RESUMO
Transient halting of transcription activity on the damaged chromatin facilitates DNA double-strand break (DSB) repair. However, the molecular mechanisms that facilitate transcription recovery following DSB repair remain largely undefined. Notably, failure to restore gene expression in a timely manner can compromise transcriptome signatures and may impose deleterious impacts on cell identity and cell fate. Here, we report PHF8 as the major demethylase that reverses transcriptionally repressive epigenetic modification laid down by the DYRK1B-EHMT2 pathway. We found that PHF8 concentrates at laser-induced DNA damage tracks in a DYRK1B-dependent manner and promotes timely resolution of local H3K9me2 to facilitate the resumption of transcription. Moreover, PHF8 also assists in the recovery of ribosomal DNA (rDNA) transcription following the repair of nucleolar DSBs. Taken together, our findings uncover PHF8 as a key mediator that coordinates transcription activities during the recovery phase of DSB responses.
RESUMO
Pausing of RNA polymerase II (Pol II) at transcription start sites (TSSs) primes target genes for productive elongation. Coincidentally, DNA double-strand breaks (DSBs) enrich at highly transcribed and Pol II-paused genes, although their interplay remains undefined. Using androgen receptor (AR) signaling as a model, we have uncovered AR-interacting protein 4 (ARIP4) helicase as a driver of androgen-dependent transcription induction. Chromatin immunoprecipitation sequencing analysis revealed that ARIP4 preferentially co-occupies TSSs with paused Pol II. Moreover, we found that ARIP4 complexes with topoisomerase II beta and mediates transient DSB formation upon hormone stimulation. Accordingly, ARIP4 deficiency compromised release of paused Pol II and resulted in R-loop accumulation at a panel of highly transcribed AR target genes. Last, we showed that ARIP4 binds and unwinds R-loops in vitro and that its expression positively correlates with prostate cancer progression. We propose that androgen stimulation triggers ARIP4-mediated unwinding of R-loops at TSSs, enforcing Pol II pause release to effectively drive an androgen-dependent expression program.
Assuntos
Androgênios , Neoplasias da Próstata , Estruturas R-Loop , RNA Polimerase II , Receptores Androgênicos , Humanos , Androgênios/metabolismo , Receptores Androgênicos/metabolismo , Receptores Androgênicos/genética , Masculino , Neoplasias da Próstata/genética , Neoplasias da Próstata/metabolismo , Neoplasias da Próstata/patologia , RNA Polimerase II/metabolismo , RNA Polimerase II/genética , Linhagem Celular Tumoral , DNA Topoisomerases Tipo II/metabolismo , DNA Topoisomerases Tipo II/genética , Transcrição Gênica , Quebras de DNA de Cadeia Dupla , Sítio de Iniciação de Transcrição , Regulação Neoplásica da Expressão Gênica , Ligação Proteica , Ativação TranscricionalRESUMO
Acute myeloid leukemia (AML) with TP53 mutation is one of the most lethal cancers and portends an extremely poor prognosis. Based on in silico analyses of druggable genes and differential gene expression in TP53-mutated AML, we identified pololike kinase 4 (PLK4) as a novel therapeutic target and examined its expression, regulation, pathogenetic mechanisms, and therapeutic potential in TP53-mutated AML. PLK4 expression was suppressed by activated p53 signaling in TP53 wild-type AML and was increased in TP53-mutated AML cell lines and primary samples. Short-term PLK4 inhibition induced DNA damage and apoptosis in TP53 wild-type AML. Prolonged PLK4 inhibition suppressed the growth of TP53-mutated AML and was associated with DNA damage, apoptosis, senescence, polyploidy, and defective cytokinesis. A hitherto undescribed PLK4/PRMT5/EZH2/H3K27me3 axis was demonstrated in both TP53 wild-type and mutated AML, resulting in histone modification through PLK4-induced PRMT5 phosphorylation. In TP53-mutated AML, combined effects of histone modification and polyploidy activated the cGAS-STING pathway, leading to secretion of cytokines and chemokines and activation of macrophages and T cells upon coculture with AML cells. In vivo, PLK4 inhibition also induced cytokine and chemokine expression in mouse recipients, and its combination with anti-CD47 antibody, which inhibited the "don't-eat-me" signal in macrophages, synergistically reduced leukemic burden and prolonged animal survival. The study shed important light on the pathogenetic role of PLK4 and might lead to novel therapeutic strategies in TP53-mutated AML.
Assuntos
Histonas , Leucemia Mieloide Aguda , Animais , Camundongos , Histonas/metabolismo , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/metabolismo , Mutação , Metilação , Nucleotidiltransferases/metabolismo , Leucemia Mieloide Aguda/patologia , Imunidade , PoliploidiaRESUMO
Degree of genomic instability closely correlates with poor prognosis, drug resistance as well as poor survival across human cancer of different origins. This study assessed the relationship between DNA damage response (DDR) and chromosome instability in hepatocellular carcinoma (HCC). We investigated DDR signaling in HCC cells by analyzing DNA damage-dependent redistribution of major DDR proteins to damaged chromatin using immunofluorescence microscopy and Western blotting experimentations. We also performed gene conversion and metaphase analyses to address whether dysregulated DDR may bear any biological significance during hepatocarcinogenesis. Accordingly, we found that HCC cell lines suffered from elevated spontaneous DNA double-strand breaks (DSBs). In addition, analyses of HCC metaphases revealed marked aneuploidy and frequent sister chromatid exchanges when compared to immortalized hepatocytes, the latter of which were further induced following camptothecin-induced DSBs. We propose that genomic instability in HCC may be caused by erroneous DNA repair in a desperate attempt to mend DSBs for cell survival and that such preemptive measures inadvertently foster chromosome instability and thus complex genomic rearrangements.
Assuntos
Proteínas de Ligação a DNA/genética , DNA/genética , Histonas/genética , Neoplasias/genética , Proliferação de Células/genética , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas/genética , DNA/ultraestrutura , Proteínas de Ligação a DNA/ultraestrutura , Histonas/ultraestrutura , Humanos , Mutação/genética , Neoplasias/patologia , Conformação de Ácido Nucleico , Nucleossomos/genética , Oncogenes/genética , FenótipoRESUMO
PCNA is a central scaffold that coordinately assembles replication and repair machineries at DNA replication forks for faithful genome duplication. Here, we describe TRAIP (RNF206) as a novel PCNA-interacting factor that has important roles during mammalian replicative stress responses. We show that TRAIP encodes a nucleolar protein that migrates to stalled replication forks, and that this is accomplished by its targeting of PCNA via an evolutionarily conserved PIP box on its C terminus. Accordingly, inactivation of TRAIP or its interaction with the PCNA clamp compromised replication fork recovery and progression, and leads to chromosome instability. Together, our findings establish TRAIP as a component of the mammalian replicative stress response network, and implicate the TRAIP-PCNA axis in recovery of stalled replication forks.
RESUMO
UNLABELLED: Epstein-Barr virus (EBV), a type of oncogenic herpesvirus, is associated with human malignancies. Previous studies have shown that lytic reactivation of EBV in latently infected cells induces an ATM-dependent DNA damage response (DDR). The involvement of ATM activation has been implicated in inducing viral lytic gene transcription to promote lytic reactivation. Its contribution to the formation of a replication compartment during lytic reactivation of EBV remains poorly defined. In this study, the role of ATM in viral DNA replication was investigated in EBV-infected nasopharyngeal epithelial cells. We observed that induction of lytic infection of EBV triggers ATM activation and localization of DDR proteins at the viral replication compartments. Suppression of ATM activity using a small interfering RNA (siRNA) approach or a specific chemical inhibitor profoundly suppressed replication of EBV DNA and production of infectious virions in EBV-infected cells induced to undergo lytic reactivation. We further showed that phosphorylation of Sp1 at the serine-101 residue is essential in promoting the accretion of EBV replication proteins at the replication compartment, which is crucial for replication of viral DNA. Knockdown of Sp1 expression by siRNA effectively suppressed the replication of viral DNA and localization of EBV replication proteins to the replication compartments. Our study supports an important role of ATM activation in lytic reactivation of EBV in epithelial cells, and phosphorylation of Sp1 is an essential process downstream of ATM activation involved in the formation of viral replication compartments. Our study revealed an essential role of the ATM-dependent DDR pathway in lytic reactivation of EBV, suggesting a potential antiviral replication strategy using specific DDR inhibitors. IMPORTANCE: Epstein-Barr virus (EBV) is closely associated with human malignancies, including undifferentiated nasopharyngeal carcinoma (NPC), which has a high prevalence in southern China. EBV can establish either latent or lytic infection depending on the cellular context of infected host cells. Recent studies have highlighted the importance of the DNA damage response (DDR), a surveillance mechanism that evolves to maintain genome integrity, in regulating lytic EBV replication. However, the underlying molecular events are largely undefined. ATM is consistently activated in EBV-infected epithelial cells when they are induced to undergo lytic reactivation. Suppression of ATM inhibits replication of viral DNA. Furthermore, we observed that phosphorylation of Sp1 at the serine-101 residue, a downstream event of ATM activation, plays an essential role in the formation of viral replication compartments for replication of virus DNA. Our study provides new insights into the mechanism through which EBV utilizes the host cell machinery to promote replication of viral DNA upon lytic reactivation.
Assuntos
Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Células Epiteliais/virologia , Herpesvirus Humano 4/fisiologia , Interações Hospedeiro-Patógeno , Replicação Viral , Proteínas Mutadas de Ataxia Telangiectasia/antagonistas & inibidores , Proteínas Mutadas de Ataxia Telangiectasia/genética , Linhagem Celular , Enzimas Reparadoras do DNA/metabolismo , Replicação do DNA , Técnicas de Silenciamento de Genes , Humanos , Fosforilação , Processamento de Proteína Pós-Traducional , Fator de Transcrição Sp1/genética , Fator de Transcrição Sp1/metabolismoRESUMO
The Fanconi anemia (FA) pathway participates in interstrand cross-link (ICL) repair and the maintenance of genomic stability. The FA core complex consists of eight FA proteins and two Fanconi anemia-associated proteins (FAAP24 and FAAP100). The FA core complex has ubiquitin ligase activity responsible for monoubiquitination of the FANCI-FANCD2 (ID) complex, which in turn initiates a cascade of biochemical events that allow processing and removal of cross-linked DNA and thereby promotes cell survival following DNA damage. Here, we report the identification of a unique component of the FA core complex, namely, FAAP20, which contains a RAD18-like ubiquitin-binding zinc-finger domain. Our data suggest that FAAP20 promotes the functional integrity of the FA core complex via its direct interaction with the FA gene product, FANCA. Indeed, somatic knockout cells devoid of FAAP20 displayed the hallmarks of FA cells, including hypersensitivity to DNA cross-linking agents, chromosome aberrations, and reduced FANCD2 monoubiquitination. Taking these data together, our study indicates that FAAP20 is an important player involved in the FA pathway.