BRCA1 functions independently of homologous recombination in DNA interstrand crosslink repair
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE35698 | GEO | 2012/09/30
SECONDARY ACCESSION(S): PRJNA152035
REPOSITORIES: GEO
Similar Datasets
Project description:Brca1 is required for DNA repair by homologous recombination (HR) and normal embryonic development. Here we report that deletion of the DNA damage responsefactor 53BP1 overcomes embryonic lethality in Brca1-nullizygous mice, and rescues HR deficiency, as measured by hypersensitivity to PARP (polyADPribose polymerase) inhibition. However, Brca1,53BP1 double-deficient cells are hypersensitive to DNA interstrand crosslinks (ICLs), indicating that BRCA1 has an additional role in DNA cross-link repair that is distinct from HR. Disruption of the non-homologous end-joining (NHEJ) factor, Ku, promotes DNA repair in Brca1-deficient cells; however deletion of either Ku or 53BP1 exacerbates genomic instability in cells lacking FANCD2, a mediator of the Fanconi Anemia pathway for ICL repair. Brca1 therefore has two separate roles in ICL repair, whereas FANCD2 provides a key activity that can not be bypassed by ablation of 53BP1 or Ku. B cells were stimulated to undergo class switch recombination in vitro. Chromatin from B cells was harvested 72 hours post-stimulation and used for RPA ChIP to study the extent of resection of DNA DSBs.
2012-09-30 | E-GEOD-35698 | biostudies-arrayexpress
Project description:By covalently linking Watson and Crick strands, DNA interstrand crosslinks (ICLs) are highly toxic lesions that block DNA replication and threaten genome integrity. The Fanconi anemia (FA) pathway orchestrates ICL repair during DNA replication, with ubiquitylated FANCI-FANCD2 (ID2) marking the activation step that triggers incisions on one DNA strand to unhook the ICL. ICL unhooking generates a two-ended double-strand break (DSB) on one of the daughter molecules, while leaving a gap comprising the ICL-adduct on the other. Restoration of the adducted molecule by DNA polymerase zeta-mediated translesion synthesis (TLS) creates a template required for repair of the DSB via homologous recombination (HR), but how these processes are coordinated to ensure faithful ICL repair is not known. Here, we uncover a crucial role for SCAI in promoting ICL repair downstream of ID2 activation. Using Xenopus egg extracts and human cells, we show that SCAI forms a complex with DNA polymerase zeta and localizes to ICLs during DNA replication. SCAI-deficient cells are exquisitely sensitive to ICL-inducing drugs and display principal hallmarks of FA gene inactivation, including broken and radial chromosome accumulation. In the absence of SCAI, DSB intermediates are preferentially re-ligated by illegitimate DNA polymerase theta-dependent microhomology-mediated end-joining (MMEJ). Consistently, the hypersensitivity of SCAI-deficient cells to ICLs can be reverted by suppressing FA pathway activation. Our work establishes SCAI as a critical mediator of ICL resolution via the FA pathway, acting at the interphase of the TLS and HR steps to prevent erroneous repair and chromosomal instability.
2022-02-18 | PXD029409 | Pride
Project description:By covalently linking Watson and Crick strands, DNA interstrand crosslinks (ICLs) are highly toxic lesions that block DNA replication and threaten genome integrity. The Fanconi anemia (FA) pathway orchestrates ICL repair during DNA replication, with ubiquitylated FANCI-FANCD2 (ID2) marking the activation step that triggers incisions on one DNA strand to unhook the ICL. ICL unhooking generates a two-ended double-strand break (DSB) on one of the daughter molecules, while leaving a gap comprising the ICL-adduct on the other. Restoration of the adducted molecule by DNA polymerase zeta-mediated translesion synthesis (TLS) creates a template required for repair of the DSB via homologous recombination (HR), but how these processes are coordinated to ensure faithful ICL repair is not known. Here, we uncover a crucial role for SCAI in promoting ICL repair downstream of ID2 activation. Using Xenopus egg extracts and human cells, we show that SCAI forms a complex with DNA polymerase zeta and localizes to ICLs during DNA replication. SCAI-deficient cells are exquisitely sensitive to ICL-inducing drugs and display principal hallmarks of FA gene inactivation, including broken and radial chromosome accumulation. In the absence of SCAI, DSB intermediates are preferentially re-ligated by illegitimate DNA polymerase theta-dependent microhomology-mediated end-joining (MMEJ). Consistently, the hypersensitivity of SCAI-deficient cells to ICLs can be reverted by suppressing FA pathway activation. Our work establishes SCAI as a critical mediator of ICL resolution via the FA pathway, acting at the interphase of the TLS and HR steps to prevent erroneous repair and chromosomal instability.
2022-02-18 | PXD024280 | Pride
Project description:The 53BP1-RIF1 pathway antagonizes resection of DNA broken ends and confers PARP inhibitor sensitivity on BRCA1-mutated tumors. However, it is unclear how this pathway suppresses initiation of resection. Here, we identify ASF1 as a partner of RIF1 via an interacting manner similar to its interactions with histone chaperones CAF-1 and HIRA. ASF1 is recruited to distal chromatin flanking DNA breaks by 53BP1-RIF1 and promotes non-homologous end joining (NHEJ) using its histone chaperone activity. Epistasis analysis shows that ASF1 acts in the same NHEJ pathway as RIF1, but via a parallel pathway with the shieldin complex, which suppresses resection after initiation. Moreover, defects in end resection and homologous recombination (HR) in BRCA1-deficient cells are largely suppressed by ASF1 deficiency. Mechanistically, ASF1 compacts adjacent chromatin by heterochromatinization to protect broken DNA ends from BRCA1-mediated resection. Taken together, our findings identified a RIF1-ASF1 histone chaperone complex that promotes changes in high-order chromatin structure to stimulate the NHEJ pathway for DSB repair.
2022-02-04 | PXD031311 | Pride
Project description:53BP1 governs a specialized, context-specific branch of the classical non-homologous end joining DNA double-strand break repair pathway. Mice lacking 53bp1 (also known as Trp53bp1) are immunodeficient owing to a complete loss of immunoglobulin class-switch recombination, and reduced fidelity of long-range V(D)J recombination. The 53BP1-dependent pathway is also responsible for pathological joining events at dysfunctional telomeres, and its unrestricted activity in Brca1-deficient cellular and tumour models causes genomic instability and oncogenesis. Cells that lack core non-homologous end joining proteins are profoundly radiosensitive, unlike 53BP1-deficient cells, which suggests that 53BP1 and its co-factors act on specific DNA substrates. Here we show that 53BP1 cooperates with its downstream effector protein REV7 to promote non-homologous end joining during class-switch recombination, but REV7 is not required for 53BP1-dependent V(D)J recombination. We identify shieldin—a four-subunit putative single-stranded DNA-binding complex comprising REV7, c20orf196 (SHLD1), FAM35A (SHLD2) and FLJ26957 (SHLD3)— as the factor that explains this specificity. Shieldin is essential for REV7-dependent DNA end-protection and non-homologous end joining during class-switch recombination, and supports toxic non-homologous end joining in Brca1-deficient cells, yet is dispensable for REV7-dependent interstrand cross-link repair. The 53BP1 pathway therefore comprises distinct double-strand break repair activities within chromatin and single-stranded DNA compartments, which explains both the immunological differences between 53bp1- and Rev7- deficient mice and the context specificity of the pathway.
2018-07-26 | PXD009650 | Pride
Project description:Homologous recombination-mediated DNA repair deficiency (HRD) predisposes to cancer development, but also provides therapeutic opportunities. Here, we identified an HRD gene signature that robustly predicted HRD status. Unexpectedly, concurrent loss of PTEN in BRCA1-deficient cells might extensively rewire the HR repair network and confer resistance to PARP inhibitor, partially through over-expression of TTK. We used the HRD gene signature as a drug discovery tool and found several PARP-inhibitor-synergizing agents through the connectivity map. Thus gene expression profiling can be used to define the functional status of the HR repair network providing prognostic and therapeutic information. Various shRNAs that target genes involved in homologous recombination (HR) were transfected in MCF-10A non-transformed breast cells lines. Stable HR gene knockdown MCF-10A cells were seeded 200000 at 10 cm plate. Cells were harvested after 48 hours culturing and used for gene expression profiling. The shRNAs that target ATM, ATR, CHK1, CHK2, and 53BP1 genes were transfected in MCF-10A non-transformed breast cell line by lentiviral particles and selected stable ATM, ATR, CHK1, CHK2, and 53BP1 knockdown MCF-10A cells. Scrambled control shRNA-transfected and wild type MCF-10A cells were applying as control. All knockdown and control MCF-10A cells were seeded with 2 x 10^5 cells at 10 cm culture plate. Cells were cultured in MCF-10A medium and harvested after 48 hours culturing. mRNA was extracted from collected cells and performing gene expression profiling. Three biological replicates were applied.
2014-01-24 | E-GEOD-54268 | biostudies-arrayexpress
Project description:RIF1 acts downstream of 53BP1 to coordinate DNA double strand break repair pathway choice between non-homologous end joining (NHEJ) and homologous recombination (HR). Here we identified ASF1 as an endogenous RIF1-associated protein. We showed that ASF1 forms complex with RIF1 and regulates RIF1-dependent functions in DNA damage response.
2022-06-09 | PXD027727 | Pride
Project description:DNA double-strand breaks (DSBs) are highly cytotoxic DNA lesions, whose accurate repair by non-homologous end-joining (NHEJ) or homologous recombination (HR) is crucial for genome integrity and is strongly influenced by the local chromatin environment. Here, we identify SCAI (Suppressor of Cancer Cell Invasion) as a 53BP1-interacting chromatin-associated protein that promotes the functionality of several DSB repair pathways in mammalian cells. SCAI undergoes prominent enrichment at DSB sites through dual mechanisms involving 53BP1-dependent recruitment to DSB-surrounding chromatin and 53BP1-independent accumulation at resected DSBs. Cells lacking SCAI display reduced DSB repair capacity, hypersensitivity to DSB-inflicting agents and genome instability. We demonstrate that SCAI is a mediator of 53BP1-dependent repair of heterochromatin-associated DSBs, facilitating ATM kinase signaling at DSBs in repressive chromatin environments. Moreover, we establish an important role of SCAI in meiotic recombination, as SCAI deficiency in mice leads to germ cell loss and subfertility associated with impaired retention of the DMC1 recombinase on meiotic chromosomes. Collectively, our findings uncover SCAI as a physiologically important component of both NHEJ- and HR-mediated pathways that potentiates DSB repair efficiency in specific chromatin contexts.
2016-12-12 | PXD004912 | Pride
Project description:Double-strand break (DSB) repair choice is greatly influenced by the initial processing of DNA ends. 53BP1 limits the formation of recombinogenic single strand DNA (ssDNA) in BRCA1-deficient cells leading to defects in homologous recombination (HR). However, the exact mechanisms by which 53BP1 inhibits DSB resection remain unclear. Previous studies have identified two potential pathways: protection against exonucleases presumably through the Shieldin (SHLD) complex binding to ssDNA, and localized DNA synthesis through the (CTC1-STN1-TEN1) CST and DNA polymerase alpha (Polα) to counteract resection. We present evidence here that 53BP1-mediated exonuclease protection plays a more significant role than CST/Polα synthesis in countering hyper-resection at DSBs in G1 phase. Using a combinatorial approach of END-seq, SAR-seq, and RPA ChIP-seq, we directly assessed the extent of resection, DNA synthesis, and ssDNA, respectively, at AsiSI-induced DSBs. We show that in the presence of 53BP1, Polα-dependent DNA synthesis reduces the fraction of resected DSBs and the resection lengths. However, in the absence of 53BP1, Polα activity is sustained on ssDNA yet does not substantially counter resection. In contrast, Exo1 nuclease activity is essential for hyperresection in the absence of 53BP1. Thus, 53BP1 inhibits resection mainly through end-protection rather than by promoting fill-in.
2021-09-10 | GSE181667 | GEO
Project description:Double-strand break (DSB) repair choice is greatly influenced by the initial processing of DNA ends. 53BP1 limits the formation of recombinogenic single strand DNA (ssDNA) in BRCA1-deficient cells leading to defects in homologous recombination (HR). However, the exact mechanisms by which 53BP1 inhibits DSB resection remain unclear. Previous studies have identified two potential pathways: protection against exonucleases presumably through the Shieldin (SHLD) complex binding to ssDNA, and localized DNA synthesis through the (CTC1-STN1-TEN1) CST and DNA polymerase alpha (Polα) to counteract resection. We present evidence here that 53BP1-mediated exonuclease protection plays a more significant role than CST/Polα synthesis in countering hyper-resection at DSBs in G1 phase. Using a combinatorial approach of END-seq, SAR-seq, and RPA ChIP-seq, we directly assessed the extent of resection, DNA synthesis, and ssDNA, respectively, at AsiSI-induced DSBs. We show that in the presence of 53BP1, Polα-dependent DNA synthesis reduces the fraction of resected DSBs and the resection lengths. However, in the absence of 53BP1, Polα activity is sustained on ssDNA yet does not substantially counter resection. In contrast, Exo1 nuclease activity is essential for hyperresection in the absence of 53BP1. Thus, 53BP1 inhibits resection mainly through end-protection rather than by promoting fill-in.
2021-09-10 | GSE181669 | GEO