RESUMEN
The genome engineering capability of the CRISPR/Cas system depends on the DNA repair machinery to generate the final outcome. Several genes can have an impact on mutations created, but their exact function and contribution to the result of the repair are not completely characterised. This lack of knowledge has limited the ability to comprehend and regulate the editing outcomes. Here, we measure how the absence of 21 repair genes changes the mutation outcomes of Cas9-generated cuts at 2,812 synthetic target sequences in mouse embryonic stem cells. Absence of key non-homologous end joining genes Lig4, Xrcc4, and Xlf abolished small insertions and deletions, while disabling key microhomology-mediated repair genes Nbn and Polq reduced frequency of longer deletions. Complex alleles of combined insertion and deletions were preferentially generated in the absence of Xrcc6. We further discover finer structure in the outcome frequency changes for single nucleotide insertions and deletions between large microhomologies that are differentially modulated by the knockouts. We use the knowledge of the reproducible variation across repair milieus to build predictive models of Cas9 editing results that outperform the current standards. This work improves our understanding of DNA repair gene function, and provides avenues for more precise modulation of CRISPR/Cas9-generated mutations.
RESUMEN
Patients with chronic obstructive pulmonary disease (COPD) are still waiting for curative treatments. Considering its environmental cause, we hypothesized that COPD will be associated with altered epigenetic signaling in lung cells. We generated genome-wide DNA methylation maps at single CpG resolution of primary human lung fibroblasts (HLFs) across COPD stages. We show that the epigenetic landscape is changed early in COPD, with DNA methylation changes occurring predominantly in regulatory regions. RNA sequencing of matched fibroblasts demonstrated dysregulation of genes involved in proliferation, DNA repair, and extracellular matrix organization. Data integration identified 110 candidate regulators of disease phenotypes that were linked to fibroblast repair processes using phenotypic screens. Our study provides high-resolution multi-omic maps of HLFs across COPD stages. We reveal novel transcriptomic and epigenetic signatures associated with COPD onset and progression and identify new candidate regulators involved in the pathogenesis of chronic lung diseases. The presence of various epigenetic factors among the candidates demonstrates that epigenetic regulation in COPD is an exciting research field that holds promise for novel therapeutic avenues for patients.
Asunto(s)
Enfermedad Pulmonar Obstructiva Crónica , Transcriptoma , Humanos , Epigénesis Genética , Enfermedad Pulmonar Obstructiva Crónica/genética , Enfermedad Pulmonar Obstructiva Crónica/patología , Pulmón/patología , Perfilación de la Expresión Génica , Metilación de ADNRESUMEN
BACKGROUND: Synthetic lethality describes a genetic interaction between two perturbations, leading to cell death, whereas neither event alone has a significant effect on cell viability. This concept can be exploited to specifically target tumor cells. CRISPR viability screens have been widely employed to identify cancer vulnerabilities. However, an approach to systematically infer genetic interactions from viability screens is missing. METHODS: Here we describe PAn-canceR Inferred Synthetic lethalities (PARIS), a machine learning approach to identify cancer vulnerabilities. PARIS predicts synthetic lethal (SL) interactions by combining CRISPR viability screens with genomics and transcriptomics data across hundreds of cancer cell lines profiled within the Cancer Dependency Map. RESULTS: Using PARIS, we predicted 15 high confidence SL interactions within 549 DNA damage repair (DDR) genes. We show experimental validation of an SL interaction between the tumor suppressor CDKN2A, thymidine phosphorylase (TYMP) and the thymidylate synthase (TYMS), which may allow stratifying patients for treatment with TYMS inhibitors. Using genome-wide mapping of SL interactions for DDR genes, we unraveled a dependency between the aldehyde dehydrogenase ALDH2 and the BRCA-interacting protein BRIP1. Our results suggest BRIP1 as a potential therapeutic target in ~ 30% of all tumors, which express low levels of ALDH2. CONCLUSIONS: PARIS is an unbiased, scalable and easy to adapt platform to identify SL interactions that should aid in improving cancer therapy with increased availability of cancer genomics data.
Asunto(s)
Biología Computacional/métodos , Aprendizaje Automático , Modelos Biológicos , Neoplasias/etiología , Mutaciones Letales Sintéticas , Línea Celular Tumoral , Susceptibilidad a Enfermedades , Perfilación de la Expresión Génica/métodos , Predisposición Genética a la Enfermedad , Genómica/métodos , Humanos , Neoplasias/metabolismoRESUMEN
Double-strand breaks (DSBs) are the most toxic type of DNA lesions. Cells repair these lesions using either end protection- or end resection-coupled mechanisms. To study DSB repair choice, we present the Color Assay Tracing-Repair (CAT-R) to simultaneously quantify DSB repair via end protection and end resection pathways. CAT-R introduces DSBs using CRISPR/Cas9 in a tandem fluorescent reporter, whose repair distinguishes small insertions/deletions from large deletions. We demonstrate CAT-R applications in chemical and genetic screens. First, we evaluate 21 compounds currently in clinical trials which target the DNA damage response. Second, we examine how 417 factors involved in DNA damage response influence the choice between end protection and end resection. Finally, we show that impairing nucleotide excision repair favors error-free repair, providing an alternative way for improving CRISPR/Cas9-based knock-ins. CAT-R is a high-throughput, versatile assay to assess DSB repair choice, which facilitates comprehensive studies of DNA repair and drug efficiency testing.
Asunto(s)
Sistemas CRISPR-Cas , Repeticiones Palindrómicas Cortas Agrupadas y Regularmente Espaciadas , Roturas del ADN de Doble Cadena , Reparación del ADN , Proteínas de la Ataxia Telangiectasia Mutada/genética , Ciclo Celular , Supervivencia Celular , Daño del ADN , Reparación del ADN por Unión de Extremidades , Evaluación Preclínica de Medicamentos , Técnicas de Inactivación de Genes , Células HEK293 , Humanos , Poli(ADP-Ribosa) Polimerasa-1/genéticaRESUMEN
TP53 deficiency is the most common alteration in cancer; however, this alone is typically insufficient to drive tumorigenesis. To identify genes promoting tumorigenesis in combination with TP53 deficiency, we perform genome-wide CRISPR-Cas9 knockout screens coupled with proliferation and transformation assays in isogenic cell lines. Loss of several known tumor suppressors enhances cellular proliferation and transformation. Loss of neddylation pathway genes promotes uncontrolled proliferation exclusively in TP53-deficient cells. Combined loss of CUL3 and TP53 activates an oncogenic transcriptional program governed by the nuclear factor κB (NF-κB), AP-1, and transforming growth factor ß (TGF-ß) pathways. This program maintains persistent cellular proliferation, induces partial epithelial to mesenchymal transition, and increases DNA damage, genomic instability, and chromosomal rearrangements. Our findings reveal CUL3 loss as a key event stimulating persistent proliferation in TP53-deficient cells. These findings may be clinically relevant, since TP53-CUL3-deficient cells are highly sensitive to ataxia telangiectasia mutated (ATM) inhibition, exposing a vulnerability that could be exploited for cancer treatment.
Asunto(s)
Proteínas Cullin/genética , Proteína p53 Supresora de Tumor/genética , Proteínas de la Ataxia Telangiectasia Mutada/antagonistas & inhibidores , Proteínas de la Ataxia Telangiectasia Mutada/genética , Proteínas de la Ataxia Telangiectasia Mutada/metabolismo , Carcinogénesis/genética , Línea Celular , Línea Celular Tumoral , Proliferación Celular/fisiología , Proteínas Cullin/metabolismo , Transición Epitelial-Mesenquimal , Estudio de Asociación del Genoma Completo , Inestabilidad Genómica , Humanos , FN-kappa B/metabolismo , Epitelio Pigmentado de la Retina/citología , Factor de Crecimiento Transformador beta/metabolismo , Proteína p53 Supresora de Tumor/deficiencia , Proteína p53 Supresora de Tumor/metabolismoRESUMEN
Arrayed CRISPR-based screens emerge as a powerful alternative to pooled screens making it possible to investigate a wide range of cellular phenotypes that are typically not amenable to pooled screens. Here, we describe a solid-phase transfection platform that enables CRISPR-based genetic screens in arrayed format with flexible readouts. We demonstrate efficient gene knockout upon delivery of guide RNAs and Cas9/guide RNA ribonucleoprotein complexes into untransformed and cancer cell lines. In addition, we provide evidence that our platform can be easily adapted to high-throughput screens and we use this approach to study oncogene addiction in tumor cells. Finally demonstrating that the human primary cells can also be edited using this method, we pave the way for rapid testing of potential targeted therapies.
Asunto(s)
Edición Génica/instrumentación , Neoplasias/genética , ARN Guía de Kinetoplastida/farmacología , Sistemas CRISPR-Cas , Línea Celular Tumoral , Predisposición Genética a la Enfermedad , Ensayos Analíticos de Alto Rendimiento , Humanos , Fenotipo , TransfecciónRESUMEN
Aneuploidy is found in most solid tumours, but it remains unclear whether it is the cause or the consequence of tumorigenesis. Using Plk4 overexpression (PLK4OE) during epidermal development, we assess the impact of centrosome amplification and aneuploidy on skin development and tumorigenesis. PLK4OE in the developing epidermis induced centrosome amplification and multipolar divisions, leading to p53 stabilization and apoptosis of epidermal progenitors. The resulting delayed epidermal stratification led to skin barrier defects. Plk4 transgene expression was shut down postnatally in the surviving mice and PLK4OE mice never developed skin tumours. Concomitant PLK4OE and p53 deletion (PLK4OE/p53cKO) rescued the differentiation defects, but did not prevent the apoptosis of PLK4OE cells. Remarkably, the short-term presence of cells with supernumerary centrosomes in PLK4OE/p53cKO mice was sufficient to generate aneuploidy in the adult epidermis and triggered spontaneous skin cancers with complete penetrance. These results reveal that aneuploidy induced by transient centrosome amplification can accelerate tumorigenesis in p53-deficient cells.
Asunto(s)
Transformación Celular Neoplásica/metabolismo , Centrosoma/metabolismo , Epidermis/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Neoplasias Cutáneas/patología , Proteína p53 Supresora de Tumor/metabolismo , Animales , Apoptosis/genética , Transformación Celular Neoplásica/genética , Ratones , Proteínas Serina-Treonina Quinasas/genética , Neoplasias Cutáneas/genética , Proteína p53 Supresora de Tumor/deficienciaRESUMEN
Claspin is a mediator of the ATR-dependent DNA replication checkpoint in human cells and also promotes DNA replication fork progression and stability. Though Claspin has been shown to bind DNA and co-immunoprecipitate with other replication fork-associated proteins, the specific protein-protein and protein-DNA interactions that are important for Claspin function are not known. We therefore purified several domains of human Claspin and then tested for direct interactions of these fragments with several replication fork-associated proteins and with DNA. Our data show that the N terminus of Claspin binds to the replicative helicase co-factor Cdc45, the Timeless protein and a branched, replication fork-like DNA structure. In contrast, the C terminus of Claspin associates with DNA polymerase epsilon and Rad17-Replication Factor C (RFC). We conclude that multiple protein-DNA and protein-protein interactions may be important for Claspin function during DNA replication and DNA replication checkpoint signaling.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/química , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas de Ciclo Celular/química , Proteínas de Ciclo Celular/metabolismo , Línea Celular Tumoral , ADN/química , ADN/metabolismo , ADN Polimerasa II/química , ADN Polimerasa II/metabolismo , Replicación del ADN , Humanos , Péptidos y Proteínas de Señalización Intracelular/química , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Unión Proteica , Dominios y Motivos de Interacción de Proteínas , Proteína de Replicación C/química , Proteína de Replicación C/metabolismo , Transducción de SeñalRESUMEN
ATR (ATM and Rad3-related) initiates a DNA damage signaling pathway in human cells upon DNA damage induced by UV and UV-mimetic agents and in response to inhibition of DNA replication. Genetic data with human cells and in vitro data with Xenopus egg extracts have led to the conclusion that the kinase activity of ATR toward the signal-transducing kinase Chk1 depends on the mediator protein Claspin. Here we have reconstituted a Claspin-mediated checkpoint system with purified human proteins. We find that the ATR-dependent phosphorylation of Chk1, but not p53, is strongly stimulated by Claspin. Similarly, DNA containing bulky base adducts stimulates ATR kinase activity, and Claspin acts synergistically with damaged DNA to increase phosphorylation of Chk1 by ATR. Mutations in putative phosphorylation sites in the Chk1-binding domain of Claspin abolish its ability to mediate ATR phosphorylation of Chk1. We also find that a fragment of Claspin containing the Chk1-binding domain together with a domain conserved in the yeast Mrc1 orthologs of Claspin is sufficient for its mediator activity. This in vitro system recapitulates essential components of the genetically defined ATR-signaling pathway.