RESUMEN
Transcription-blocking DNA lesions are specifically targeted by transcription-coupled nucleotide excision repair (TC-NER), which removes a broad spectrum of DNA lesions to preserve transcriptional output and thereby cellular homeostasis to counteract aging. TC-NER is initiated by the stalling of RNA polymerase II at DNA lesions, which triggers the assembly of the TC-NER-specific proteins CSA, CSB and UVSSA. CSA, a WD40-repeat containing protein, is the substrate receptor subunit of a cullin-RING ubiquitin ligase complex composed of DDB1, CUL4A/B and RBX1 (CRL4CSA). Although ubiquitination of several TC-NER proteins by CRL4CSA has been reported, it is still unknown how this complex is regulated. To unravel the dynamic molecular interactions and the regulation of this complex, we apply a single-step protein-complex isolation coupled to mass spectrometry analysis and identified DDA1 as a CSA interacting protein. Cryo-EM analysis shows that DDA1 is an integral component of the CRL4CSA complex. Functional analysis reveals that DDA1 coordinates ubiquitination dynamics during TC-NER and is required for efficient turnover and progression of this process.
Asunto(s)
Reparación del ADN , Proteínas de Unión al ADN , Transcripción Genética , Ubiquitinación , Humanos , Proteínas de Unión al ADN/metabolismo , Proteínas de Unión al ADN/genética , Proteínas Cullin/metabolismo , Proteínas Cullin/genética , Enzimas Reparadoras del ADN/metabolismo , Enzimas Reparadoras del ADN/genética , Microscopía por Crioelectrón , Células HEK293 , Ubiquitina-Proteína Ligasas/metabolismo , Ubiquitina-Proteína Ligasas/genética , Proteínas de Unión a Poli-ADP-Ribosa/metabolismo , Proteínas de Unión a Poli-ADP-Ribosa/genética , Daño del ADN , ARN Polimerasa II/metabolismo , Unión Proteica , Reparación por Escisión , Proteínas Portadoras , ADN Helicasas , Factores de Transcripción , Receptores de Interleucina-17RESUMEN
Phototoxicity and skin cancer are severe adverse effects of the anti-fungal drug Voriconazole (VOR). These adverse effects resemble those seen in xeroderma pigmentosum (XP), caused by defective DNA nucleotide excision repair (NER), and we show that VOR decreases NER capacity. We show that VOR treatment does not perturb the expression of NER, or other DNA damage-related genes, but that VOR localizes to heterochromatin, in complexes containing histone acetyltransferase GCN5. Impairment of GCN5 binding to histone H3 reduced acetylation of H3, restricting damage-dependent chromatin unfolding, thereby reducing NER initiation. Restoration of H3 histone acetylation using histone deacetylase inhibitors (HDACi), rescued VOR-induced NER repression, thus offering a preventive therapeutic option. These findings underline the importance of DNA damage-dependent chromatin remodeling as an important prerequisite of functional DNA repair.
RESUMEN
Congenital nucleotide excision repair (NER) deficiency gives rise to several cancer-prone and/or progeroid disorders. It is not understood how defects in the same DNA repair pathway cause different disease features and severity. Here, we show that the absence of functional ERCC1-XPF or XPG endonucleases leads to stable and prolonged binding of the transcription/DNA repair factor TFIIH to DNA damage, which correlates with disease severity and induces senescence features in human cells. In vivo, in C. elegans, this prolonged TFIIH binding to non-excised DNA damage causes developmental arrest and neuronal dysfunction, in a manner dependent on transcription-coupled NER. NER factors XPA and TTDA both promote stable TFIIH DNA binding and their depletion therefore suppresses these severe phenotypical consequences. These results identify stalled NER intermediates as pathogenic to cell functionality and organismal development, which can in part explain why mutations in XPF or XPG cause different disease features than mutations in XPA or TTDA.
Asunto(s)
Caenorhabditis elegans , Daño del ADN , Reparación del ADN , Proteínas de Unión al ADN , Endonucleasas , Factor de Transcripción TFIIH , Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/genética , Humanos , Animales , Factor de Transcripción TFIIH/metabolismo , Factor de Transcripción TFIIH/genética , Proteínas de Unión al ADN/metabolismo , Proteínas de Unión al ADN/genética , Endonucleasas/metabolismo , Endonucleasas/genética , Proteínas de Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteína de la Xerodermia Pigmentosa del Grupo A/metabolismo , Proteína de la Xerodermia Pigmentosa del Grupo A/genética , Unión Proteica , Factores de Transcripción/metabolismo , Factores de Transcripción/genética , Mutación , Proteínas Nucleares/metabolismo , Proteínas Nucleares/genéticaRESUMEN
DNA-protein crosslinks (DPCs) arise from enzymatic intermediates, metabolism or chemicals like chemotherapeutics. DPCs are highly cytotoxic as they impede DNA-based processes such as replication, which is counteracted through proteolysis-mediated DPC removal by spartan (SPRTN) or the proteasome. However, whether DPCs affect transcription and how transcription-blocking DPCs are repaired remains largely unknown. Here we show that DPCs severely impede RNA polymerase II-mediated transcription and are preferentially repaired in active genes by transcription-coupled DPC (TC-DPC) repair. TC-DPC repair is initiated by recruiting the transcription-coupled nucleotide excision repair (TC-NER) factors CSB and CSA to DPC-stalled RNA polymerase II. CSA and CSB are indispensable for TC-DPC repair; however, the downstream TC-NER factors UVSSA and XPA are not, a result indicative of a non-canonical TC-NER mechanism. TC-DPC repair functions independently of SPRTN but is mediated by the ubiquitin ligase CRL4CSA and the proteasome. Thus, DPCs in genes are preferentially repaired in a transcription-coupled manner to facilitate unperturbed transcription.
Asunto(s)
ADN Helicasas , Enzimas Reparadoras del ADN , Reparación del ADN , Proteínas de Unión a Poli-ADP-Ribosa , Proteolisis , ARN Polimerasa II , Transcripción Genética , Humanos , Proteínas Portadoras , ADN/metabolismo , ADN/genética , Daño del ADN , ADN Helicasas/metabolismo , ADN Helicasas/genética , Enzimas Reparadoras del ADN/metabolismo , Enzimas Reparadoras del ADN/genética , Proteínas de Unión al ADN/metabolismo , Proteínas de Unión al ADN/genética , Células HEK293 , Proteínas de Unión a Poli-ADP-Ribosa/metabolismo , Proteínas de Unión a Poli-ADP-Ribosa/genética , Complejo de la Endopetidasa Proteasomal/metabolismo , Receptores de Interleucina-17 , ARN Polimerasa II/metabolismo , ARN Polimerasa II/genética , Factores de Transcripción/metabolismo , Factores de Transcripción/genética , Ubiquitina-Proteína Ligasas/metabolismo , Ubiquitina-Proteína Ligasas/genéticaRESUMEN
The therapeutic efficacy of cisplatin and oxaliplatin depends on the balance between the DNA damage induction and the DNA damage response of tumor cells. Based on clinical evidence, oxaliplatin is administered to cisplatin-unresponsive cancers, but the underlying molecular causes for this tumor specificity are not clear. Hence, stratification of patients based on DNA repair profiling is not sufficiently utilized for treatment selection. Using a combination of genetic, transcriptomics and imaging approaches, we identified factors that promote global genome nucleotide excision repair (GG-NER) of DNA-platinum adducts induced by oxaliplatin, but not by cisplatin. We show that oxaliplatin-DNA lesions are a poor substrate for GG-NER initiating factor XPC and that DDB2 and HMGA2 are required for efficient binding of XPC to oxaliplatin lesions and subsequent GG-NER initiation. Loss of DDB2 and HMGA2 therefore leads to hypersensitivity to oxaliplatin but not to cisplatin. As a result, low DDB2 levels in different colon cancer cells are associated with GG-NER deficiency and oxaliplatin hypersensitivity. Finally, we show that colon cancer patients with low DDB2 levels have a better prognosis after oxaliplatin treatment than patients with high DDB2 expression. We therefore propose that DDB2 is a promising predictive marker of oxaliplatin treatment efficiency in colon cancer.
RESUMEN
Transcription-blocking DNA lesions are specifically targeted by transcription-coupled nucleotide excision repair (TC-NER), which removes a broad spectrum of DNA lesions to preserve transcriptional output and thereby cellular homeostasis to counteract aging. TC-NER is initiated by the stalling of RNA polymerase II at DNA lesions, which triggers the assembly of the TC-NER-specific proteins CSA, CSB and UVSSA. CSA, a WD40-repeat containing protein, is the substrate receptor subunit of a cullin-RING ubiquitin ligase complex composed of DDB1, CUL4A/B and RBX1 (CRL4CSA). Although ubiquitination of several TC-NER proteins by CRL4CSA has been reported, it is still unknown how this complex is regulated. To unravel the dynamic molecular interactions and the regulation of this complex, we applied a single-step protein-complex isolation coupled to mass spectrometry analysis and identified DDA1 as a CSA interacting protein. Cryo-EM analysis showed that DDA1 is an integral component of the CRL4CSA complex. Functional analysis revealed that DDA1 coordinates ubiquitination dynamics during TC-NER and is required for efficient turnover and progression of this process.
RESUMEN
The brittle hair syndrome Trichothiodystrophy (TTD) is characterized by variable clinical features, including photosensitivity, ichthyosis, growth retardation, microcephaly, intellectual disability, hypogonadism, and anaemia. TTD-associated mutations typically cause unstable mutant proteins involved in various steps of gene expression, severely reducing steady-state mutant protein levels. However, to date, no such link to instability of gene-expression factors for TTD-associated mutations in MPLKIP/TTDN1 has been established. Here, we present seven additional TTD individuals with MPLKIP mutations from five consanguineous families, with a newly identified MPLKIP variant in one family. By mass spectrometry-based interaction proteomics, we demonstrate that MPLKIP interacts with core splicing factors and the lariat debranching protein DBR1. MPLKIP-deficient primary fibroblasts have reduced steady-state DBR1 protein levels. Using Human Skin Equivalents (HSEs), we observed impaired keratinocyte differentiation associated with compromised splicing and eventually, an imbalanced proteome affecting skin development and, interestingly, also the immune system. Our data show that MPLKIP, through its DBR1 stabilizing role, is implicated in mRNA splicing, which is of particular importance in highly differentiated tissue.
Asunto(s)
Síndromes de Tricotiodistrofia , Humanos , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Consanguinidad , Mutación , Fenotipo , Empalme del ARN , Síndromes de Tricotiodistrofia/genética , Síndromes de Tricotiodistrofia/metabolismoRESUMEN
Transcription-blocking lesions are specifically targeted by transcription-coupled nucleotide excision repair (TC-NER), which prevents DNA damage-induced cellular toxicity and maintains proper transcriptional processes. TC-NER is initiated by the stalling of RNA polymerase II (RNAPII), which triggers the assembly of TC-NER-specific proteins, namely CSB, CSA and UVSSA, which collectively control and drive TC-NER progression. Previous research has revealed molecular functions for these proteins, however, exact mechanisms governing the initiation and regulation of TC-NER, particularly at low UV doses have remained elusive, partly due to technical constraints. In this study, we employ knock-in cell lines designed to target the endogenous CSB gene locus with mClover, a GFP variant. Through live cell imaging, we uncover the intricate molecular dynamics of CSB in response to physiologically relevant UV doses. We showed that the DNA damage-induced association of CSB with chromatin is tightly regulated by the CSA-containing ubiquitin-ligase CRL complex (CRL4CSA). Combining the CSB-mClover knock-in cell line with SILAC-based GFP-mediated complex isolation and mass-spectrometry-based proteomics, revealed novel putative CSB interactors as well as discernible variations in complex composition during distinct stages of TC-NER progression. Our work not only provides molecular insight into TC-NER, but also illustrates the versatility of endogenously tagging fluorescent and affinity tags.
Asunto(s)
Daño del ADN , Reparación del ADN , Línea Celular , Cromatina , Espectrometría de MasasRESUMEN
The SWI/SNF family of ATP-dependent chromatin remodeling complexes is implicated in multiple DNA damage response mechanisms and frequently mutated in cancer. The BAF, PBAF and ncBAF complexes are three major types of SWI/SNF complexes that are functionally distinguished by their exclusive subunits. Accumulating evidence suggests that double-strand breaks (DSBs) in transcriptionally active DNA are preferentially repaired by a dedicated homologous recombination pathway. We show that different BAF, PBAF and ncBAF subunits promote homologous recombination and are rapidly recruited to DSBs in a transcription-dependent manner. The PBAF and ncBAF complexes promote RNA polymerase II eviction near DNA damage to rapidly initiate transcriptional silencing, while the BAF complex helps to maintain this transcriptional silencing. Furthermore, ARID1A-containing BAF complexes promote RNaseH1 and RAD52 recruitment to facilitate R-loop resolution and DNA repair. Our results highlight how multiple SWI/SNF complexes perform different functions to enable DNA repair in the context of actively transcribed genes.
Asunto(s)
Proteínas Cromosómicas no Histona , Estructuras R-Loop , Ensamble y Desensamble de Cromatina/genética , Proteínas Cromosómicas no Histona/metabolismo , ADN , Reparación del ADN/genética , Recombinación Homóloga/genética , HumanosRESUMEN
Transcription-coupled nucleotide excision repair (TC-NER) is an important DNA repair mechanism that protects against the negative effects of transcription-blocking DNA lesions. Hereditary TC-NER deficiencies cause pleiotropic and often severe neurodegenerative and progeroid symptoms. While multiple assays have been developed to determine TC-NER activity for clinical and research purposes, monitoring TC-NER is hampered by the low frequency of repair events occurring in transcribed DNA. 'Recovery of RNA Synthesis' is widely used as indirect TC-NER assay based on the notion that lesion-blocked transcription only resumes after successful TC-NER. Here, we show that measuring novel synthesis of a protein after its compound-induced degradation prior to DNA damage induction is an equally effective but more versatile manner to indirectly monitor DNA repair activity in transcribed genes. This 'Recovery of Protein Synthesis' (RPS) assay can be adapted to various degradable proteins and readouts, including imaging and immunoblotting. Moreover, RPS allows real-time monitoring of TC-NER activity in various living cells types and even in differentiated tissues of living organisms. To illustrate its utility, we show that DNA repair in transcribed genes declines in aging muscle tissue of C. elegans. Therefore, the RPS assay constitutes an important novel clinical and research tool to investigate transcription-coupled DNA repair.
Asunto(s)
Caenorhabditis elegans , Reparación del ADN , Biosíntesis de Proteínas , Transcripción Genética , Animales , Caenorhabditis elegans/fisiología , ADN/metabolismo , Daño del ADN , Envejecimiento/metabolismo , Músculos/metabolismoRESUMEN
R-loops are RNA-DNA-hybrid-containing nucleic acids with important cellular roles. Deregulation of R-loop dynamics can lead to DNA damage and genome instability1, which has been linked to the action of endonucleases such as XPG2-4. However, the mechanisms and cellular consequences of such processing have remained unclear. Here we identify a new population of RNA-DNA hybrids in the cytoplasm that are R-loop-processing products. When nuclear R-loops were perturbed by depleting the RNA-DNA helicase senataxin (SETX) or the breast cancer gene BRCA1 (refs. 5-7), we observed XPG- and XPF-dependent cytoplasmic hybrid formation. We identify their source as a subset of stable, overlapping nuclear hybrids with a specific nucleotide signature. Cytoplasmic hybrids bind to the pattern recognition receptors cGAS and TLR3 (ref. 8), activating IRF3 and inducing apoptosis. Excised hybrids and an R-loop-induced innate immune response were also observed in SETX-mutated cells from patients with ataxia oculomotor apraxia type 2 (ref. 9) and in BRCA1-mutated cancer cells10. These findings establish RNA-DNA hybrids as immunogenic species that aberrantly accumulate in the cytoplasm after R-loop processing, linking R-loop accumulation to cell death through the innate immune response. Aberrant R-loop processing and subsequent innate immune activation may contribute to many diseases, such as neurodegeneration and cancer.
Asunto(s)
Citoplasma , ADN , Reconocimiento de Inmunidad Innata , Ácidos Nucleicos Heterodúplex , Estructuras R-Loop , ARN , Humanos , Apoptosis , Citoplasma/inmunología , Citoplasma/metabolismo , ADN/química , ADN/inmunología , ADN Helicasas/genética , ADN Helicasas/metabolismo , Genes BRCA1 , Enzimas Multifuncionales/genética , Enzimas Multifuncionales/metabolismo , Mutación , Neoplasias , Ácidos Nucleicos Heterodúplex/química , Ácidos Nucleicos Heterodúplex/inmunología , Estructuras R-Loop/inmunología , ARN/química , ARN/inmunología , ARN Helicasas/genética , ARN Helicasas/metabolismo , Ataxias Espinocerebelosas/genéticaRESUMEN
Cockayne syndrome is a rare inherited DNA repair multisystemic disorder. Here, we aim to raise awareness of the phenotypic resemblances between Cockayne syndrome and the neurodevelopmental disorder caused by pathogenic variants in MORC2, a gene also involved in DNA repair. Using exome sequencing, we identified a de novo pathogenic variant in MORC2 in our patient. Our patient's phenotype was characterized by multiple features evocative of Cockayne syndrome. Based on our patient's phenotype, in addition to the phenotypic description of patients with pathogenic variants in MORC2 reported in the literature, we suggest that pathogenic variants in this gene are associated with a Cockayne-like phenotype.
Asunto(s)
Síndrome de Cockayne , Trastornos del Neurodesarrollo , Humanos , Síndrome de Cockayne/genética , Fenotipo , Trastornos del Neurodesarrollo/genética , Secuenciación del Exoma , Factores de Transcripción/genéticaRESUMEN
Nucleotide excision repair (NER) counteracts the onset of cancer and aging by removing helix-distorting DNA lesions via a "cut-and-patch"-type reaction. The regulatory mechanisms that drive NER through its successive damage recognition, verification, incision, and gap restoration reaction steps remain elusive. Here, we show that the RAD5-related translocase HLTF facilitates repair through active eviction of incised damaged DNA together with associated repair proteins. Our data show a dual-incision-dependent recruitment of HLTF to the NER incision complex, which is mediated by HLTF's HIRAN domain that binds 3'-OH single-stranded DNA ends. HLTF's translocase motor subsequently promotes the dissociation of the stably damage-bound incision complex together with the incised oligonucleotide, allowing for an efficient PCNA loading and initiation of repair synthesis. Our findings uncover HLTF as an important NER factor that actively evicts DNA damage, thereby providing additional quality control by coordinating the transition between the excision and DNA synthesis steps to safeguard genome integrity.
Asunto(s)
Reparación del ADN , Proteínas de Unión al ADN , ADN/genética , ADN/metabolismo , Daño del ADN , Replicación del ADN , Proteínas de Unión al ADN/genéticaRESUMEN
The XPG/ERCC5 endonuclease was originally identified as the causative gene for Xeroderma Pigmentosum complementation group G. Ever since its discovery, in depth biochemical, structural and cell biological studies have provided detailed mechanistic insight into its function in excising DNA damage in nucleotide excision repair, together with the ERCC1-XPF endonuclease. In recent years, it has become evident that XPG has additional important roles in genome maintenance that are independent of its function in NER, as XPG has been implicated in protecting replication forks by promoting homologous recombination as well as in resolving R-loops. Here, we provide an overview of the multitasking of XPG in genome maintenance, by describing in detail how its activity in NER is regulated and the evidence that points to important functions outside of NER. Furthermore, we present the various disease phenotypes associated with inherited XPG deficiency and discuss current ideas on how XPG deficiency leads to these different types of disease.
Asunto(s)
Proteínas de Unión al ADN/genética , Endonucleasas/genética , Genoma/genética , Proteínas Nucleares/genética , Factores de Transcripción/genética , Animales , Reparación del ADN/genética , Replicación del ADN/genética , Humanos , Xerodermia Pigmentosa/genéticaRESUMEN
UV-DDB, consisting of subunits DDB1 and DDB2, recognizes UV-induced photoproducts during global genome nucleotide excision repair (GG-NER). We recently demonstrated a noncanonical role of UV-DDB in stimulating base excision repair (BER) which raised several questions about the timing of UV-DDB arrival at 8-oxoguanine (8-oxoG), and the dependency of UV-DDB on the recruitment of downstream BER and NER proteins. Using two different approaches to introduce 8-oxoG in cells, we show that DDB2 is recruited to 8-oxoG immediately after damage and colocalizes with 8-oxoG glycosylase (OGG1) at sites of repair. 8-oxoG removal and OGG1 recruitment is significantly reduced in the absence of DDB2. NER proteins, XPA and XPC, also accumulate at 8-oxoG. While XPC recruitment is dependent on DDB2, XPA recruitment is DDB2-independent and transcription-coupled. Finally, DDB2 accumulation at 8-oxoG induces local chromatin unfolding. We propose that DDB2-mediated chromatin decompaction facilitates the recruitment of downstream BER proteins to 8-oxoG lesions.
Asunto(s)
Reparación del ADN , Proteínas de Unión al ADN/metabolismo , Guanina/análogos & derivados , Línea Celular Tumoral , Cromatina/metabolismo , Ensamble y Desensamble de Cromatina , Daño del ADN/efectos de la radiación , ADN Glicosilasas/metabolismo , Proteínas de Unión al ADN/genética , Técnicas de Silenciamiento del Gen , Técnicas de Inactivación de Genes , Guanina/metabolismo , Guanina/efectos de la radiación , Células HEK293 , Humanos , Rayos Ultravioleta/efectos adversos , Proteína de la Xerodermia Pigmentosa del Grupo A/genética , Proteína de la Xerodermia Pigmentosa del Grupo A/metabolismoRESUMEN
The 10-subunit TFIIH complex is vital to transcription and nucleotide excision repair. Hereditary mutations in its smallest subunit, TTDA/GTF2H5, cause a photosensitive form of the rare developmental disorder trichothiodystrophy. Some trichothiodystrophy features are thought to be caused by subtle transcription or gene expression defects. TTDA/GTF2H5 knockout mice are not viable, making it difficult to investigate TTDA/GTF2H5 in vivo function. Here we show that deficiency of C. elegans TTDA ortholog GTF-2H5 is, however, compatible with life, in contrast to depletion of other TFIIH subunits. GTF-2H5 promotes TFIIH stability in multiple tissues and is indispensable for nucleotide excision repair, in which it facilitates recruitment of TFIIH to DNA damage. Strikingly, when transcription is challenged, gtf-2H5 embryos die due to the intrinsic TFIIH fragility in absence of GTF-2H5. These results support the idea that TTDA/GTF2H5 mutations cause transcription impairment underlying trichothiodystrophy and establish C. elegans as model for studying pathogenesis of this disease.
Asunto(s)
Proteínas de Caenorhabditis elegans/genética , Caenorhabditis elegans/fisiología , Reparación del ADN/genética , ADN de Helmintos/fisiología , Factores de Transcripción/genética , Animales , Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Factores de Transcripción/metabolismoRESUMEN
BACKGROUND: Cell-culture-derived influenza vaccines may enable a closer antigenic match to circulating strains of influenza virus by avoiding egg-adapted mutations. METHODS: We evaluated the efficacy of a cell-culture-derived quadrivalent inactivated influenza vaccine (IIV4c) using a Madin-Darby canine kidney cell line in children and adolescents 2 to less than 18 years of age. During three influenza seasons, participants from eight countries were enrolled in an observer-blinded, randomized clinical trial comparing IIV4c with a noninfluenza vaccine (meningococcal ACWY). All the participants received a dose of a trial vaccine. Children 2 to less than 9 years of age without previous influenza vaccination who were assigned to the IIV4c group received a second dose on day 29; their counterparts who were assigned to the comparator group received placebo. Participants were followed for at least 180 days for efficacy and safety. The presence of influenza virus in nasopharyngeal swabs from participants with influenza-like illness was confirmed by reverse-transcriptase-polymerase-chain-reaction assay and viral culture. A Cox proportional-hazards model was used to evaluate the efficacy of IIV4c as measured by the first occurrence of laboratory-confirmed type A or B influenza (primary end point). RESULTS: Between 2017 and 2019, a total of 4514 participants were randomly assigned to receive IIV4c or the meningococcal ACWY vaccine. Laboratory-confirmed influenza occurred in 175 of 2257 participants (7.8%) in the IIV4c group and in 364 of 2252 participants (16.2%) in the comparator group, and the efficacy of IIV4c was 54.6% (95% confidence interval [CI], 45.7 to 62.1). Efficacy was 80.7% (95% CI, 69.2 to 87.9) against influenza A/H1N1, 42.1% (95% CI, 20.3 to 57.9) against influenza A/H3N2, and 47.6% (95% CI, 31.4 to 60.0) against influenza B. IIV4c showed consistent vaccine efficacy in subgroups according to age, sex, race, and previous influenza vaccination. The incidences of adverse events were similar in the IIV4c group and the comparator group. CONCLUSIONS: IIV4c provided protection against influenza in healthy children and adolescents across seasons, regardless of previous influenza vaccination. (Funded by Seqirus; EudraCT number, 2016-002883-15; ClinicalTrials.gov number, NCT03165617.).