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Plasmodium falciparum reticulocyte-binding protein homolog 5 (RH5) is the most advanced blood-stage malaria vaccine candidate and is being evaluated for efficacy in endemic regions, emphasizing the need to study the underlying antibody response to RH5 during natural infection, which could augment or counteract responses to vaccination. Here, we found that RH5-reactive B cells were rare, and circulating immunoglobulin G (IgG) responses to RH5 were short-lived in malaria-exposed Malian individuals, despite repeated infections over multiple years. RH5-specific monoclonal antibodies isolated from eight malaria-exposed individuals mostly targeted non-neutralizing epitopes, in contrast to antibodies isolated from five RH5-vaccinated, malaria-naive UK individuals. However, MAD8-151 and MAD8-502, isolated from two malaria-exposed Malian individuals, were among the most potent neutralizers out of 186 antibodies from both cohorts and targeted the same epitopes as the most potent vaccine-induced antibodies. These results suggest that natural malaria infection may boost RH5-vaccine-induced responses and provide a clear strategy for the development of next-generation RH5 vaccines.
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The highly conserved and essential Plasmodium falciparum reticulocyte-binding protein homolog 5 (PfRH5) has emerged as the leading target for vaccines against the disease-causing blood stage of malaria. However, the features of the human vaccine-induced antibody response that confer highly potent inhibition of malaria parasite invasion into red blood cells are not well defined. Here, we characterize 236 human IgG monoclonal antibodies, derived from 15 donors, induced by the most advanced PfRH5 vaccine. We define the antigenic landscape of this molecule and establish that epitope specificity, antibody association rate, and intra-PfRH5 antibody interactions are key determinants of functional anti-parasitic potency. In addition, we identify a germline IgG gene combination that results in an exceptionally potent class of antibody and demonstrate its prophylactic potential to protect against P. falciparum parasite challenge in vivo. This comprehensive dataset provides a framework to guide rational design of next-generation vaccines and prophylactic antibodies to protect against blood-stage malaria.
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RNA sequencing in situ allows for whole-transcriptome characterization at high resolution, while retaining spatial information. These data present an analytical challenge for bioinformatics-how to leverage spatial information effectively? Properties of data with a spatial dimension require special handling, which necessitate a different set of statistical and inferential considerations when compared to non-spatial data. The geographical sciences primarily use spatial data and have developed methods to analye them. Here we discuss the challenges associated with spatial analysis and examine how we can take advantage of practice from the geographical sciences to realize the full potential of spatial information in transcriptomic datasets.
Assuntos
Análise de Dados , Análise Espacial , Transcriptoma , Biologia Computacional , Perfilação da Expressão Gênica , Transcriptoma/genéticaRESUMO
Germinal centers (GCs) form in lymph nodes after immunization or infection to facilitate antibody affinity maturation and memory and plasma cell (PC) development. PC differentiation is thought to involve stringent selection for GC B cells expressing the highest-affinity antigen receptors, but how this plays out during complex polyclonal responses is unclear. We combine temporal lineage tracing with antibody characterization to gain a snapshot of PCs developing during influenza infection. GCs co-mature B cell clones with antibody affinities spanning multiple orders of magnitude; however, each generates PCs with similar efficiencies, including weak binders. Within lineages, PC selection is not restricted to variants with the highest-affinity antibodies. Differentiation is commonly associated with proliferative expansion to produce "nodes" of identical PCs. Immunization-induced GCs generate fewer PCs but still of low- and high-antibody affinities. We propose that generating low-affinity antibody PCs reflects an evolutionary compromise to facilitate diverse serum antibody responses.
Assuntos
Afinidade de Anticorpos , Linfócitos B , Centro Germinativo , Plasmócitos , Formação de Anticorpos , Linfócitos B/citologia , Linfócitos B/imunologia , Linfonodos , Linhagem Celular , Humanos , Animais , Camundongos , Cricetinae , Vírus da Influenza A/imunologia , Diferenciação CelularRESUMO
The T cell receptor (TCR) expressed by T lymphocytes initiates protective immune responses to pathogens and tumors. To explore the structural basis of how TCR signaling is initiated when the receptor binds to peptide-loaded major histocompatibility complex (pMHC) molecules, we used cryogenic electron microscopy to determine the structure of a tumor-reactive TCRαß/CD3δγε2ζ2 complex bound to a melanoma-specific human class I pMHC at 3.08 Å resolution. The antigen-bound complex comprises 11 subunits stabilized by multivalent interactions across three structural layers, with clustered membrane-proximal cystines stabilizing the CD3-εδ and CD3-εγ heterodimers. Extra density sandwiched between transmembrane helices reveals the involvement of sterol lipids in TCR assembly. The geometry of the pMHC/TCR complex suggests that efficient TCR scanning of pMHC requires accurate pre-positioning of T cell and antigen-presenting cell membranes. Comparisons of the ligand-bound and unliganded receptors, along with molecular dynamics simulations, indicate that TCRs can be triggered in the absence of spontaneous structural rearrangements.
Assuntos
Neoplasias , Receptores de Antígenos de Linfócitos T , Humanos , Complexo Principal de Histocompatibilidade , Peptídeos/química , Ligação Proteica , Receptores de Antígenos de Linfócitos T/metabolismo , Receptores de Antígenos de Linfócitos T alfa-beta/química , Receptores de Antígenos de Linfócitos T alfa-beta/metabolismoRESUMO
Since the first reports of a novel severe acute respiratory syndrome (SARS)-like coronavirus in December 2019 in Wuhan, China, there has been intense interest in understanding how severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in the human population. Recent debate has coalesced around two competing ideas: a "laboratory escape" scenario and zoonotic emergence. Here, we critically review the current scientific evidence that may help clarify the origin of SARS-CoV-2.
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SARS-CoV-2/fisiologia , Animais , Evolução Biológica , COVID-19/virologia , Humanos , Laboratórios , SARS-CoV-2/genética , Zoonoses/virologiaRESUMO
Gene expression by RNA polymerase II (RNAPII) is tightly controlled by cyclin-dependent kinases (CDKs) at discrete checkpoints during the transcription cycle. The pausing checkpoint following transcription initiation is primarily controlled by CDK9. We discovered that CDK9-mediated, RNAPII-driven transcription is functionally opposed by a protein phosphatase 2A (PP2A) complex that is recruited to transcription sites by the Integrator complex subunit INTS6. PP2A dynamically antagonizes phosphorylation of key CDK9 substrates including DSIF and RNAPII-CTD. Loss of INTS6 results in resistance to tumor cell death mediated by CDK9 inhibition, decreased turnover of CDK9 phospho-substrates, and amplification of acute oncogenic transcriptional responses. Pharmacological PP2A activation synergizes with CDK9 inhibition to kill both leukemic and solid tumor cells, providing therapeutic benefit in vivo. These data demonstrate that fine control of gene expression relies on the balance between kinase and phosphatase activity throughout the transcription cycle, a process dysregulated in cancer that can be exploited therapeutically.
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Quinase 9 Dependente de Ciclina/metabolismo , Terapia de Alvo Molecular , Neoplasias/tratamento farmacológico , Neoplasias/genética , Proteína Fosfatase 2/metabolismo , Proteínas de Ligação a RNA/metabolismo , Transcrição Gênica , Proteínas Supressoras de Tumor/metabolismo , Animais , Linhagem Celular Tumoral , Quinase 9 Dependente de Ciclina/antagonistas & inibidores , Resistencia a Medicamentos Antineoplásicos/genética , Regulação Neoplásica da Expressão Gênica , Humanos , Camundongos Endogâmicos NOD , Fosforilação , Ligação Proteica , RNA Polimerase II/química , RNA Polimerase II/metabolismo , Especificidade por SubstratoRESUMO
Although mutations in DNA are the best-studied source of neoantigens that determine response to immune checkpoint blockade, alterations in RNA splicing within cancer cells could similarly result in neoepitope production. However, the endogenous antigenicity and clinical potential of such splicing-derived epitopes have not been tested. Here, we demonstrate that pharmacologic modulation of splicing via specific drug classes generates bona fide neoantigens and elicits anti-tumor immunity, augmenting checkpoint immunotherapy. Splicing modulation inhibited tumor growth and enhanced checkpoint blockade in a manner dependent on host T cells and peptides presented on tumor MHC class I. Splicing modulation induced stereotyped splicing changes across tumor types, altering the MHC I-bound immunopeptidome to yield splicing-derived neoepitopes that trigger an anti-tumor T cell response in vivo. These data definitively identify splicing modulation as an untapped source of immunogenic peptides and provide a means to enhance response to checkpoint blockade that is readily translatable to the clinic.
Assuntos
Neoplasias/genética , Neoplasias/imunologia , Splicing de RNA/genética , Animais , Apresentação de Antígeno/efeitos dos fármacos , Apresentação de Antígeno/imunologia , Antígenos de Neoplasias/metabolismo , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Epitopos/imunologia , Etilenodiaminas/farmacologia , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Hematopoese/efeitos dos fármacos , Hematopoese/genética , Antígenos de Histocompatibilidade Classe I/metabolismo , Humanos , Inibidores de Checkpoint Imunológico/farmacologia , Imunoterapia , Inflamação/patologia , Camundongos Endogâmicos C57BL , Peptídeos/metabolismo , Isoformas de Proteínas/metabolismo , Pirróis/farmacologia , Splicing de RNA/efeitos dos fármacos , Sulfonamidas/farmacologia , Linfócitos T/efeitos dos fármacos , Linfócitos T/imunologiaRESUMO
B cell progenitor acute lymphoblastic leukemia (B-ALL) treatment has been revolutionized by T cell-based immunotherapies-including chimeric antigen receptor T cell therapy (CAR-T) and the bispecific T cell engager therapeutic, blinatumomab-targeting surface glycoprotein CD19. Unfortunately, many patients with B-ALL will fail immunotherapy due to 'antigen escape'-the loss or absence of leukemic CD19 targeted by anti-leukemic T cells. In the present study, we utilized a genome-wide CRISPR-Cas9 screening approach to identify modulators of CD19 abundance on human B-ALL blasts. These studies identified a critical role for the transcriptional activator ZNF143 in CD19 promoter activation. Conversely, the RNA-binding protein, NUDT21, limited expression of CD19 by regulating CD19 messenger RNA polyadenylation and stability. NUDT21 deletion in B-ALL cells increased the expression of CD19 and the sensitivity to CD19-specific CAR-T and blinatumomab. In human B-ALL patients treated with CAR-T and blinatumomab, upregulation of NUDT21 mRNA coincided with CD19 loss at disease relapse. Together, these studies identify new CD19 modulators in human B-ALL.
Assuntos
Linfoma de Burkitt , Linfoma de Células B , Leucemia-Linfoma Linfoblástico de Células Precursoras , Receptores de Antígenos Quiméricos , Antígenos CD19/genética , Antígenos CD19/metabolismo , Fator de Especificidade de Clivagem e Poliadenilação/metabolismo , Humanos , Imunoterapia Adotiva/efeitos adversos , Glicoproteínas de Membrana/metabolismo , Poliadenilação , Leucemia-Linfoma Linfoblástico de Células Precursoras/tratamento farmacológico , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Receptores de Antígenos Quiméricos/metabolismo , Transativadores/metabolismoRESUMO
CD28 and CTLA-4 (CD152) play essential roles in regulating T cell immunity, balancing the activation and inhibition of T cell responses, respectively. Although both receptors share the same ligands, CD80 and CD86, the specific requirement for two distinct ligands remains obscure. In the present study, we demonstrate that, although CTLA-4 targets both CD80 and CD86 for destruction via transendocytosis, this process results in separate fates for CTLA-4 itself. In the presence of CD80, CTLA-4 remained ligand bound, and was ubiquitylated and trafficked via late endosomes and lysosomes. In contrast, in the presence of CD86, CTLA-4 detached in a pH-dependent manner and recycled back to the cell surface to permit further transendocytosis. Furthermore, we identified clinically relevant mutations that cause autoimmune disease, which selectively disrupted CD86 transendocytosis, by affecting either CTLA-4 recycling or CD86 binding. These observations provide a rationale for two distinct ligands and show that defects in CTLA-4-mediated transendocytosis of CD86 are associated with autoimmunity.
Assuntos
Antígenos CD , Antígenos CD28 , Antígenos CD/metabolismo , Antígenos de Diferenciação/metabolismo , Antígeno B7-1 , Antígeno B7-2/genética , Antígenos CD28/metabolismo , Antígeno CTLA-4/genética , Moléculas de Adesão Celular , Ligantes , Ativação LinfocitáriaRESUMO
The Plasmodium falciparum reticulocyte-binding protein homolog 5 (PfRH5) is the leading target for next-generation vaccines against the disease-causing blood-stage of malaria. However, little is known about how human antibodies confer functional immunity against this antigen. We isolated a panel of human monoclonal antibodies (mAbs) against PfRH5 from peripheral blood B cells from vaccinees in the first clinical trial of a PfRH5-based vaccine. We identified a subset of mAbs with neutralizing activity that bind to three distinct sites and another subset of mAbs that are non-functional, or even antagonistic to neutralizing antibodies. We also identify the epitope of a novel group of non-neutralizing antibodies that significantly reduce the speed of red blood cell invasion by the merozoite, thereby potentiating the effect of all neutralizing PfRH5 antibodies as well as synergizing with antibodies targeting other malaria invasion proteins. Our results provide a roadmap for structure-guided vaccine development to maximize antibody efficacy against blood-stage malaria.
Assuntos
Anticorpos Monoclonais/imunologia , Anticorpos Neutralizantes/imunologia , Anticorpos Antiprotozoários/imunologia , Eritrócitos/parasitologia , Vacinas Antimaláricas/imunologia , Malária Falciparum/imunologia , Plasmodium falciparum/imunologia , Adolescente , Adulto , Animais , Sítios de Ligação , Proteínas de Transporte/imunologia , Reações Cruzadas/imunologia , Epitopos/imunologia , Feminino , Células HEK293 , Voluntários Saudáveis , Humanos , Malária Falciparum/parasitologia , Masculino , Merozoítos/fisiologia , Pessoa de Meia-Idade , Plasmodium falciparum/metabolismo , Proteínas de Protozoários/imunologia , Coelhos , Ratos , Ratos Sprague-Dawley , Adulto JovemRESUMO
Antibodies can block immune receptor engagement or trigger the receptor machinery to initiate signaling. We hypothesized that antibody agonists trigger signaling by sterically excluding large receptor-type protein tyrosine phosphatases (RPTPs) such as CD45 from sites of receptor engagement. An agonist targeting the costimulatory receptor CD28 produced signals that depended on antibody immobilization and were sensitive to the sizes of the receptor, the RPTPs, and the antibody itself. Although both the agonist and a non-agonistic anti-CD28 antibody locally excluded CD45, the agonistic antibody was more effective. An anti-PD-1 antibody that bound membrane proximally excluded CD45, triggered Src homology 2 domain-containing phosphatase 2 recruitment, and suppressed systemic lupus erythematosus and delayed-type hypersensitivity in experimental models. Paradoxically, nivolumab and pembrolizumab, anti-PD-1-blocking antibodies used clinically, also excluded CD45 and were agonistic in certain settings. Reducing these agonistic effects using antibody engineering improved PD-1 blockade. These findings establish a framework for developing new and improved therapies for autoimmunity and cancer.
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Proteínas Tirosina Fosfatases , Transdução de Sinais , Proteínas Tirosina Fosfatases/metabolismo , Antígenos CD28 , Receptores ImunológicosRESUMO
Telomere maintenance critically depends on the distinct activities of telomerase, which adds telomeric repeats to solve the end replication problem, and RTEL1, which dismantles DNA secondary structures at telomeres to facilitate replisome progression. Here, we establish that reversed replication forks are a pathological substrate for telomerase and the source of telomere catastrophe in Rtel1-/- cells. Inhibiting telomerase recruitment to telomeres, but not its activity, or blocking replication fork reversal through PARP1 inhibition or depleting UBC13 or ZRANB3 prevents the rapid accumulation of dysfunctional telomeres in RTEL1-deficient cells. In this context, we establish that telomerase binding to reversed replication forks inhibits telomere replication, which can be mimicked by preventing replication fork restart through depletion of RECQ1 or PARG. Our results lead us to propose that telomerase inappropriately binds to and inhibits restart of reversed replication forks within telomeres, which compromises replication and leads to critically short telomeres.
Assuntos
DNA Helicases/genética , Replicação do DNA , Homeostase do Telômero , Animais , Linhagem Celular , Células Cultivadas , DNA Helicases/metabolismo , Glicosídeo Hidrolases/metabolismo , Camundongos , Poli(ADP-Ribose) Polimerase-1/metabolismo , RecQ Helicases/metabolismo , Enzimas de Conjugação de Ubiquitina/metabolismoRESUMO
The cyclic guanosine monophosphate (GMP)-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway plays a pivotal role in innate immune responses to viral infection and inhibition of autoimmunity. Recent studies have suggested that micronuclei formed by genotoxic stress can activate innate immune signaling via the cGAS-STING pathway. Here, we investigated cGAS localization, activation, and downstream signaling from micronuclei induced by ionizing radiation, replication stress, and chromosome segregation errors. Although cGAS localized to ruptured micronuclei via binding to self-DNA, we failed to observe cGAS activation; cGAMP production; downstream phosphorylation of STING, TBK1, or IRF3; nuclear accumulation of IRF3; or expression of interferon-stimulated genes. Failure to activate the cGAS-STING pathway was observed across primary and immortalized cell lines, which retained the ability to activate the cGAS-STING pathway in response to dsDNA or modified vaccinia virus infection. We provide evidence that micronuclei formed by genotoxic insults contain histone-bound self-DNA, which we show is inhibitory to cGAS activation in cells.
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Segregação de Cromossomos , Proteínas de Membrana , Micronúcleos com Defeito Cromossômico , Nucleotídeos Cíclicos , Nucleotidiltransferases , Transdução de Sinais , Nucleotidiltransferases/metabolismo , Nucleotidiltransferases/genética , Humanos , Proteínas de Membrana/metabolismo , Proteínas de Membrana/genética , Micronúcleos com Defeito Cromossômico/efeitos da radiação , Nucleotídeos Cíclicos/metabolismo , Fosforilação , Replicação do DNA/efeitos da radiação , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Serina-Treonina Quinases/genética , Fator Regulador 3 de Interferon/metabolismo , Fator Regulador 3 de Interferon/genética , Imunidade Inata/efeitos da radiação , Dano ao DNA , Células HEK293 , Animais , Radiação Ionizante , Células HeLaRESUMO
G-quadruplexes (G4s) form throughout the genome and influence important cellular processes. Their deregulation can challenge DNA replication fork progression and threaten genome stability. Here, we demonstrate an unexpected role for the double-stranded DNA (dsDNA) translocase helicase-like transcription factor (HLTF) in responding to G4s. We show that HLTF, which is enriched at G4s in the human genome, can directly unfold G4s in vitro and uses this ATP-dependent translocase function to suppress G4 accumulation throughout the cell cycle. Additionally, MSH2 (a component of MutS heterodimers that bind G4s) and HLTF act synergistically to suppress G4 accumulation, restrict alternative lengthening of telomeres, and promote resistance to G4-stabilizing drugs. In a discrete but complementary role, HLTF restrains DNA synthesis when G4s are stabilized by suppressing primase-polymerase (PrimPol)-dependent repriming. Together, the distinct roles of HLTF in the G4 response prevent DNA damage and potentially mutagenic replication to safeguard genome stability.
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DNA Primase , Replicação do DNA , Proteínas de Ligação a DNA , Quadruplex G , Instabilidade Genômica , Proteína 2 Homóloga a MutS , Fatores de Transcrição , Humanos , Fatores de Transcrição/metabolismo , Fatores de Transcrição/genética , Proteínas de Ligação a DNA/metabolismo , Proteínas de Ligação a DNA/genética , Proteína 2 Homóloga a MutS/metabolismo , Proteína 2 Homóloga a MutS/genética , DNA Primase/metabolismo , DNA Primase/genética , Homeostase do Telômero , Dano ao DNA , Células HEK293 , Enzimas Multifuncionais/metabolismo , Enzimas Multifuncionais/genética , DNA Polimerase Dirigida por DNARESUMO
Mutations in the RNA splicing factor gene SF3B1 are common across hematologic and solid cancers and result in widespread alterations in splicing, yet there is currently no therapeutic means to correct this mis-splicing. Here, we utilize synthetic introns uniquely responsive to mutant SF3B1 to identify trans factors required for aberrant mutant SF3B1 splicing activity. This revealed the G-patch domain-containing protein GPATCH8 as required for mutant SF3B1-induced splicing alterations and impaired hematopoiesis. GPATCH8 is involved in quality control of branchpoint selection, interacts with the RNA helicase DHX15, and functionally opposes SURP and G-patch domain containing 1 (SUGP1), a G-patch protein recently implicated in SF3B1-mutant diseases. Silencing of GPATCH8 corrected one-third of mutant SF3B1-dependent splicing defects and was sufficient to improve dysfunctional hematopoiesis in SF3B1-mutant mice and primary human progenitors. These data identify GPATCH8 as a novel splicing factor required for mis-splicing by mutant SF3B1 and highlight the therapeutic impact of correcting aberrant splicing in SF3B1-mutant cancers.
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Neoplasias Hematológicas , Proteínas Musculares , Mutação , Fosfoproteínas , Fatores de Processamento de RNA , Animais , Humanos , Camundongos , RNA Helicases DEAD-box/genética , RNA Helicases DEAD-box/metabolismo , Células HEK293 , Neoplasias Hematológicas/genética , Neoplasias Hematológicas/patologia , Neoplasias Hematológicas/metabolismo , Hematopoese/genética , Íntrons , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , RNA Helicases/genética , RNA Helicases/metabolismo , Splicing de RNA , Fatores de Processamento de RNA/genética , Fatores de Processamento de RNA/metabolismo , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismo , Proteínas Musculares/genética , Proteínas Musculares/metabolismoRESUMO
Innate immune memory is the phenomenon whereby innate immune cells such as monocytes or macrophages undergo functional reprogramming after exposure to microbial components such as lipopolysaccharide (LPS). We apply an integrated epigenomic approach to characterize the molecular events involved in LPS-induced tolerance in a time-dependent manner. Mechanistically, LPS-treated monocytes fail to accumulate active histone marks at promoter and enhancers of genes in the lipid metabolism and phagocytic pathways. Transcriptional inactivity in response to a second LPS exposure in tolerized macrophages is accompanied by failure to deposit active histone marks at promoters of tolerized genes. In contrast, ß-glucan partially reverses the LPS-induced tolerance in vitro. Importantly, ex vivo ß-glucan treatment of monocytes from volunteers with experimental endotoxemia re-instates their capacity for cytokine production. Tolerance is reversed at the level of distal element histone modification and transcriptional reactivation of otherwise unresponsive genes. VIDEO ABSTRACT.
Assuntos
Tolerância Imunológica , Lipopolissacarídeos/imunologia , Macrófagos/imunologia , Monócitos/imunologia , Sepse/imunologia , Transcrição Gênica , beta-Glucanas/imunologia , Diferenciação Celular , Metilação de DNA , Epigenômica , Redes Reguladoras de Genes , Código das Histonas , Humanos , Imunidade Inata , Memória Imunológica , Macrófagos/citologia , Monócitos/citologia , Sepse/genéticaRESUMO
Homologous recombination (HR) is essential for error-free repair of DNA double-strand breaks, perturbed replication forks (RFs), and post-replicative single-stranded DNA (ssDNA) gaps. To initiate HR, the recombination mediator and tumor suppressor protein BRCA2 facilitates nucleation of RAD51 on ssDNA prior to stimulation of RAD51 filament growth by RAD51 paralogs. Although ssDNA binding by BRCA2 has been implicated in RAD51 nucleation, the function of double-stranded DNA (dsDNA) binding by BRCA2 remains unclear. Here, we exploit single-molecule (SM) imaging to visualize BRCA2-mediated RAD51 nucleation in real time using purified proteins. We report that BRCA2 nucleates and stabilizes RAD51 on ssDNA either directly or through an unappreciated diffusion-assisted delivery mechanism involving binding to and sliding along dsDNA, which requires the cooperative action of multiple dsDNA-binding modules in BRCA2. Collectively, our work reveals two distinct mechanisms of BRCA2-dependent RAD51 loading onto ssDNA, which we propose are critical for its diverse functions in maintaining genome stability and cancer suppression.
Assuntos
Proteína BRCA2 , Rad51 Recombinase , Humanos , Proteína BRCA2/genética , Proteína BRCA2/metabolismo , Rad51 Recombinase/genética , Rad51 Recombinase/metabolismo , Proteínas de Ligação a DNA/metabolismo , DNA de Cadeia Simples/genética , DNA/metabolismo , Reparo do DNA , Ligação ProteicaRESUMO
CRISPR-Cas9 is a powerful gene-editing technology; however, off-target activity remains an important consideration for therapeutic applications. We have previously shown that force-stretching DNA induces off-target activity and hypothesized that distortions of the DNA topology in vivo, such as negative DNA supercoiling, could reduce Cas9 specificity. Using single-molecule optical-tweezers, we demonstrate that negative supercoiling λ-DNA induces sequence-specific Cas9 off-target binding at multiple sites, even at low forces. Using an adapted CIRCLE-seq approach, we detect over 10,000 negative-supercoiling-induced Cas9 off-target double-strand breaks genome-wide caused by increased mismatch tolerance. We further demonstrate in vivo that directed local DNA distortion increases off-target activity in cells and that induced off-target events can be detected during Cas9 genome editing. These data demonstrate that Cas9 off-target activity is regulated by DNA topology in vitro and in vivo, suggesting that cellular processes, such as transcription and replication, could induce off-target activity at previously overlooked sites.
Assuntos
Sistemas CRISPR-Cas , Edição de Genes , Genoma , DNA/genética , Pinças ÓpticasRESUMO
Microhomology-mediated end joining (MMEJ) is an intrinsically mutagenic pathway of DNA double-strand break (DSB) repair essential for proliferation of homologous recombination (HR)-deficient tumors. Although targeting MMEJ has emerged as a powerful strategy to eliminate HR-deficient (HRD) cancers, this is limited by an incomplete understanding of the mechanism and factors required for MMEJ repair. Here, we identify the APE2 nuclease as an MMEJ effector. We show that loss of APE2 inhibits MMEJ at deprotected telomeres and at intra-chromosomal DSBs and is epistatic with Pol Theta for MMEJ activity. Mechanistically, we demonstrate that APE2 possesses intrinsic flap-cleaving activity, that its MMEJ function in cells depends on its nuclease activity, and further identify an uncharacterized domain required for its recruitment to DSBs. We conclude that this previously unappreciated role of APE2 in MMEJ contributes to the addiction of HRD cells to APE2, which could be exploited in the treatment of cancer.