint and for repair processes, like recruitment of RAD51. Both ATR and BRCA1 are required to activate the FA pathway. The G2/M checkpoint-mediated arrest of the cell cycle is critical for the prevention of both apoptosis and the accumulation of cells with rereplicated DNA, because the loss of ATR, BRCA1, or FANCA promotes apoptosis and suppresses the accumulation. The accumulation of cells with rereplicated DNA is restored by the artificial induction of a G2-phase arrest even when ATR, BRCA1, or FANCA is absent. Therefore, the ATR- and BRCA1-mediated FA pathway is required for the activation of a G2/M checkpoint and for DNA damage repair in response to the endogenous signal of rereplication. In its absence, the cells rapidly lose viability when faced with rereplication.

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