RESUMEN

BACKGROUND: Cisplatin (CDDP) remains a key agent in the treatment of muscle-infiltrating bladder carcinoma (MIBC). However, a proportion of MIBC patients do not respond to chemotherapy, which may be caused by the increased repair of CDDP-induced DNA damage. The purpose of this study was to explore the prognostic value of proteins involved in nucleotide excision repair (NER) and translesion DNA synthesis (TLS) in MIBC patients. METHODS: This is a retrospective analysis of 86 MIBC patients. The XPA, XPF, XPG, ERCC1, POLI, POLH and REV3L proteins were stained in primary bladder tumors and their levels were analyzed both in the total cohort and in a subgroup with metastatic urothelial carcinoma (mUC) that received gemcitabine and CDDP as a first-line therapy. Both cohorts were divided by percentage of cancer cells stained positive for each protein into subgroups with high and low expression. In the same manner, the combined expression of NER (XPA + ERCC1 + XPF + XPG) and TLS (POLI + POLH + REV3L), as the whole pathways, was analyzed. RESULTS: Mortality was 89.5% at the median follow-up of 120.2 months. In the total cohort, patients with tumors stained positive for XPA, XPG and POLI had significantly worse overall survival (OS) compared to those with negative staining [hazard ratio (HR) = 0.60, 0.62 and 0.53, respectively]. Both XPG and POLI were independent prognostic factors in multivariate analyses (MVA). In addition, an increase in NER and TLS pathway expression was significantly associated with worse OS in the total cohort (HR = 0.54 and 0.60, respectively). In the mUC subgroup, high POLI expression was associated with significant deterioration of OS (HR = 0.56) in univariate analyses, and its independent prognostic value was shown in MVA. CONCLUSIONS: Our study showed significant correlations between the tumor expression of XPG and POLI, as well as NER and TLS as the whole pathways, and inferior OS. Hence, they could constitute prognostic biomarkers and potentially promising therapeutic targets in MIBC. However, a prospective trial is required for further validation, thereby overcoming the limitations of this study.

Asunto(s)

Reparación del ADN , Neoplasias de la Vejiga Urinaria , Humanos , Neoplasias de la Vejiga Urinaria/patología , Neoplasias de la Vejiga Urinaria/mortalidad , Neoplasias de la Vejiga Urinaria/genética , Neoplasias de la Vejiga Urinaria/metabolismo , Masculino , Femenino , Anciano , Pronóstico , Persona de Mediana Edad , Estudios Retrospectivos , Anciano de 80 o más Años , Cisplatino/uso terapéutico , Proteínas de Unión al ADN/metabolismo , Proteínas de Unión al ADN/genética , Adulto , Biomarcadores de Tumor/metabolismo , Biomarcadores de Tumor/genética , Endonucleasas/metabolismo , Endonucleasas/genética , Desoxicitidina/análogos & derivados , Desoxicitidina/uso terapéutico , Reparación por Escisión , Síntesis Translesional de ADN

RESUMEN

Pierisin is a DNA-targeting ADP-ribosyltransferase found in cabbage white butterfly (Pieris rapae). Pierisin transfers an ADP-ribosyl moiety to the 2-amino group of the guanine residue in DNA, yielding N2-(ADP-ribos-1-yl)-2'-deoxyguanosine (N2-ADPR-dG). Generally, such chemically modified DNA is recognized as DNA damage and elicits cellular responses, including DNA repair pathways. In Escherichia coli and human cells, it has been experimentally demonstrated that N2-ADPR-dG is a substrate of the nucleotide excision repair system. Although DNA repair machineries can remove most lesions, some unrepaired damages frequently lead to mutagenesis through DNA replication. Replication past the damaged DNA template is called translesion DNA synthesis (TLS). In vitro primer extension experiments have shown that eukaryotic DNA polymerase κ is involved in TLS across N2-ADPR-dG. In many cases, TLS is error-prone and thus a mutagenic process. Indeed, the induction of G:C to T:A and G:C to C:G mutations by N2-ADPR-dG in the hypoxanthine phosphoribosyltransferase gene mutation assay with Chinese hamster cells and supF shuttle vector plasmids assay using human fibroblasts has been reported. This review provides a detailed overview of DNA repair, TLS and mutagenesis of N2-ADPR-dG induced by cabbage butterfly pierisin-1.

Asunto(s)

Reparación del ADN , ADN , Mutagénesis , Animales , Humanos , ADN/genética , ADP Ribosa Transferasas/genética , ADP Ribosa Transferasas/metabolismo , Daño del ADN , Proteínas de Insectos/genética , Proteínas de Insectos/metabolismo , Mariposas Diurnas/genética , Mariposas Diurnas/enzimología

RESUMEN

Introduction: UV-sensitive syndrome and Cockayne syndrome (CS) are rare autosomal recessive and transcription-coupled nucleotide excision repair disorders with different clinical manifestations, although some types are allelic. Case Presentation: We report on a patient who passed away at 15 years old with a progeroid-like appearance, cachexia, hearing loss, and dental anomalies, which led us to the diagnosis of Cockayne-like progeroid syndromes. Our clinical exome sequencing including all the known genes of progeroid syndromes revealed a homozygous stop-gain variant in the UVSSA gene. Conclusion: Although truncating variants in the UVSSA are known to cause UVsS3, their association with CS has not yet been defined. This case might be the first report of a CS-like phenotype caused by a defective UVSSA.

RESUMEN

INTRODUCTION: Ovarian cancer (OC) poses significant challenges due to its high mortality rate, particularly in advanced stages where symptoms may not be evident. DNA repair mechanisms, including nucleotide excision repair (NER), are crucial in maintaining genomic stability and preventing cancer. This study focuses on exploring the role of two NER-related genes, Xeroderma Pigmentosum Complementation Group C (XPC) and DNA Damage Binding Protein 2 (DDB2), in OC susceptibility. OBJECTIVES: This study aims to investigate the association between variations in two NER-related genes, XPC rs2228001 and DDB2 rs830083, among a cohort of Turkish individuals with OC and control subjects. METHODS: Genotyping of XPC rs2228001 and DDB2 rs830083 was performed on 103 OC patients and 104 control subjects from the Turkish population using the Fast Real-Time 7500 PCR platform from Applied Biosystems. RESULTS: Individuals with the homozygous AA genotype of XPC rs2228001 exhibited a reduced likelihood of developing OC (OR 0.511; 95% CI 0.261 - 1.003; P-value 0.049), whereas those with the CC variant faced an elevated risk (OR = 2.32, 95% CI = 1.75-3.08; P-value 0.035). The presence of the A allele was associated with decreased OC occurrence (P-value = 0.035). Similarly, for DDB2 rs830083, individuals with the homozygous CG genotype had a diminished risk of OC (P-value 0.036), compared to those with the GG polymorphism (OR 1.895; 95% CI 1.033 - 3.476; P-value 0.038). Furthermore, the presence of the C allele was associated with a 1.89-fold decrease in the likelihood of OC. CONCLUSION: These findings shed light on the genetic factors influencing OC susceptibility, emphasizing the importance of DNA repair systems in disease. Further research in larger and more diverse populations is warranted to validate these findings, facilitating precise risk assessment, and potentially guiding tailored treatment strategies for OC patients.

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Ovarian cancer is a serious disease with a high mortality rate, especially in its advanced stages when symptoms are often not obvious. Our cells have mechanisms to repair DNA damage and maintain stability in our genetic material. Two genes involved in one of these repair mechanisms, called nucleotide excision repair (NER), are Xeroderma Pigmentosum Complementation Group C (XPC) and DNA Damage Binding Protein 2 (DDB2). This study investigates how variations in these genes may influence the risk of developing ovarian cancer. Understanding these genetic factors could lead to improved methods for diagnosing and treating this challenging disease.

Asunto(s)

Reparación del ADN , Proteínas de Unión al ADN , Predisposición Genética a la Enfermedad , Neoplasias Ováricas , Polimorfismo de Nucleótido Simple , Humanos , Femenino , Neoplasias Ováricas/genética , Turquía/epidemiología , Persona de Mediana Edad , Reparación del ADN/genética , Proteínas de Unión al ADN/genética , Adulto , Genotipo , Estudios de Casos y Controles , Anciano

RESUMEN

Nucleotide excision repair (NER) is the most universal repair pathway, which removes a wide range of DNA helix-distorting lesions caused by chemical or physical agents. The final steps of this repair process are gap-filling repair synthesis and subsequent ligation. XPA is the central NER scaffolding protein factor and can be involved in post-incision NER stages. Replication machinery is loaded after the first incision of the damaged strand that is performed by the XPF-ERCC1 nuclease forming a damaged 5'-flap processed by the XPG endonuclease. Flap endonuclease I (FEN1) is a critical component of replication machinery and is absolutely indispensable for the maturation of newly synthesized strands. FEN1 also contributes to the long-patch pathway of base excision repair. Here, we use a set of DNA substrates containing a fluorescently labeled 5'-flap and different size gap to analyze possible repair factor-replication factor interactions. Ternary XPA-FEN1-DNA complexes with each tested DNA are detected. Furthermore, we demonstrate XPA-FEN1 complex formation in the absence of DNA due to protein-protein interaction. Functional assays reveal that XPA moderately inhibits FEN1 catalytic activity. Using fluorescently labeled XPA, formation of ternary RPA-XPA-FEN1 complex, where XPA accommodates FEN1 and RPA contacts simultaneously, can be proposed. We discuss possible functional roles of the XPA-FEN1 interaction in NER related DNA resynthesis and/or other DNA metabolic processes where XPA can be involved in the complex with FEN1.

Asunto(s)

Reparación del ADN , Endonucleasas de ADN Solapado , Proteína de la Xerodermia Pigmentosa del Grupo A , Endonucleasas de ADN Solapado/metabolismo , Endonucleasas de ADN Solapado/genética , Humanos , Proteína de la Xerodermia Pigmentosa del Grupo A/metabolismo , Proteína de la Xerodermia Pigmentosa del Grupo A/genética , ADN/metabolismo , Unión Proteica , Reparación por Escisión

RESUMEN

Nucleotide excision repair (NER) clears genomes of DNA adducts formed by UV light, environmental agents, and antitumor drugs. Gene mutations that lead to defects in the core NER reaction cause the skin cancer-prone disease xeroderma pigmentosum. In NER, DNA lesions are excised within an oligonucleotide of 25-30 residues via a complex, multi-step reaction that is regulated by protein-protein interactions. These interactions were first characterized in the 1990s using pull-down, co-IP and yeast two-hybrid assays. More recently, high-resolution structures and detailed functional studies have started to yield detailed pictures of the progression along the NER reaction coordinate. In this review, we highlight how the study of interactions among proteins by structural and/or functional studies have provided insights into the mechanisms by which the NER machinery recognizes and excises DNA lesions. Furthermore, we identify reported, but poorly characterized or unsubstantiated interactions in need of further validation.

Asunto(s)

Reparación por Escisión , Humanos , ADN/metabolismo , Daño del ADN , Proteínas de Unión al ADN/metabolismo , Unión Proteica/genética

RESUMEN

Xeroderma pigmentosum is a rare autosomal recessive disorder resulting in heightened cutaneous photosensitivity due to aberrant DNA repair mechanisms. Early-life developmental delay and cognitive impairment have been described in xeroderma pigmentosum cases. However, psychiatric symptoms in adulthood as the presenting feature of xeroderma pigmentosum have not been reported. We report a young adult with xeroderma pigmentosum group G presenting with prominent neuropsychiatric manifestations and evidence of neurodegeneration. The clinical, laboratory, and radiological findings, skin biopsy, and the results of the genetic testing of the patient have been described after obtaining written and informed consent. A young adult male with skin photosensitivity since infancy developed hyper-religiosity, delusions, suicidal ideations, speech hypernasality, lower limb spasticity, and cognitive impairment over the past four years. The MRI of the brain showed diffuse cerebral atrophy. The skin biopsy from bilateral cheeks showed evidence of flattening and thinning of rete ridges, pigment incontinence, and perivascular and periappendageal inflammatory infiltrate. The whole exome sequencing in ethylenediaminetetraacetic acid (EDTA) blood revealed a compound heterozygous likely pathogenic mutation in intron 13 (c.2880-2A>G (3' splice site)) and a mutation in exon 15 (c.3146del (p.Asp1049ValfsTer12)) in the ERCC5 gene suggestive of xeroderma pigmentosum group G. This case highlights that prominent neuropsychiatric features in adulthood can occur due to xeroderma pigmentosum. Thus, xeroderma pigmentosum group G should be considered as a possibility among young adults presenting with neuropsychiatric features, evidence of neurodegeneration, and early-life skin photosensitivity.

RESUMEN

NEIL1 is a DNA glycosylase that recognizes and initiates base excision repair of oxidized bases. The ubiquitous ssDNA binding scaffolding protein, replication protein A (RPA), modulates NEIL1 activity in a manner that depends on DNA structure. Interaction between NEIL1 and RPA has been reported, but the molecular basis of this interaction has yet to be investigated. Using a combination of NMR spectroscopy and isothermal titration calorimetry (ITC), we show that NEIL1 interacts with RPA through two contact points. An interaction with the RPA32C protein recruitment domain was mapped to a motif in the common interaction domain (CID) of NEIL1 and a dissociation constant (Kd) of 200 nM was measured. A substantially weaker secondary interaction with the tandem RPA70AB ssDNA binding domains was also mapped to the CID. Together these two contact points reveal NEIL1 has a high overall affinity (Kd ∼ 20 nM) for RPA. A homology model of the complex of RPA32C with the NEIL1 RPA binding motif in the CID was generated and used to design a set of mutations in NEIL1 to disrupt the interaction, which was confirmed by ITC. The mutant NEIL1 remains catalytically active against a thymine glycol lesion in duplex DNA in vitro. Testing the functional effect of disrupting the NEIL1-RPA interaction in vivo using a Fluorescence Multiplex-Host Cell Reactivation (FM-HCR) reporter assay revealed an unexpected role for NEIL1 in nucleotide excision repair. These findings are discussed in the context of the role of NEIL1 in replication-associated repair.

RESUMEN

Objective: Nucleotide excision repair (NER) plays a vital role in maintaining genome stability, and the effect of NER gene polymorphisms on hepatoblastoma susceptibility is still under investigation. This study aimed to evaluate the relationship between NER gene polymorphisms and the risk of hepatoblastoma in Eastern Chinese Han children. Methods: In this five-center case-control study, we enrolled 966 subjects from East China (193 hepatoblastoma patients and 773 healthy controls). The TaqMan method was used to genotype 19 single nucleotide polymorphisms (SNPs) in NER pathway genes, including ERCC1, XPA, XPC, XPD, XPF, and XPG. Then, multivariate logistic regression analysis was performed, and odds ratios (ORs) and 95% confidence intervals (95% CIs) were utilized to assess the strength of associations. Results: Three SNPs were related to hepatoblastoma risk. XPC rs2229090 and XPD rs3810366 significantly contributed to hepatoblastoma risk according to the dominant model (adjusted OR=1.49, 95% CI=1.07-2.08, P=0.019; adjusted OR=1.66, 95% CI=1.12-2.45, P=0.012, respectively). However, XPD rs238406 conferred a significantly decreased risk of hepatoblastoma under the dominant model (adjusted OR=0.68, 95% CI=0.49-0.95; P=0.024). Stratified analysis demonstrated that these significant associations were more prominent in certain subgroups. Moreover, there was evidence of functional implications of these significant SNPs suggested by online expression quantitative trait loci (eQTLs) and splicing quantitative trait loci (sQTLs) analysis. Conclusions: In summary, NER pathway gene polymorphisms (XPC rs2229090, XPD rs3810366, and XPD rs238406) are significantly associated with hepatoblastoma risk, and further research is required to verify these findings.

RESUMEN

Nucleotide excision repair (NER) is a major DNA repair system and hereditary defects in this system cause critical genetic diseases (e.g., xeroderma pigmentosum, Cockayne syndrome, and trichothiodystrophy). Various proteins are involved in the eukaryotic NER system and undergo several post-translational modifications. Damaged DNA-binding protein 2 (DDB2) is a DNA damage recognition factor in the NER pathway. We previously demonstrated that DDB2 was SUMOylated in response to UV irradiation; however, its physiological roles remain unclear. We herein analyzed several mutants and showed that the N-terminal tail of DDB2 was the target for SUMOylation; however, this region did not contain a consensus SUMOylation sequence. We found a SUMO-interacting motif (SIM) in the N-terminal tail that facilitated SUMOylation. The ubiquitination of a SUMOylation-deficient DDB2 SIM mutant was decreased and its retention of chromatin was prolonged. The SIM mutant showed impaired NER, possibly due to a decline in the timely handover of the lesion site to XPC. These results suggest that the SUMOylation of DDB2 facilitates NER through enhancements in ubiquitination.

RESUMEN

Background: Trichothiodystrophy-1 (TTD1) is an autosomal-recessive disease and caused by mutations in ERCC2, a gene coding for a subunit of the TFIIH transcription and nucleotide-excision repair (NER) factor. In almost half of these patients infectious susceptibility has been reported but the underlying molecular mechanism leading to immunodeficiency is largely unknown. Objective: The aim of this study was to perform extended molecular and immunological phenotyping in patients suffering from TTD1. Methods: Cellular immune phenotype was investigated using multicolor flow cytometry. DNA repair efficiency was evaluated in UV-irradiation assays. Furthermore, early BCR activation events and proliferation of TTD1 lymphocytes following DNA damage induction was tested. In addition, we performed differential gene expression analysis in peripheral lymphocytes of TTD1 patients. Results: We investigated three unrelated TTD1 patients who presented with recurrent infections early in life of whom two harbored novel ERCC2 mutations and the third patient is a carrier of previously described pathogenic ERCC2 mutations. Hypogammaglobulinemia and decreased antibody responses following vaccination were found. TTD1 B-cells showed accumulation of γ-H2AX levels, decreased proliferation activity and reduced cell viability following UV-irradiation. mRNA sequencing analysis revealed significantly downregulated genes needed for B-cell development and activation. Analysis of B-cell subpopulations showed low numbers of naïve and transitional B-cells in TTD1 patients, indicating abnormal B-cell differentiation in vivo. Conclusion: In summary, our analyses confirmed the pathogenicity of novel ERCC2 mutations and show that ERCC2 deficiency is associated with antibody deficiency most likely due to altered B-cell differentiation resulting from impaired BCR-mediated B-cell activation and activation-induced gene transcription.

Asunto(s)

Linfocitos B , Mutación , Proteína de la Xerodermia Pigmentosa del Grupo D , Humanos , Linfocitos B/inmunología , Proteína de la Xerodermia Pigmentosa del Grupo D/genética , Proteína de la Xerodermia Pigmentosa del Grupo D/deficiencia , Masculino , Femenino , Síndromes de Tricotiodistrofia/genética , Síndromes de Tricotiodistrofia/inmunología , Reparación del ADN , Niño , Activación de Linfocitos/genética , Preescolar , Adolescente

RESUMEN

The change of repair efficiency of UV-induced pyrimidine dimers due to aging was examined in replicatively senesced fibroblasts. The fibroblasts with repeated passages showed the characteristics of cellular senescence, including irreversible cell cycle arrest, elevated ß-galactosidase activity, and senescence-associated secretory phenotype. The incision efficiency of oligonucleotide containing UV lesions was similar regardless of cell doubling levels, but the gap filling process was impaired in replicatively senescent cells. The releases of xeroderma pigmentosum group G, proliferating cell nuclear antigen, and replication protein A from damaged sites were delayed, which might have disturbed the DNA polymerase progression. The persistent single-stranded DNA was likely converted to double-strand breaks, leading to ataxia telangiectasia-mutated phosphorylation and 53BP1 foci formation. Phosphorylated histone H2AX (γ-H2AX) induction mainly occurred in G1 phase in senescent cells, not in S phase such as in normal cells, indicating that replication stress-independent double-strand breaks might be formed. MRE11 having nuclease activity accumulated to damaged sites at early time point after UV irradiation but not released in senescent cells. The pharmacological studies using specific inhibitors for the nuclease activity suggested that MRE11 contributed to the enlargement of single-stranded DNA gap, facilitating the double-strand break formation.

RESUMEN

In budding yeast, Rad5 and Rad7-Rad16 play respective roles in the error-free post-replication repair and nucleotide excision repair of ultraviolet-induced DNA damage; however, their homologs have not yet been studied in non-yeast fungi. In the fungus Beauveria bassiana, a deficiency in the Rad7 homolog, Rad5 ortholog and two Rad16 paralogs (Rad16A/B) instituted an ability to help the insect-pathogenic fungus to recover from solar UVB damage through photoreactivation. The fungal lifecycle-related phenotypes were not altered in the absence of rad5, rad16A or rad16B, while severe defects in growth and conidiation were caused by the double deletion of rad16A and rad16B. Compared with the wild-type and complemented strains, the mutants showed differentially reduced activities regarding the resilience of UVB-impaired conidia at 25 °C through a 12-h incubation in a regime of visible light plus dark (L/D 3:9 h or 5:7 h for photoreactivation) or of full darkness (dark reactivation) mimicking a natural nighttime. The estimates of the median lethal UVB dose LD50 from the dark and L/D treatments revealed greater activities of Rad5 and Rad16B than of Rad16A and additive activities of Rad16A and Rad16B in either NER-dependent dark reactivation or photorepair-dependent photoreactivation. However, their dark reactivation activities were limited to recovering low UVB dose-impaired conidia but were unable to recover conidia impaired by sublethal and lethal UVB doses as did their photoreactivation activities at L/D 3:9 or 5:7, unless the night/dark time was doubled or further prolonged. Therefore, the anti-UV effects of Rad5, Rad16A and Rad16B in B. bassiana depend primarily on photoreactivation and are mechanistically distinct from those for their yeast homologs.

RESUMEN

Transcription is extremely important for cellular processes but can be hindered by RNA polymerase II (RNAPII) pausing and stalling. Cockayne syndrome protein B (CSB) promotes the progression of paused RNAPII or initiates transcription-coupled nucleotide excision repair (TC-NER) to remove stalled RNAPII. However, the specific mechanism by which CSB initiates TC-NER upon damage remains unclear. In this study, we identified the indispensable role of the ARK2N-CK2 complex in the CSB-mediated initiation of TC-NER. The ARK2N-CK2 complex is recruited to damage sites through CSB and then phosphorylates CSB. Phosphorylation of CSB enhances its binding to stalled RNAPII, prolonging the association of CSB with chromatin and promoting CSA-mediated ubiquitination of stalled RNAPII. Consistent with this finding, Ark2n-/- mice exhibit a phenotype resembling Cockayne syndrome. These findings shed light on the pivotal role of the ARK2N-CK2 complex in governing the fate of RNAPII through CSB, bridging a critical gap necessary for initiating TC-NER.

Asunto(s)

Síndrome de Cockayne , ADN Helicasas , Enzimas Reparadoras del ADN , Reparación del ADN , Proteínas de Unión a Poli-ADP-Ribosa , ARN Polimerasa II , Enzimas Reparadoras del ADN/metabolismo , Enzimas Reparadoras del ADN/genética , ARN Polimerasa II/metabolismo , ARN Polimerasa II/genética , Proteínas de Unión a Poli-ADP-Ribosa/metabolismo , Proteínas de Unión a Poli-ADP-Ribosa/genética , Humanos , Animales , Ratones , ADN Helicasas/metabolismo , ADN Helicasas/genética , Síndrome de Cockayne/genética , Síndrome de Cockayne/metabolismo , Transcripción Genética , Fosforilación , Quinasa de la Caseína II/metabolismo , Quinasa de la Caseína II/genética , Ratones Noqueados , Daño del ADN , ATPasas Asociadas con Actividades Celulares Diversas/metabolismo , ATPasas Asociadas con Actividades Celulares Diversas/genética , Cromatina/metabolismo , Ubiquitinación , Reparación por Escisión

RESUMEN

UV light is a potent mutagen that induces bulky DNA damage in the form of cyclobutane pyrimidine dimers (CPDs). Photodamage and other bulky lesions occurring in nuclear genomes can be repaired through nucleotide excision repair (NER), where incisions on both sides of a damaged site precede the removal of a single-stranded oligonucleotide containing the damage. Mitochondrial genomes (mtDNAs) are also susceptible to damage from UV light, but current evidence suggests that the only way to eliminate bulky mtDNA damage is through mtDNA degradation. Damage-containing oligonucleotides excised during NER can be captured with antidamage antibodies and sequenced (XR-seq) to produce high-resolution maps of active repair locations following UV exposure. We analyzed previously published datasets from Arabidopsis thaliana, Saccharomyces cerevisiae, and Drosophila melanogaster to identify reads originating from the mtDNA (and plastid genome in A. thaliana). In A. thaliana and S. cerevisiae, the mtDNA-mapping reads have unique length distributions compared to the nuclear-mapping reads. The dominant fragment size was 26 nt in S. cerevisiae and 28 nt in A. thaliana with distinct secondary peaks occurring in regular intervals. These reads also show a nonrandom distribution of di-pyrimidines (the substrate for CPD formation) with TT enrichment at positions 7-8 of the reads. Therefore, UV damage to mtDNA appears to result in production of DNA fragments of characteristic lengths and positions relative to the damaged location. The mechanisms producing these fragments are unclear, but we hypothesize that they result from a previously uncharacterized DNA degradation pathway or repair mechanism in mitochondria.

Asunto(s)

Arabidopsis , Daño del ADN , Reparación del ADN , ADN Mitocondrial , Drosophila melanogaster , Saccharomyces cerevisiae , Rayos Ultravioleta , ADN Mitocondrial/genética , Arabidopsis/genética , Arabidopsis/efectos de la radiación , Rayos Ultravioleta/efectos adversos , Animales , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/efectos de la radiación , Saccharomyces cerevisiae/metabolismo , Drosophila melanogaster/genética , Dímeros de Pirimidina/genética , Dímeros de Pirimidina/metabolismo , Genoma Mitocondrial

RESUMEN

DNA repair pathways play a critical role in genome stability, but in eukaryotic cells, they must operate to repair DNA lesions in the compact and tangled environment of chromatin. Previous studies have shown that the packaging of DNA into nucleosomes, which form the basic building block of chromatin, has a profound impact on DNA repair. In this review, we discuss the principles and mechanisms governing DNA repair in chromatin. We focus on the role of histone post-translational modifications (PTMs) in repair, as well as the molecular mechanisms by which histone mutants affect cellular sensitivity to DNA damage agents and repair activity in chromatin. Importantly, these mechanisms are thought to significantly impact somatic mutation rates in human cancers and potentially contribute to carcinogenesis and other human diseases. For example, a number of the histone mutants studied primarily in yeast have been identified as candidate oncohistone mutations in different cancers. This review highlights these connections and discusses the potential importance of DNA repair in chromatin to human health.

Asunto(s)

Reparación del ADN , Histonas , Mutación , Nucleosomas , Procesamiento Proteico-Postraduccional , Nucleosomas/metabolismo , Nucleosomas/genética , Humanos , Histonas/metabolismo , Histonas/genética , Animales , Daño del ADN , Neoplasias/genética , Neoplasias/metabolismo , Código de Histonas , Cromatina/metabolismo , Cromatina/genética

RESUMEN

The ultraviolet (UV) component of sunlight can damage DNA. Although most solar UV is absorbed by the ozone layer, wavelengths > 300 nm (UVA and UVB bands) can reach the Earth's surface. It is essential to understand the genotoxic effects of UV light, particularly in natural environments. Caulobacter crescentus, a bacterium widely employed as a model for cell cycle studies, was selected for this study. Strains proficient and deficient in DNA repair (uvrA-) were used to concurrently investigate three genotoxic endpoints: cytotoxicity, SOS induction, and gene mutation, using colony-formation, the SOS chromotest, and RifR mutagenesis, respectively. Our findings underscore the distinct impacts of individual UV bands and the full spectrum of sunlight itself in C. crescentus. UVC light was highly genotoxic, especially for the repair-deficient strain. A UVB dose equivalent to 20 min sunlight exposure also affected the cells. UVA exposure caused a significant response only at high doses, likely due to activation of photorepair. Exposure to solar irradiation resulted in reduced levels of SOS induction, possibly due to decreased cell survival. However, mutagenicity is increased, particularly in uvrA- deficient cells.

Asunto(s)

Caulobacter crescentus , Rayos Ultravioleta , Rayos Ultravioleta/efectos adversos , Caulobacter crescentus/genética , Daño del ADN , Reparación del ADN , Mutación

RESUMEN

The pathogenesis of inflammatory bowel disease (IBD) remains unclear and is associated with an increased risk of developing colitis-associated cancer (CAC). Under sustained inflammatory stimulation in the intestines, loss of early DNA damage response genes can lead to tumor formation. Many proteins are involved in the pathways of DNA damage response and play critical roles in protecting genes from various potential damages that DNA may undergo. ERCC4 is a structure-specific endonuclease that participates in the nucleotide excision repair (NER) pathway. The catalytic site of ERCC4 determines the activity of NER and is an indispensable gene in the NER pathway. ERCC4 may be involved in the imbalanced process of DNA damage and repair in IBD-related inflammation and CAC. This article primarily reviews the function of ERCC4 in the DNA repair pathway and discusses its potential role in the processes of IBD-related inflammation and carcinogenesis. Finally, we explore how this knowledge may open novel avenues for the treatment of IBD and IBD-related cancer.

Asunto(s)

Neoplasias Colorrectales , Enfermedades Inflamatorias del Intestino , Humanos , Reparación del ADN , Enfermedades Inflamatorias del Intestino/complicaciones , Enfermedades Inflamatorias del Intestino/genética , Inflamación/complicaciones , Daño del ADN , Neoplasias Colorrectales/genética , Neoplasias Colorrectales/patología

RESUMEN

During transcription-coupled DNA repair (TCR) the detection of DNA damage and initiation of nucleotide excision repair (NER) is performed by translocating RNA polymerases (RNAP), which are arrested upon encountering bulky DNA lesions. Two opposing models of the subsequent steps of TCR in bacteria exist. In the first model, stalled RNAPs are removed from the damage site by recruitment of Mfd which dislodges RNAP by pushing it forwards before recruitment of UvrA and UvrB. In the second model, UvrD helicase backtracks RNAP from the lesion site. Recent studies have proposed that both UvrD and UvrA continuously associate with RNAP before damage occurs, which forms the primary damage sensor for NER. To test these two models of TCR in living E. coli, we applied super-resolution microscopy (PALM) combined with single particle tracking to directly measure the mobility and recruitment of Mfd, UvrD, UvrA, and UvrB to DNA during ultraviolet-induced DNA damage. The intracellular mobilities of NER proteins in the absence of DNA damage showed that most UvrA molecules could in principle be complexed with RNAP, however, this was not the case for UvrD. Upon DNA damage, Mfd recruitment to DNA was independent of the presence of UvrA, in agreement with its role upstream of this protein in the TCR pathway. In contrast, UvrD recruitment to DNA was strongly dependent on the presence of UvrA. Inhibiting transcription with rifampicin abolished Mfd DNA-recruitment following DNA damage, whereas significant UvrD, UvrA, and UvrB recruitment remained, consistent with a UvrD and UvrA performing their NER functions independently of transcribing RNAP. Together, although we find that up to ∼8 UvrD-RNAP-UvrA complexes per cell could potentially form in the absence of DNA damage, our live-cell data is not consistent with this complex being the primary DNA damage sensor for NER.

Asunto(s)

Proteínas de Escherichia coli , Escherichia coli , Escherichia coli/genética , Escherichia coli/metabolismo , Factores de Transcripción/metabolismo , Imagen Individual de Molécula , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Proteínas Bacterianas/metabolismo , Reparación del ADN , Daño del ADN , ARN Polimerasas Dirigidas por ADN/metabolismo , ADN/metabolismo , Receptores de Antígenos de Linfocitos T/genética , Receptores de Antígenos de Linfocitos T/metabolismo , ADN Helicasas/metabolismo

RESUMEN

Increasing antimicrobial drug resistance represents a global existential threat. Infection is a particular problem in immunocompromised individuals, such as patients undergoing cancer chemotherapy, due to the targeting of rapidly dividing cells by antineoplastic agents. We recently developed a strategy that targets bacterial nucleotide excision DNA repair (NER) to identify compounds that act as antimicrobial sensitizers specific for patients undergoing cancer chemotherapy. Building on this, we performed a virtual drug screening of a ~120,000 compound library against the key NER protein UvrA. From this, numerous target compounds were identified and of those a candidate compound, Bemcentinib (R428), showed a strong affinity toward UvrA. This NER protein possesses four ATPase sites in its dimeric state, and we found that Bemcentinib could inhibit UvrA's ATPase activity by ~90% and also impair its ability to bind DNA. As a result, Bemcentinib strongly diminishes NER's ability to repair DNA in vitro. To provide a measure of in vivo activity we discovered that the growth of Escherichia coli MG1655 was significantly inhibited when Bemcentinib was combined with the DNA damaging agent 4-NQO, which is analogous to UV. Using the clinically relevant DNA-damaging antineoplastic cisplatin in combination with Bemcentinib against the urological sepsis-causing E. coli strain EC958 caused complete growth inhibition. This study offers a novel approach for the potential development of new compounds for use as adjuvants in antineoplastic therapy.

Asunto(s)

Antineoplásicos , Benzocicloheptenos , Proteínas de Escherichia coli , Neoplasias , Triazoles , Humanos , Escherichia coli/genética , Escherichia coli/metabolismo , Reparación del ADN , Daño del ADN , Antineoplásicos/farmacología , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , ADN/metabolismo , Adenosina Trifosfatasas/metabolismo