RESUMO
Osimertinib is a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (EGFR-TKI) approved for patients with EGFR T790M resistance mutations as first- or second-line treatment of EGFR-positive patients. Resistance to Osimertinib will inevitably develop, and the underlying mechanisms are largely unknown. In this study, we discovered that acquired resistance to Osimertinib is associated with abnormal DNA damage response (DDR) in lung adenocarcinoma cells. We discovered that the polycomb protein Lethal(3) Malignant Brain Tumor-Like Protein 1 (L3MBTL1) regulates chromatin structure, thereby contributing to DDR and Osimertinib resistance. EGFR oncogene inhibition reduced L3MBTL1 ubiquitination while stabilizing its expression in Osimertinib-resistant cells. L3MBTL1 reduction and treatment with Osimertinib significantly inhibited DDR and proliferation of Osimertinib-resistant lung cancer cells in vitro and in vivo. L3MBTL1 binds throughout the genome and plays an important role in EGFR-TKI resistance. It also competes with 53BP1 for H4K20Me2 and inhibits the development of drug resistance in Osimertinib-resistant lung cancer cells in vitro and in vivo. Our findings suggest that L3MBTL1 inhibition is a novel approach to overcoming EGFR-TKI-acquired resistance.
Assuntos
Acrilamidas , Adenocarcinoma de Pulmão , Compostos de Anilina , Dano ao DNA , Resistencia a Medicamentos Antineoplásicos , Epigênese Genética , Receptores ErbB , Neoplasias Pulmonares , Humanos , Acrilamidas/farmacologia , Resistencia a Medicamentos Antineoplásicos/genética , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Compostos de Anilina/farmacologia , Compostos de Anilina/uso terapêutico , Adenocarcinoma de Pulmão/genética , Adenocarcinoma de Pulmão/tratamento farmacológico , Adenocarcinoma de Pulmão/patologia , Adenocarcinoma de Pulmão/metabolismo , Dano ao DNA/efeitos dos fármacos , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/patologia , Neoplasias Pulmonares/metabolismo , Epigênese Genética/efeitos dos fármacos , Animais , Linhagem Celular Tumoral , Receptores ErbB/metabolismo , Receptores ErbB/genética , Camundongos , Proteínas do Grupo Polycomb/metabolismo , Proteínas do Grupo Polycomb/genética , Camundongos Nus , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Inibidores de Proteínas Quinases/farmacologia , Proliferação de Células/efeitos dos fármacos , Ubiquitinação/efeitos dos fármacos , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Indóis , PirimidinasRESUMO
Tudor Interacting Repair Regulator (TIRR) is an RNA-binding protein (RBP) that interacts directly with 53BP1, restricting its access to DNA double-strand breaks (DSBs) and its association with p53. We utilized iCLIP to identify RNAs that directly bind to TIRR within cells, identifying the long non-coding RNA NEAT1 as the primary RNA partner. The high affinity of TIRR for NEAT1 is due to prevalent G-rich motifs in the short isoform (NEAT1_1) region of NEAT1. This interaction destabilizes the TIRR/53BP1 complex, promoting 53BP1's function. NEAT1_1 is enriched during the G1 phase of the cell cycle, thereby ensuring that TIRR-dependent inhibition of 53BP1's function is cell cycle-dependent. TDP-43, an RBP that is implicated in neurodegenerative diseases, modulates the TIRR/53BP1 complex by promoting the production of the NEAT1 short isoform, NEAT1_1. Together, we infer that NEAT1_1, and factors regulating NEAT1_1, may impact 53BP1-dependent DNA repair processes, with implications for a spectrum of diseases.
Assuntos
Proteínas de Ligação a DNA , RNA Longo não Codificante , Proteínas de Ligação a RNA , Proteína 1 de Ligação à Proteína Supressora de Tumor p53 , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Humanos , Proteínas de Ligação a RNA/metabolismo , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a DNA/metabolismo , Proteínas de Ligação a DNA/genética , RNA Longo não Codificante/metabolismo , RNA Longo não Codificante/genética , Instabilidade Genômica , Quebras de DNA de Cadeia Dupla , Células HEK293 , Ligação Proteica , Reparo do DNA , Proteína Supressora de Tumor p53/metabolismo , Proteína Supressora de Tumor p53/genéticaRESUMO
DNA double strand breaks (DSBs) are critical for the efficacy of radiotherapy as they lead to cell death if not repaired. DSBs caused by ionizing radiation (IR) initiate histone modifications and accumulate DNA repair proteins, including 53BP1, which forms distinct foci at damage sites and serves as a marker for DSBs. DSB repair primarily occurs through Non-Homologous End Joining (NHEJ) and Homologous Recombination (HR). NHEJ directly ligates DNA ends, employing proteins such as DNA-PKcs, while HR, involving proteins such as Rad54, uses a sister chromatid template for accurate repair and functions in the S and G2 phases of the cell cycle. Both pathways are crucial, as illustrated by the IR sensitivity in cells lacking DNA-PKcs or Rad54. We generated mouse embryonic stem (mES) cells which are knockout (KO) for DNA-PKcs and Rad54 to explore the combined role of HR and NHEJ in DSB repair. We found that cells lacking both DNA-PKcs and Rad54 are hypersensitive to X-ray radiation, coinciding with impaired 53BP1 focus resolution and a more persistent G2 phase cell cycle block. Additionally, mES cells deficient in DNA-PKcs or both DNA-PKcs and Rad54 exhibit an increased nuclear size approximately 18-24 h post-irradiation. To further explore the role of Rad54 in the absence of DNA-PKcs, we generated DNA-PKcs KO mES cells expressing GFP-tagged wild-type (WT) or ATPase-defective Rad54 to track the Rad54 foci over time post-irradiation. Cells lacking DNA-PKcs and expressing ATPase-defective Rad54 exhibited a similar phenotypic response to IR as those lacking both DNA-PKcs and Rad54. Despite a strong G2 phase arrest, live-cell imaging showed these cells eventually progress through mitosis, forming micronuclei. Additionally, mES cells lacking DNA-PKcs showed increased Rad54 foci over time post-irradiation, indicating an enhanced reliance on HR for DSB repair without DNA-PKcs. Our findings underscore the essential roles of HR and NHEJ in maintaining genomic stability post-IR in mES cells. The interplay between these pathways is crucial for effective DSB repair and cell cycle progression, highlighting potential targets for enhancing radiotherapy outcomes.
Assuntos
Quebras de DNA de Cadeia Dupla , Reparo do DNA por Junção de Extremidades , Recombinação Homóloga , Células-Tronco Embrionárias Murinas , Radiação Ionizante , Animais , Camundongos , Reparo do DNA por Junção de Extremidades/efeitos da radiação , Quebras de DNA de Cadeia Dupla/efeitos da radiação , Células-Tronco Embrionárias Murinas/metabolismo , Células-Tronco Embrionárias Murinas/efeitos da radiação , Células-Tronco Embrionárias Murinas/citologia , Recombinação Homóloga/efeitos da radiação , Proteína Quinase Ativada por DNA/metabolismo , Proteína Quinase Ativada por DNA/genética , DNA Helicases/metabolismo , DNA Helicases/genética , Proteínas de Ligação a DNA/metabolismo , Proteínas de Ligação a DNA/genética , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Proteínas NuclearesRESUMO
53BP1 is a well-established DNA damage repair factor that has recently emerged to critically regulate gene expression for tumor suppression and neural development. However, its precise function and regulatory mechanisms remain unclear. Here, we showed that phosphorylation of 53BP1 at serine 25 by ATM is required for neural progenitor cell proliferation and neuronal differentiation in cortical brain organoids. Dynamic phosphorylation of 53BP1-serine 25 controls 53BP1 target genes governing neuronal differentiation and function, cellular response to stress, and apoptosis. Mechanistically, ATM and RNF168 govern 53BP1's binding to gene loci to directly affect gene regulation, especially at genes for neuronal differentiation and maturation. 53BP1 serine 25 phosphorylation effectively impedes its binding to bivalent or H3K27me3-occupied promoters, especially at genes regulating H3K4 methylation, neuronal functions, and cell proliferation. Beyond 53BP1, ATM-dependent phosphorylation displays wide-ranging effects, regulating factors in neuronal differentiation, cytoskeleton, p53 regulation, as well as key signaling pathways such as ATM, BDNF, and WNT during cortical organoid differentiation. Together, our data suggest that the interplay between 53BP1 and ATM orchestrates essential genetic programs for cell morphogenesis, tissue organization, and developmental pathways crucial for human cortical development.
Assuntos
Proteínas Mutadas de Ataxia Telangiectasia , Organoides , Proteína 1 de Ligação à Proteína Supressora de Tumor p53 , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Organoides/metabolismo , Humanos , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Proteínas Mutadas de Ataxia Telangiectasia/genética , Fosforilação , Dano ao DNA , Córtex Cerebral/metabolismo , Córtex Cerebral/citologia , Células-Tronco Neurais/metabolismo , Diferenciação Celular/genética , Proliferação de Células , Reparo do DNA , Neurogênese/genética , Neurônios/metabolismo , Transdução de SinaisRESUMO
Although previous studies have reported that pre-mRNA splicing factors (SFs) are involved in the repair of DNA double-strand breaks (DSBs) via homologous recombination (HR), their exact role in promoting HR remains poorly understood. Here, we showed that SART1, an SF upregulated in several types of cancer, promotes DSB end resection, an essential first step of HR. The resection-promoting function of SART1 requires phosphorylation at threonine 430 and 695 by ATM/ATR. SART1 is recruited to DSB sites in a manner dependent on transcription and its RS domain. SART1 is epistatic with BRCA1, a major HR factor, in the promotion of resection, especially transcription-associated resection in the G2 phase. SART1 and BRCA1 accumulate at DSB sites in an interdependent manner, and epistatically counteract the resection blockade posed by 53BP1 and RIF1. Furthermore, chromosome analysis demonstrated that SART1 and BRCA1 epistatically suppressed genomic alterations caused by DSB misrepair in the G2 phase. Collectively, these results indicate that SART1 and BRCA1 cooperatively facilitate resection of DSBs arising in transcriptionally active genomic regions in the G2 phase, thereby promoting faithful repair by HR, and suppressing genome instability.
Assuntos
Proteína BRCA1 , Quebras de DNA de Cadeia Dupla , Reparo de DNA por Recombinação , Proteína BRCA1/metabolismo , Proteína BRCA1/genética , Humanos , Fatores de Processamento de Serina-Arginina/metabolismo , Fatores de Processamento de Serina-Arginina/genética , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Proteínas Mutadas de Ataxia Telangiectasia/genética , Fosforilação , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Linhagem Celular Tumoral , Proteínas de Ligação a Telômeros/metabolismo , Proteínas de Ligação a Telômeros/genética , Epistasia Genética , Fase G2/genéticaRESUMO
53BP1 nucleates the anti-end resection machinery at DNA double-strand breaks, thereby countering BRCA1 activity. Loss of 53BP1 leads to DNA end processing and homologous recombination in BRCA1-deficient cells. Consequently, BRCA1-mutant tumors, typically sensitive to PARP inhibitors (PARPi), become resistant in the absence of 53BP1. Here, we demonstrate that the 'leaky' DNA end resection in the absence of 53BP1 results in increased micronuclei and cytoplasmic double-stranded DNA, leading to activation of the cGAS-STING pathway and pro-inflammatory signaling. This enhances CD8+ T cell infiltration, activates macrophages and natural killer cells, and impedes tumor growth. Loss of 53BP1 correlates with a response to immune checkpoint blockade (ICB) and improved overall survival. Immunohistochemical assessment of 53BP1 in two malignancies, high grade serous ovarian cancer and pancreatic ductal adenocarcinoma, which are refractory to ICBs, reveals that lower 53BP1 levels correlate with an increased adaptive and innate immune response. Finally, BRCA1-deficient tumors that develop resistance to PARPi due to the loss of 53BP1 are susceptible to ICB. Therefore, we conclude that 53BP1 is critical for tumor immunogenicity and underpins the response to ICB. Our results support including 53BP1 expression as an exploratory biomarker in ICB trials for malignancies typically refractory to immunotherapy.
Assuntos
Proteínas de Membrana , Nucleotidiltransferases , Neoplasias Ovarianas , Neoplasias Pancreáticas , Proteína 1 de Ligação à Proteína Supressora de Tumor p53 , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Feminino , Nucleotidiltransferases/metabolismo , Nucleotidiltransferases/genética , Proteínas de Membrana/metabolismo , Proteínas de Membrana/genética , Humanos , Animais , Neoplasias Ovarianas/imunologia , Neoplasias Ovarianas/genética , Neoplasias Ovarianas/patologia , Neoplasias Ovarianas/metabolismo , Neoplasias Pancreáticas/imunologia , Neoplasias Pancreáticas/genética , Neoplasias Pancreáticas/patologia , Neoplasias Pancreáticas/metabolismo , Camundongos , Linhagem Celular Tumoral , Quebras de DNA de Cadeia Dupla , Proteína BRCA1/metabolismo , Proteína BRCA1/genética , Transdução de Sinais , Linfócitos T CD8-Positivos/imunologia , Inibidores de Checkpoint Imunológico/uso terapêutico , Inibidores de Checkpoint Imunológico/farmacologia , Inibidores de Poli(ADP-Ribose) Polimerases/farmacologia , Inibidores de Poli(ADP-Ribose) Polimerases/uso terapêutico , Camundongos Endogâmicos C57BL , Células Matadoras Naturais/imunologia , Células Matadoras Naturais/metabolismo , Camundongos Knockout , Carcinoma Ductal Pancreático/imunologia , Carcinoma Ductal Pancreático/genética , Carcinoma Ductal Pancreático/patologia , Imunidade InataRESUMO
DNA double-strand breaks (DSBs) elicit an elaborate response to signal damage and trigger repair via two major pathways: nonhomologous end-joining (NHEJ), which functions throughout the interphase, and homologous recombination (HR), restricted to S/G2 phases. The DNA damage response relies, on post-translational modifications of nuclear factors to coordinate the mending of breaks. Ubiquitylation of histones and chromatin-associated factors regulates DSB repair and numerous E3 ubiquitin ligases are involved in this process. Despite significant progress, our understanding of ubiquitin-mediated DNA damage response regulation remains incomplete. Here, we have performed a localization screen to identify RING/U-box E3 ligases involved in genome maintenance. Our approach uncovered 7 novel E3 ligases that are recruited to microirradiation stripes, suggesting potential roles in DNA damage signaling and repair. Among these factors, the DELTEX family E3 ligase DTX2 is rapidly mobilized to lesions in a poly ADP-ribosylation-dependent manner. DTX2 is recruited and retained at DSBs via its WWE and DELTEX conserved C-terminal domains. In cells, both domains are required for optimal binding to mono and poly ADP-ribosylated proteins with WWEs playing a prominent role in this process. Supporting its involvement in DSB repair, DTX2 depletion decreases HR efficiency and moderately enhances NHEJ. Furthermore, DTX2 depletion impeded BRCA1 foci formation and increased 53BP1 accumulation at DSBs, suggesting a fine-tuning role for this E3 ligase in repair pathway choice. Finally, DTX2 depletion sensitized cancer cells to X-rays and PARP inhibition and these susceptibilities could be rescued by DTX2 reexpression. Altogether, our work identifies DTX2 as a novel ADP-ribosylation-dependent regulator of HR-mediated DSB repair.
Assuntos
Quebras de DNA de Cadeia Dupla , Ubiquitina-Proteína Ligases , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitina-Proteína Ligases/genética , Humanos , ADP-Ribosilação , Reparo do DNA , Reparo do DNA por Junção de Extremidades , Proteína BRCA1/metabolismo , Proteína BRCA1/genética , Ubiquitinação , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genéticaRESUMO
Mitotic errors generate micronuclei entrapping mis-segregated chromosomes, which are susceptible to catastrophic fragmentation through chromothripsis. The reassembly of fragmented chromosomes by error-prone DNA double-strand break (DSB) repair generates diverse genomic rearrangements associated with human diseases. How specific repair pathways recognize and process these lesions remains poorly understood. Here we use CRISPR/Cas9 to systematically inactivate distinct DSB repair pathways and interrogate the rearrangement landscape of fragmented chromosomes. Deletion of canonical non-homologous end joining (NHEJ) components substantially reduces complex rearrangements and shifts the rearrangement landscape toward simple alterations without the characteristic patterns of chromothripsis. Following reincorporation into the nucleus, fragmented chromosomes localize within sub-nuclear micronuclei bodies (MN bodies) and undergo ligation by NHEJ within a single cell cycle. In the absence of NHEJ, chromosome fragments are rarely engaged by alternative end-joining or recombination-based mechanisms, resulting in delayed repair kinetics, persistent 53BP1-labeled MN bodies, and cell cycle arrest. Thus, we provide evidence supporting NHEJ as the exclusive DSB repair pathway generating complex rearrangements from mitotic errors.
Assuntos
Sistemas CRISPR-Cas , Cromotripsia , Quebras de DNA de Cadeia Dupla , Reparo do DNA por Junção de Extremidades , Mitose , Mitose/genética , Humanos , Rearranjo Gênico , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Micronúcleos com Defeito CromossômicoRESUMO
Poly(ADP-ribose) polymerase inhibitors (PARPis) exhibit remarkable anticancer activity in tumors with homologous recombination (HR) gene mutations. However, the role of other DNA repair proteins in PARPi-induced lethality remains elusive. Here, we reveal that FANCM promotes PARPi resistance independent of the core Fanconi anemia (FA) complex. FANCM-depleted cells retain HR proficiency, acting independently of BRCA1 in response to PARPis. FANCM depletion leads to increased DNA damage in the second S phase after PARPi exposure, driven by elevated single-strand DNA (ssDNA) gap formation behind replication forks in the first S phase. These gaps arise from both 53BP1- and primase and DNA directed polymerase (PRIMPOL)-dependent mechanisms. Notably, FANCM-depleted cells also exhibit reduced resection of collapsed forks, while 53BP1 deletion restores resection and mitigates PARPi sensitivity. Our results suggest that FANCM counteracts 53BP1 to repair PARPi-induced DNA damage. Furthermore, FANCM depletion leads to increased chromatin bridges and micronuclei formation after PARPi treatment, elucidating the mechanism underlying extensive cell death in FANCM-depleted cells.
Assuntos
DNA de Cadeia Simples , Inibidores de Poli(ADP-Ribose) Polimerases , Proteína 1 de Ligação à Proteína Supressora de Tumor p53 , Inibidores de Poli(ADP-Ribose) Polimerases/farmacologia , Humanos , DNA de Cadeia Simples/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , DNA Helicases/metabolismo , DNA Helicases/genética , Dano ao DNA , Reparo do DNA/efeitos dos fármacos , Recombinação Homóloga/efeitos dos fármacos , Proteína BRCA1/metabolismo , Proteína BRCA1/genética , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos/genética , Linhagem Celular TumoralRESUMO
Rapid accumulation of repair factors at DNA double-strand breaks (DSBs) is essential for DSB repair. Several factors involved in DSB repair have been found undergoing liquid-liquid phase separation (LLPS) at DSB sites to facilitate DNA repair. RNF168, a RING-type E3 ubiquitin ligase, catalyzes H2A.X ubiquitination for recruiting DNA repair factors. Yet, whether RNF168 undergoes LLPS at DSB sites remains unclear. Here, we identified K63-linked polyubiquitin-triggered RNF168 condensation which further promoted RNF168-mediated DSB repair. RNF168 formed liquid-like condensates upon irradiation in the nucleus while purified RNF168 protein also condensed in vitro. An intrinsically disordered region containing amino acids 460-550 was identified as the essential domain for RNF168 condensation. Interestingly, LLPS of RNF168 was significantly enhanced by K63-linked polyubiquitin chains, and LLPS largely enhanced the RNF168-mediated H2A.X ubiquitination, suggesting a positive feedback loop to facilitate RNF168 rapid accumulation and its catalytic activity. Functionally, LLPS deficiency of RNF168 resulted in delayed recruitment of 53BP1 and BRCA1 and subsequent impairment in DSB repair. Taken together, our finding demonstrates the pivotal effect of LLPS in RNF168-mediated DSB repair.
Assuntos
Reparo do DNA , Ubiquitina-Proteína Ligases , Humanos , Quebras de DNA de Cadeia Dupla , Histonas/metabolismo , Histonas/genética , Poliubiquitina/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Ubiquitina/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitina-Proteína Ligases/genética , UbiquitinaçãoRESUMO
G0-G1 phase alternative end joining (A-EJ) is a recently defined mutagenic pathway characterized by resected deletion and translocation joints that are predominantly direct and are distinguished from A-EJ in cycling cells that rely much more on microhomology-mediated end joining (MMEJ). Using chemical and genetic approaches, we systematically evaluate potential A-EJ factors and DNA damage response (DDR) genes to support this mechanism by mapping the repair fates of RAG1/2-initiated double-strand breaks in the context of Igκ locus V-J recombination and chromosome translocation. Our findings highlight a polymerase theta-independent Parp1-XRCC1/LigIII axis as central A-EJ components, supported by 53BP1 in the context of an Ataxia-telangiectasia mutated (ATM)-activated DDR. Mechanistically, we demonstrate varied changes in short-range resection, MMEJ, and translocation, imposed by compromising specific DDR activities, which include polymerase alpha, Ataxia-telangiectasia and Rad3-related (ATR), DNA2, and Mre11. This study advances our understanding of DNA damage repair within the 53BP1 regulatory domain and the RAG1/2 postcleavage complex.
Assuntos
Proteínas Mutadas de Ataxia Telangiectasia , Reparo do DNA por Junção de Extremidades , Proteína 1 de Ligação à Proteína Supressora de Tumor p53 , Recombinação V(D)J , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Proteínas Mutadas de Ataxia Telangiectasia/genética , Animais , Humanos , Quebras de DNA de Cadeia Dupla , Camundongos , Dano ao DNA , Translocação GenéticaRESUMO
RAD18 is an E3 ubiquitin ligase that prevents replication fork collapse by promoting DNA translesion synthesis and template switching. Besides this classical role, RAD18 has been implicated in homologous recombination; however, this function is incompletely understood. Here, we show that RAD18 is recruited to DNA lesions by monoubiquitination of histone H2A at K15 and counteracts accumulation of 53BP1. Super-resolution microscopy revealed that RAD18 localizes to the proximity of DNA double strand breaks and limits the distribution of 53BP1 to the peripheral chromatin nanodomains. Whereas auto-ubiquitination of RAD18 mediated by RAD6 inhibits its recruitment to DNA breaks, interaction with SLF1 promotes RAD18 accumulation at DNA breaks in the post-replicative chromatin by recognition of histone H4K20me0. Surprisingly, suppression of 53BP1 function by RAD18 is not involved in homologous recombination and rather leads to reduction of non-homologous end joining. Instead, we provide evidence that RAD18 promotes HR repair by recruiting the SMC5/6 complex to DNA breaks. Finally, we identified several new loss-of-function mutations in RAD18 in cancer patients suggesting that RAD18 could be involved in cancer development.
Assuntos
Cromatina , Quebras de DNA de Cadeia Dupla , Proteínas de Ligação a DNA , Histonas , Proteína 1 de Ligação à Proteína Supressora de Tumor p53 , Ubiquitina-Proteína Ligases , Ubiquitinação , Humanos , Cromatina/metabolismo , Cromatina/genética , Proteínas de Ligação a DNA/metabolismo , Proteínas de Ligação a DNA/genética , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitina-Proteína Ligases/genética , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Histonas/metabolismo , Recombinação Homóloga/genética , Reparo de DNA por Recombinação , Replicação do DNA , Reparo do DNA , Proteínas de Ciclo Celular/metabolismo , Proteínas de Ciclo Celular/genética , Reparo do DNA por Junção de ExtremidadesRESUMO
Maintenance of genome integrity requires tight control of DNA damage response (DDR) signalling and repair, with phosphorylation and ubiquitination representing key elements. How these events are coordinated to achieve productive DNA repair remains elusive. Here we identify the ubiquitin-conjugating enzyme UBE2D3 as a regulator of ATM kinase-induced DDR that promotes non-homologous end-joining (NHEJ) at telomeres. UBE2D3 contributes to DDR-induced chromatin ubiquitination and recruitment of the NHEJ-promoting factor 53BP1, both mediated by RNF168 upon ATM activation. Additionally, UBE2D3 promotes NHEJ by limiting RNF168 accumulation and facilitating ATM-mediated phosphorylation of KAP1-S824. Mechanistically, defective KAP1-S824 phosphorylation and telomeric NHEJ upon UBE2D3-deficiency are linked to RNF168 hyperaccumulation and aberrant PP2A phosphatase activity. Together, our results identify UBE2D3 as a multi-level regulator of NHEJ that orchestrates ATM and RNF168 activities. Moreover, they reveal a negative regulatory circuit in the DDR that is constrained by UBE2D3 and consists of RNF168- and phosphatase-mediated restriction of KAP1 phosphorylation.
Assuntos
Proteínas Mutadas de Ataxia Telangiectasia , Reparo do DNA por Junção de Extremidades , Transdução de Sinais , Proteína 28 com Motivo Tripartido , Proteína 1 de Ligação à Proteína Supressora de Tumor p53 , Enzimas de Conjugação de Ubiquitina , Ubiquitina-Proteína Ligases , Ubiquitinação , Enzimas de Conjugação de Ubiquitina/metabolismo , Enzimas de Conjugação de Ubiquitina/genética , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Proteínas Mutadas de Ataxia Telangiectasia/genética , Humanos , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitina-Proteína Ligases/genética , Fosforilação , Proteína 28 com Motivo Tripartido/metabolismo , Proteína 28 com Motivo Tripartido/genética , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Células HEK293 , Telômero/metabolismo , Dano ao DNA , Cromatina/metabolismo , AnimaisRESUMO
Histone H2AX plays a key role in DNA damage signalling in the surrounding regions of DNA double-strand breaks (DSBs). In response to DNA damage, H2AX becomes phosphorylated on serine residue 139 (known as γH2AX), resulting in the recruitment of the DNA repair effectors 53BP1 and BRCA1. Here, by studying resistance to poly(ADP-ribose) polymerase (PARP) inhibitors in BRCA1/2-deficient mammary tumours, we identify a function for γH2AX in orchestrating drug-induced replication fork degradation. Mechanistically, γH2AX-driven replication fork degradation is elicited by suppressing CtIP-mediated fork protection. As a result, H2AX loss restores replication fork stability and increases chemoresistance in BRCA1/2-deficient tumour cells without restoring homology-directed DNA repair, as highlighted by the lack of DNA damage-induced RAD51 foci. Furthermore, in the attempt to discover acquired genetic vulnerabilities, we find that ATM but not ATR inhibition overcomes PARP inhibitor (PARPi) resistance in H2AX-deficient tumours by interfering with CtIP-mediated fork protection. In summary, our results demonstrate a role for H2AX in replication fork biology in BRCA-deficient tumours and establish a function of H2AX separable from its classical role in DNA damage signalling and DSB repair.
Assuntos
Proteína BRCA1 , Proteína BRCA2 , Replicação do DNA , Resistencia a Medicamentos Antineoplásicos , Histonas , Inibidores de Poli(ADP-Ribose) Polimerases , Animais , Feminino , Humanos , Camundongos , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Proteínas Mutadas de Ataxia Telangiectasia/genética , Proteína BRCA1/metabolismo , Proteína BRCA1/deficiência , Proteína BRCA1/genética , Proteína BRCA2/metabolismo , Proteína BRCA2/genética , Proteína BRCA2/deficiência , Neoplasias da Mama/genética , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Neoplasias da Mama/tratamento farmacológico , Proteínas de Transporte/metabolismo , Proteínas de Transporte/genética , Linhagem Celular Tumoral , Quebras de DNA de Cadeia Dupla , Dano ao DNA , Reparo do DNA , Replicação do DNA/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos/genética , Histonas/metabolismo , Inibidores de Poli(ADP-Ribose) Polimerases/farmacologia , Rad51 Recombinase/metabolismo , Rad51 Recombinase/genética , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Camundongos NusRESUMO
The master DNA damage repair histone protein, H2AX, is essential for orchestrating the recruitment of downstream mediator and effector proteins at damaged chromatin. The phosphorylation of H2AX at S139, γH2AX, is well-studied for its DNA repair function. However, the extended C-terminal tail is not characterized. Here, we define the minimal motif on H2AX for the canonical function in activating the MDC1-RNF8-RNF168 phosphorylation-ubiquitination pathway that is important for recruiting repair proteins, such as 53BP1 and BRCA1. Interestingly, H2AX recruits 53BP1 independently from the MDC1-RNF8-RNF168 pathway through its evolved C-terminal linker region with S139 phosphorylation. Mechanistically, 53BP1 recruitment to damaged chromatin is mediated by the interaction between the H2AX C-terminal tail and the 53BP1 Oligomerization-Tudor domains. Moreover, γH2AX-linker mediated 53BP1 recruitment leads to camptothecin resistance in H2AX knockout cells. Overall, our study uncovers an evolved mechanism within the H2AX C-terminal tail for regulating DNA repair proteins at damaged chromatin.
Assuntos
Cromatina , Dano ao DNA , Histonas , Proteína 1 de Ligação à Proteína Supressora de Tumor p53 , Ubiquitinação , Humanos , Proteínas Adaptadoras de Transdução de Sinal , Proteína BRCA1/metabolismo , Proteína BRCA1/genética , Camptotecina/farmacologia , Proteínas de Ciclo Celular , Cromatina/metabolismo , Reparo do DNA , Células HEK293 , Histonas/metabolismo , Histonas/genética , Fosforilação , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitina-Proteína Ligases/genéticaRESUMO
Mitotic duration is tightly constrained, and extended mitosis is characteristic of problematic cells prone to chromosome missegregation and genomic instability. We show here that mitotic extension leads to the formation of p53-binding protein 1 (53BP1)-ubiquitin-specific protease 28 (USP28)-p53 protein complexes that are transmitted to, and stably retained by, daughter cells. Complexes assembled through a Polo-like kinase 1-dependent mechanism during extended mitosis and elicited a p53 response in G1 that prevented the proliferation of the progeny of cells that experienced an approximately threefold extended mitosis or successive less extended mitoses. The ability to monitor mitotic extension was lost in p53-mutant cancers and some p53-wild-type (p53-WT) cancers, consistent with classification of TP53BP1 and USP28 as tumor suppressors. Cancers retaining the ability to monitor mitotic extension exhibited sensitivity to antimitotic agents.
Assuntos
Proliferação de Células , Mitose , Neoplasias , Proteína 1 de Ligação à Proteína Supressora de Tumor p53 , Ubiquitina Tiolesterase , Humanos , Proliferação de Células/genética , Instabilidade Genômica , Mitose/efeitos dos fármacos , Mitose/genética , Neoplasias/genética , Neoplasias/patologia , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/metabolismo , Ubiquitina Tiolesterase/genética , Ubiquitina Tiolesterase/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Linhagem Celular Tumoral , Quinase 1 Polo-Like/metabolismo , Antimitóticos/farmacologia , Resistencia a Medicamentos AntineoplásicosRESUMO
Reprogramming to pluripotency is associated with DNA damage and requires the functions of the BRCA1 tumor suppressor. Here, we leverage separation-of-function mutations in BRCA1/2 as well as the physical and/or genetic interactions between BRCA1 and its associated repair proteins to ascertain the relevance of homology-directed repair (HDR), stalled fork protection (SFP), and replication gap suppression (RGS) in somatic cell reprogramming. Surprisingly, loss of SFP and RGS is inconsequential for the transition to pluripotency. In contrast, cells deficient in HDR, but proficient in SFP and RGS, reprogram with reduced efficiency. Conversely, the restoration of HDR function through inactivation of 53bp1 rescues reprogramming in Brca1-deficient cells, and 53bp1 loss leads to elevated HDR and enhanced reprogramming in mouse and human cells. These results demonstrate that somatic cell reprogramming is especially dependent on repair of replication-associated double-strand breaks (DSBs) by the HDR activity of BRCA1 and BRCA2 and can be improved in the absence of 53BP1.
Assuntos
Proteína BRCA1 , Reprogramação Celular , Quebras de DNA de Cadeia Dupla , Reparo do DNA , Proteína 1 de Ligação à Proteína Supressora de Tumor p53 , Animais , Humanos , Camundongos , Proteína BRCA1/metabolismo , Proteína BRCA1/genética , Replicação do DNA , Reparo de DNA por Recombinação , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genéticaRESUMO
RNF168 plays a central role in the DNA damage response (DDR) by ubiquitylating histone H2A at K13 and K15. These modifications direct BRCA1-BARD1 and 53BP1 foci formation in chromatin, essential for cell-cycle-dependent DNA double-strand break (DSB) repair pathway selection. The mechanism by which RNF168 catalyzes the targeted accumulation of H2A ubiquitin conjugates to form repair foci around DSBs remains unclear. Here, using cryoelectron microscopy (cryo-EM), nuclear magnetic resonance (NMR) spectroscopy, and functional assays, we provide a molecular description of the reaction cycle and dynamics of RNF168 as it modifies the nucleosome and recognizes its ubiquitylation products. We demonstrate an interaction of a canonical ubiquitin-binding domain within full-length RNF168, which not only engages ubiquitin but also the nucleosome surface, clarifying how such site-specific ubiquitin recognition propels a signal amplification loop. Beyond offering mechanistic insights into a key DDR protein, our study aids in understanding site specificity in both generating and interpreting chromatin ubiquitylation.
Assuntos
Nucleossomos , Ubiquitina-Proteína Ligases , Nucleossomos/genética , Microscopia Crioeletrônica , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitinação , Histonas/metabolismo , Cromatina/genética , Reparo do DNA , Ubiquitina/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Dano ao DNARESUMO
Methyl-lysine reader p53 binding protein 1 (53BP1) is a central mediator of DNA break repair and is associated with various human diseases, including cancer. Thus, high-quality 53BP1 chemical probes can aid in further understanding the role of 53BP1 in genome repair pathways. Herein, we utilized focused DNA-encoded library screening to identify the novel hit compound UNC8531, which binds the 53BP1 tandem Tudor domain (TTD) with an IC50 of 0.47 ± 0.09 µM in a TR-FRET assay and Kd values of 0.85 ± 0.17 and 0.79 ± 0.52 µM in ITC and SPR, respectively. UNC8531 was cocrystallized with the 53BP1 TTD to guide further optimization efforts, leading to UNC9512. NanoBRET and 53BP1-dependent foci formation experiments confirmed cellular target engagement. These results show that UNC9512 is a best-in-class small molecule 53BP1 antagonist that can aid further studies investigating the role of 53BP1 in DNA repair, gene editing, and oncogenesis.
Assuntos
Reparo do DNA , Peptídeos e Proteínas de Sinalização Intracelular , Humanos , DNA , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/química , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Domínio TudorRESUMO
Repair of DSB induced by IR is primarily carried out by Non-Homologous End Joining (NHEJ), a pathway in which 53BP1 plays a key role. We have discovered that the EMT-inducing transcriptional repressor ZEB1 (i) interacts with 53BP1 and that this interaction occurs rapidly and is significantly amplified following exposure of cells to IR; (ii) is required for the localization of 53BP1 to a subset of double-stranded breaks, and for physiological DSB repair; (iii) co-localizes with 53BP1 at IR-induced foci (IRIF); (iv) promotes NHEJ and inhibits Homologous Recombination (HR); (v) depletion increases resection at DSBs and (vi) confers PARP inhibitor (PARPi) sensitivity on BRCA1-deficient cells. Lastly, ZEB1's effects on repair pathway choice, resection, and PARPi sensitivity all rely on its homeodomain. In contrast to the well-characterized therapeutic resistance of high ZEB1-expressing cancer cells, the novel ZEB1-53BP1-shieldin resection axis described here exposes a therapeutic vulnerability: ZEB1 levels in BRCA1-deficient tumors may serve as a predictive biomarker of response to PARPis.