RESUMO
BACKGROUND & AIMS: HBV causes hepatocellular carcinoma (HCC). While it was recently shown that the ability of HBV X protein (HBx) to impair the Smc5/6 (structural maintenance of chromosome 5/6) complex is important for viral transcription, HBx is also a potent driver of HCC. However, the mechanism by which HBx expression induces hepatocarcinogenesis is unclear. METHODS: Degradation of the Smc5/6 complex and accumulation of DNA damage were observed in both in vivo and in vitro HBV infection models. Rescue experiments were performed using nitazoxanide (NTZ), which inhibits degradation of the Smc5/6 complex by HBx. RESULTS: HBx-triggered degradation of the Smc5/6 complex causes impaired homologous recombination (HR) repair of DNA double-strand breaks (DSBs), leading to cellular transformation. We found that DNA damage accumulated in the liver tissue of HBV-infected humanized chimeric mice, HBx-transgenic mice, and human tissues. HBx suppressed the HR repair of DSBs, including that induced by the CRISPR-Cas9 system, in an Smc5/6-dependent manner, which was rescued by restoring the Smc5/6 complex. NTZ restored HR repair in, and colony formation by, HBx-expressing cells. CONCLUSIONS: Degradation of the Smc5/6 complex by HBx increases viral transcription and promotes cellular transformation by impairing HR repair of DSBs. LAY SUMMARY: The hepatitis B virus expresses a regulatory protein called HBV X protein (or HBx). This protein degrades the Smc5/6 complex in human hepatocytes, which is essential for viral replication. We found that this process also plays a key role in the accumulation of DNA damage, which contributes to HBx-mediated tumorigenesis.
Assuntos
Proteínas de Ciclo Celular/efeitos adversos , Proteínas Cromossômicas não Histona/efeitos adversos , Reparo de DNA por Recombinação/efeitos dos fármacos , Transativadores/efeitos dos fármacos , Proteínas Virais Reguladoras e Acessórias/efeitos dos fármacos , Animais , Carcinoma Hepatocelular/complicações , Carcinoma Hepatocelular/patologia , Modelos Animais de Doenças , Fígado/efeitos dos fármacos , Fígado/patologia , Neoplasias Hepáticas/complicações , Neoplasias Hepáticas/patologia , Camundongos , Reparo de DNA por Recombinação/imunologia , Estatísticas não ParamétricasRESUMO
RAD51, a multifunctional protein, plays a central role in DNA replication and homologous recombination repair, and is known to be involved in cancer development. We identified a novel role for RAD51 in innate immune response signaling. Defects in RAD51 lead to the accumulation of self-DNA in the cytoplasm, triggering a STING-mediated innate immune response after replication stress and DNA damage. In the absence of RAD51, the unprotected newly replicated genome is degraded by the exonuclease activity of MRE11, and the fragmented nascent DNA accumulates in the cytosol, initiating an innate immune response. Our data suggest that in addition to playing roles in homologous recombination-mediated DNA double-strand break repair and replication fork processing, RAD51 is also implicated in the suppression of innate immunity. Thus, our study reveals a previously uncharacterized role of RAD51 in initiating immune signaling, placing it at the hub of new interconnections between DNA replication, DNA repair, and immunity.
Assuntos
Replicação do DNA , Proteínas de Ligação a DNA/genética , DNA/genética , Proteínas de Membrana/genética , Rad51 Recombinase/genética , Reparo de DNA por Recombinação/genética , Linhagem Celular Tumoral , DNA/imunologia , Quebras de DNA de Cadeia Dupla/efeitos dos fármacos , Proteínas de Ligação a DNA/imunologia , Células Epiteliais/citologia , Células Epiteliais/efeitos dos fármacos , Células Epiteliais/imunologia , Fibroblastos/citologia , Fibroblastos/efeitos dos fármacos , Fibroblastos/imunologia , Genes Reporter , Humanos , Ácidos Hidroxâmicos/farmacologia , Imunidade Inata , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Proteína Homóloga a MRE11 , Proteínas de Membrana/imunologia , Pirimidinonas/farmacologia , Rad51 Recombinase/deficiência , Rad51 Recombinase/imunologia , Reparo de DNA por Recombinação/imunologia , Transdução de Sinais/genética , Transdução de Sinais/imunologia , Tionas/farmacologia , Vorinostat , Proteína Vermelha FluorescenteAssuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Imunoterapia/métodos , Linfócitos do Interstício Tumoral/imunologia , Neoplasias Ovarianas/tratamento farmacológico , Reparo de DNA por Recombinação/genética , Antineoplásicos Imunológicos/farmacologia , Antineoplásicos Imunológicos/uso terapêutico , Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Proteína BRCA1/genética , Proteína BRCA2/genética , Ensaios Clínicos como Assunto , Feminino , Humanos , Mutação , Neoplasias Ovarianas/genética , Neoplasias Ovarianas/imunologia , Inibidores de Poli(ADP-Ribose) Polimerases/farmacologia , Inibidores de Poli(ADP-Ribose) Polimerases/uso terapêutico , Receptor de Morte Celular Programada 1/antagonistas & inibidores , Receptor de Morte Celular Programada 1/imunologia , Reparo de DNA por Recombinação/efeitos dos fármacos , Reparo de DNA por Recombinação/imunologia , Resultado do TratamentoRESUMO
In response to a variety of cellular stresses, poly(ADP-ribose) polymerase 1 (PARP1) has vital roles in orchestrating DNA damage repair and preserving genomic integrity. Clinical activity of PARP inhibitors (PARPis) in BRCA1/2 mutant cancers validated the concept of synthetic lethality between PARP inhibition and deleterious BRCA1/2 mutations, leading to clinical approval of several PARPis. Preclinical and clinical studies aiming to broaden the therapeutic application of PARPis identified sensitivity biomarkers and rationale combination strategies that can target BRCA wild-type and homologous recombination (HR) DNA repair-proficient cancers, including central nervous system (CNS) malignancies. In this review, we summarize recent progress in PARPi therapy in brain tumors, and discuss current opportunities for, and challenges to, the use of PARPis in neuro-oncology.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Neoplasias Encefálicas/terapia , Quimiorradioterapia/métodos , Terapia Viral Oncolítica/métodos , Inibidores de Poli(ADP-Ribose) Polimerases/uso terapêutico , Animais , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Proteína BRCA1/genética , Proteína BRCA2/genética , Biomarcadores Tumorais/análise , Biomarcadores Tumorais/genética , Barreira Hematoencefálica/metabolismo , Neoplasias Encefálicas/diagnóstico , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/mortalidade , Dano ao DNA/efeitos dos fármacos , Dano ao DNA/imunologia , Dano ao DNA/efeitos da radiação , Modelos Animais de Doenças , Resistencia a Medicamentos Antineoplásicos/genética , Resistencia a Medicamentos Antineoplásicos/imunologia , Resistencia a Medicamentos Antineoplásicos/efeitos da radiação , Humanos , Camundongos , Mutação , Vírus Oncolíticos/imunologia , Permeabilidade , Poli(ADP-Ribose) Polimerase-1/metabolismo , Inibidores de Poli(ADP-Ribose) Polimerases/farmacologia , Intervalo Livre de Progressão , Reparo de DNA por Recombinação/efeitos dos fármacos , Reparo de DNA por Recombinação/imunologia , Reparo de DNA por Recombinação/efeitos da radiação , Mutações Sintéticas Letais/efeitos dos fármacos , Temozolomida/farmacologia , Temozolomida/uso terapêuticoRESUMO
Antibody class-switch DNA recombination (CSR) is initiated by AID-introduced DSBs in the switch (S) regions targeted for recombination, as effected by Ku70/Ku86-mediated NHEJ. Ku-deficient B cells, however, undergo (reduced) CSR through an alternative(A)-NHEJ pathway, which introduces microhomologies in S-S junctions. As microhomology-mediated end-joining requires annealing of single-strand DNA ends, we addressed the contribution of single-strand annealing factors HR Rad52 and translesion DNA polymerase θ to CSR. Compared with their Rad52+/+ counterparts, which display normal CSR, Rad52-/- B cells show increased CSR, fewer intra-Sµ region recombinations, no/minimal microhomologies in S-S junctions, decreased c-Myc/IgH translocations and increased Ku70/Ku86 recruitment to S-region DSB ends. Rad52 competes with Ku70/Ku86 for binding to S-region DSB ends. It also facilitates a Ku-independent DSB repair, which favours intra-S region recombination and mediates, particularly in Ku absence, inter-S-S recombination, as emphasized by the significantly greater CSR reduction in Rad52-/- versus Rad52+/+ B cells on Ku86 knockdown.