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1.
Anticancer Res ; 40(10): 5631-5639, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32988887

RESUMO

BACKGROUND/AIM: DNA damage response (DDR), wherein p21 is a cell fate determinant, is a potential cancer therapeutic target. Molecular expression during DDR was explored in ovarian clear-cell carcinoma (CCC). MATERIALS AND METHODS: CHK1, CHK2, TP53 and p21 expression in DDR was examined using immunostaining in surgical sections of CCC (n=22). Molecular alterations in two types of CCC cell lines, JHOC-5 and JHOC-9, were investigated using western blot analysis. RESULTS: Expression of DDR-associated molecules was noted in most patients. While high p21 expression was found in half of the patients, the remaining patients exhibited low p21 expression. Treatment with UC2288, a p21 inhibitor, attenuated proliferation of both cell lines, more prominently in JHOC-9, resulting in reduced viability and subsequent apoptosis. CONCLUSION: p21 Inhibitor induced cell death in cells with high p21 expression, suggesting that p21 suppression can be a therapeutic strategy to treat patients with CCC.


Assuntos
Quinase 1 do Ponto de Checagem/genética , Quinase do Ponto de Checagem 2/genética , Inibidor de Quinase Dependente de Ciclina p21/genética , Neoplasias Ovarianas/genética , Proteína Supressora de Tumor p53/genética , Adulto , Idoso , Apoptose/genética , Linhagem Celular Tumoral , Proliferação de Células/genética , Dano ao DNA/genética , Feminino , Regulação Neoplásica da Expressão Gênica , Humanos , Pessoa de Meia-Idade , Neoplasias Ovarianas/patologia
2.
Nat Commun ; 11(1): 4124, 2020 08 17.
Artigo em Inglês | MEDLINE | ID: mdl-32807787

RESUMO

In response to DNA damage, a synthetic lethal relationship exists between the cell cycle checkpoint kinase MK2 and the tumor suppressor p53. Here, we describe the concept of augmented synthetic lethality (ASL): depletion of a third gene product enhances a pre-existing synthetic lethal combination. We show that loss of the DNA repair protein XPA markedly augments the synthetic lethality between MK2 and p53, enhancing anti-tumor responses alone and in combination with cisplatin chemotherapy. Delivery of siRNA-peptide nanoplexes co-targeting MK2 and XPA to pre-existing p53-deficient tumors in a highly aggressive, immunocompetent mouse model of lung adenocarcinoma improves long-term survival and cisplatin response beyond those of the synthetic lethal p53 mutant/MK2 combination alone. These findings establish a mechanism for co-targeting DNA damage-induced cell cycle checkpoints in combination with repair of cisplatin-DNA lesions in vivo using RNAi nanocarriers, and motivate further exploration of ASL as a generalized strategy to improve cancer treatment.


Assuntos
Pontos de Checagem do Ciclo Celular/fisiologia , Reparo do DNA/fisiologia , Animais , Pontos de Checagem do Ciclo Celular/genética , Linhagem Celular Tumoral , Dano ao DNA/genética , Dano ao DNA/fisiologia , Reparo do DNA/genética , Células HCT116 , Humanos , Immunoblotting , Camundongos , Microscopia Eletrônica de Transmissão , Microscopia de Fluorescência , Nanomedicina/métodos , Interferência de RNA , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo
3.
Mol Cell ; 79(6): 934-949.e14, 2020 09 17.
Artigo em Inglês | MEDLINE | ID: mdl-32822587

RESUMO

Although ADP-ribosylation of histones by PARP-1 has been linked to genotoxic stress responses, its role in physiological processes and gene expression has remained elusive. We found that NAD+-dependent ADP-ribosylation of histone H2B-Glu35 by small nucleolar RNA (snoRNA)-activated PARP-1 inhibits AMP kinase-mediated phosphorylation of adjacent H2B-Ser36, which is required for the proadipogenic gene expression program. The activity of PARP-1 on H2B requires NMNAT-1, a nuclear NAD+ synthase, which directs PARP-1 catalytic activity to Glu and Asp residues. ADP-ribosylation of Glu35 and the subsequent reduction of H2B-Ser36 phosphorylation inhibits the differentiation of adipocyte precursors in cultured cells. Parp1 knockout in preadipocytes in a mouse lineage-tracing genetic model increases adipogenesis, leading to obesity. Collectively, our results demonstrate a functional interplay between H2B-Glu35 ADP-ribosylation and H2B-Ser36 phosphorylation that controls adipogenesis.


Assuntos
ADP-Ribosilação/genética , Adipogenia/genética , Histonas/genética , Poli(ADP-Ribose) Polimerase-1/genética , Adenosina Difosfato Ribose/genética , Adipócitos/metabolismo , Adipócitos/patologia , Animais , Linhagem Celular , Dano ao DNA/genética , Regulação da Expressão Gênica no Desenvolvimento/genética , Camundongos , Fosforilação/genética , RNA Nucleolar Pequeno/genética
4.
PLoS One ; 15(8): e0236881, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32745107

RESUMO

PIERCE1, p53 induced expression 1 in Rb null cells, is a novel p53 target involved in the DNA damage response and cell cycle in mice. These facts prompted us to study the function of PIERCE1 with respect to p53-associated pathophysiology of cancer in humans. Unexpectedly, PIERCE1 did not respond to overexpression and activation of p53 in humans. In this study, we swapped p53 protein expression in human and mouse cells to find the clue of this difference between species. Human p53 expression in mouse cells upregulated PIERCE1 expression, suggesting that p53-responsive elements on the PIERCE1 promoter are crucial, but not the p53 protein itself. Indeed, in silico analyses of PIERCE1 promoters revealed that p53-responsive elements identified in mice are not conserved in humans. Consistently, chromatin immunoprecipitation-sequencing (ChIP-seq) analyses confirmed p53 enrichment against the PIERCE1 promoter region in mice, not in human cells. To complement the p53 study in mice, further promoter analyses suggested that the human PIERCE1 promoter is more similar to guinea pigs, lemurs, and dogs than to rodents. Taken together, our results confirm the differential responsiveness of PIERCE1 expression to p53 due to species differences in PIERCE1 promoters. The results also show partial dissimilarity after p53 induction between mice and humans.


Assuntos
Proteínas de Ciclo Celular , Elementos de Resposta/genética , Proteína Supressora de Tumor p53/metabolismo , Animais , Ciclo Celular/genética , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Linhagem Celular Tumoral , Dano ao DNA/genética , Humanos , Camundongos , Regiões Promotoras Genéticas , Transcrição Genética/fisiologia
5.
PLoS Genet ; 16(7): e1008828, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32609721

RESUMO

Homologous recombination (HR) has an intimate relationship with genome replication, both during repair of DNA lesions that might prevent DNA synthesis and in tackling stalls to the replication fork. Recent studies led us to ask if HR might have a more central role in replicating the genome of Leishmania, a eukaryotic parasite. Conflicting evidence has emerged regarding whether or not HR genes are essential, and genome-wide mapping has provided evidence for an unorthodox organisation of DNA replication initiation sites, termed origins. To answer this question, we have employed a combined CRISPR/Cas9 and DiCre approach to rapidly generate and assess the effect of conditional ablation of RAD51 and three RAD51-related proteins in Leishmania major. Using this approach, we demonstrate that loss of any of these HR factors is not immediately lethal but in each case growth slows with time and leads to DNA damage and accumulation of cells with aberrant DNA content. Despite these similarities, we show that only loss of RAD51 or RAD51-3 impairs DNA synthesis and causes elevated levels of genome-wide mutation. Furthermore, we show that these two HR factors act in distinct ways, since ablation of RAD51, but not RAD51-3, has a profound effect on DNA replication, causing loss of initiation at the major origins and increased DNA synthesis at subtelomeres. Our work clarifies questions regarding the importance of HR to survival of Leishmania and reveals an unanticipated, central role for RAD51 in the programme of genome replication in a microbial eukaryote.


Assuntos
Recombinação Homóloga/genética , Leishmania major/genética , Leishmaniose Cutânea/genética , Rad51 Recombinase/genética , Sistemas CRISPR-Cas/genética , Dano ao DNA/genética , Reparo do DNA/genética , Replicação do DNA/genética , Técnicas de Inativação de Genes , Genoma/genética , Humanos , Leishmania major/patogenicidade , Leishmaniose Cutânea/parasitologia
6.
Nat Commun ; 11(1): 3503, 2020 07 14.
Artigo em Inglês | MEDLINE | ID: mdl-32665547

RESUMO

DNA replication timing is tightly regulated during S-phase. S-phase length is determined by DNA synthesis rate, which depends on the number of active replication forks and their velocity. Here, we show that E2F-dependent transcription, through E2F6, determines the replication capacity of a cell, defined as the maximal amount of DNA a cell can synthesise per unit time during S-phase. Increasing or decreasing E2F-dependent transcription during S-phase increases or decreases replication capacity, and thereby replication rates, thus shortening or lengthening S-phase, respectively. The changes in replication rate occur mainly through changes in fork speed without affecting the number of active forks. An increase in fork speed does not induce replication stress directly, but increases DNA damage over time causing cell cycle arrest. Thus, E2F-dependent transcription determines the DNA replication capacity of a cell, which affects the replication rate, controlling the time it takes to duplicate the genome and complete S-phase.


Assuntos
Cromatina/metabolismo , Replicação do DNA/fisiologia , Western Blotting , Cromatina/genética , Dano ao DNA/genética , Dano ao DNA/fisiologia , Replicação do DNA/genética , Fatores de Transcrição E2F/genética , Fatores de Transcrição E2F/metabolismo , Citometria de Fluxo , Imunofluorescência , Humanos , Fase S/genética , Fase S/fisiologia , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
7.
Mutat Res ; 854-855: 503199, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32660827

RESUMO

The bacterial reverse mutation test (Ames test) is the most commonly used genotoxicity test; it is a primary component of the chemical safety assessment data required by regulatory agencies worldwide. Within the current accepted in vitro genotoxicity test battery, it is considered capable of revealing DNA reactivity, and identifying substances that can produce gene mutations via different mechanisms. The previously published consolidated EURL ECVAM Genotoxicity and Carcinogenicity Database, which includes substances that elicited a positive response in the Ames test, constitutes a collection of data that serves as a reference for a number of regulatory activities in the area of genotoxicity testing. Consequently, we considered it important to expand the database to include substances that fail to elicit a positive response in the Ames test, i.e., Ames negative substances. Here, we describe a curated collection of 211 Ames negative substances, with a summary of complementary data available for other genotoxicity endpoints in vitro and in vivo, plus available carcinogenicity data. A descriptive analysis of the data is presented. This includes a representation of the chemical space formed by the Ames-negative database with respect to other substances (e.g. REACH registered substances, approved drugs, pesticides, etc.) and a description of the organic functional groups found in the database. We also provide some suggestions on further analyses that could be made.


Assuntos
Testes de Carcinogenicidade/normas , Carcinógenos/toxicidade , Bases de Dados Factuais/normas , Testes de Mutagenicidade/normas , Mutagênicos/toxicidade , Resultados Negativos/normas , Animais , Dano ao DNA/efeitos dos fármacos , Dano ao DNA/genética , Gerenciamento de Dados/normas , Humanos
8.
J Vis Exp ; (160)2020 06 26.
Artigo em Inglês | MEDLINE | ID: mdl-32658192

RESUMO

Mammalian cells are constantly exposed to chemicals, radiations, and naturally occurring metabolic by-products, which create specific types of DNA insults. Genotoxic agents can damage the DNA backbone, break it, or modify the chemical nature of individual bases. Following DNA insult, DNA damage response (DDR) pathways are activated and proteins involved in the repair are recruited. A plethora of factors are involved in sensing the type of damage and activating the appropriate repair response. Failure to correctly activate and recruit DDR factors can lead to genomic instability, which underlies many human pathologies including cancer. Studies of DDR proteins can provide insights into genotoxic drug response and cellular mechanisms of drug resistance. There are two major ways of visualizing proteins in vivo: direct observation, by tagging the protein of interest with a fluorescent protein and following it by live imaging, or indirect immunofluorescence on fixed samples. While visualization of fluorescently tagged proteins allows precise monitoring over time, direct tagging in N- or C-terminus can interfere with the protein localization or function. Observation of proteins in their unmodified, endogenous version is preferred. When DNA repair proteins are recruited to the DNA insult, their concentration increases locally and they form groups, or "foci", that can be visualized by indirect immunofluorescence using specific antibodies. Although detection of protein foci does not provide a definitive proof of direct interaction, co-localization of proteins in cells indicates that they regroup to the site of damage and can inform of the sequence of events required for complex formation. Careful analysis of foci spatial overlap in cells expressing wild type or mutant versions of a protein can provide precious clues on functional domains important for DNA repair function. Last, co-localization of proteins indicates possible direct interactions that can be verified by co-immunoprecipitation in cells, or direct pulldown using purified proteins.


Assuntos
Dano ao DNA/genética , Reparo do DNA/genética , Imunofluorescência/métodos , Animais , Humanos
9.
Nucleic Acids Res ; 48(15): 8461-8473, 2020 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-32633759

RESUMO

DNA polymerase ζ (Pol ζ) and Rev1 are essential for the repair of DNA interstrand crosslink (ICL) damage. We have used yeast DNA polymerases η, ζ and Rev1 to study translesion synthesis (TLS) past a nitrogen mustard-based interstrand crosslink (ICL) with an 8-atom linker between the crosslinked bases. The Rev1-Pol ζ complex was most efficient in complete bypass synthesis, by 2-3 fold, compared to Pol ζ alone or Pol η. Rev1 protein, but not its catalytic activity, was required for efficient TLS. A dCMP residue was faithfully inserted across the ICL-G by Pol η, Pol ζ, and Rev1-Pol ζ. Rev1-Pol ζ, and particularly Pol ζ alone showed a tendency to stall before the ICL, whereas Pol η stalled just after insertion across the ICL. The stalling of Pol η directly past the ICL is attributed to its autoinhibitory activity, caused by elongation of the short ICL-unhooked oligonucleotide (a six-mer in our study) by Pol η providing a barrier to further elongation of the correct primer. No stalling by Rev1-Pol ζ directly past the ICL was observed, suggesting that the proposed function of Pol ζ as an extender DNA polymerase is also required for ICL repair.


Assuntos
DNA Polimerase Dirigida por DNA/genética , DNA/genética , Nucleotidiltransferases/genética , Proteínas de Saccharomyces cerevisiae/genética , Estruturas Cromossômicas/efeitos dos fármacos , Estruturas Cromossômicas/genética , Dano ao DNA/efeitos dos fármacos , Dano ao DNA/genética , Reparo do DNA/efeitos dos fármacos , Reparo do DNA/genética , Replicação do DNA/genética , Complexos Multiproteicos/genética , Compostos de Mostarda Nitrogenada/farmacologia , Saccharomyces cerevisiae/genética
10.
Nucleic Acids Res ; 48(15): 8474-8489, 2020 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-32652040

RESUMO

Highly toxic DNA double-strand breaks (DSBs) readily trigger the DNA damage response (DDR) in cells, which delays cell cycle progression to ensure proper DSB repair. In Saccharomyces cerevisiae, mitotic S phase (20-30 min) is lengthened upon DNA damage. During meiosis, Spo11-induced DSB onset and repair lasts up to 5 h. We report that the NH2-terminal domain (NTD; residues 1-66) of Rad51 has dual functions for repairing DSBs during vegetative growth and meiosis. Firstly, Rad51-NTD exhibits autonomous expression-enhancing activity for high-level production of native Rad51 and when fused to exogenous ß-galactosidase in vivo. Secondly, Rad51-NTD is an S/T-Q cluster domain (SCD) harboring three putative Mec1/Tel1 target sites. Mec1/Tel1-dependent phosphorylation antagonizes the proteasomal degradation pathway, increasing the half-life of Rad51 from ∼30 min to ≥180 min. Our results evidence a direct link between homologous recombination and DDR modulated by Rad51 homeostasis.


Assuntos
Quebras de DNA de Cadeia Dupla , Endodesoxirribonucleases/genética , Meiose/genética , Rad51 Recombinase/genética , Proteínas de Saccharomyces cerevisiae/genética , Dano ao DNA/genética , Reparo do DNA/genética , Proteínas de Ligação a DNA/genética , Regulação Fúngica da Expressão Gênica/genética , Peptídeos e Proteínas de Sinalização Intracelular/genética , Fosforilação/genética , Complexo de Endopeptidases do Proteassoma/genética , Domínios Proteicos/genética , Proteínas Serina-Treonina Quinases/genética , Proteólise , Saccharomyces cerevisiae/genética , beta-Galactosidase/genética
12.
Mutat Res ; 854-855: 503196, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32660820

RESUMO

DNA is exposed to the attack of several exogenous agents that modify its chemical structure, so cells must repair those changes in order to survive. Alkylating agents introduce methyl or ethyl groups in most of the cyclic or exocyclic nitrogen atoms of the ring and exocyclic oxygen available in DNA bases producing damage that can induce the SOS response in Escherichia coli and many other bacteria. Likewise, ultraviolet light produces mainly cyclobutane pyrimidine dimers that arrest the progression of the replication fork and triggers such response. The need of some enzymes (such as RecO, ExoI and RecJ) in processing injuries produced by gamma radiation prior the induction of the SOS response has been reported before. In the present work, several repair-defective strains of E. coli were treated with methyl methanesulfonate, ethyl methanesulfonate, mitomycin C or ultraviolet light. Both survival and SOS induction (by means of the Chromotest) were tested. Our results indicate that the participation of these genes depends on the type of injury caused by a genotoxin on DNA.


Assuntos
Reparo do DNA/efeitos dos fármacos , Reparo do DNA/genética , Escherichia coli/efeitos dos fármacos , Escherichia coli/genética , Mutagênicos/farmacologia , Resposta SOS em Genética/efeitos dos fármacos , Resposta SOS em Genética/genética , Alquilantes/farmacologia , Proteínas de Bactérias/genética , Dano ao DNA/efeitos dos fármacos , Dano ao DNA/genética , Metanossulfonato de Etila/farmacologia , Metanossulfonato de Metila/farmacologia , Mitomicina/farmacologia , Dímeros de Pirimidina/farmacologia , Raios Ultravioleta/efeitos adversos
13.
Mutat Res ; 854-855: 503197, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32660821

RESUMO

Telomeres, specialized structures at the ends of linear chromosomes, protect chromosome ends from degradation, recombination, and mis-repair. Critically short telomere length (TL) may result in chromosome instability (CIN), causing tumor promotion and, at higher levels, cell death and tumor suppression. Homocysteine (Hcy) is a sulfur-containing amino acid involved in one-carbon metabolism. Elevated plasma Hcy is a cancer risk factor. Human SH-SY5Y neuroblastoma cells were treated with pathophysiological concentrations of Hcy (15-120 µM) for 14 and 28 days. The cytokinesis-block micronucleus cytome assay was used to determine cytostasis (nuclear division index, NDI), cell death (apoptosis and necrosis), and CIN (micronuclei, nucleoplasmic bridges, and nuclear buds in binucleated cells). Quantitative PCR was used to measure TL and the expression of hTERT, the gene encoding the catalytic subunit of telomerase for TL elongation. The results showed that Hcy induced elongation of TL and fluctuating changes in expression of hTERT. TL elongation was associated with increased CIN. Hcy decreased the NDI and increased cell death. This study shows that there is cross-talk between Hcy and TL in tumor cells and supports the concept that high Hcy inhibits cell division and promotes the death of tumor cells by abnormal elongation of TL and elevation of CIN.


Assuntos
Instabilidade Cromossômica/genética , Homocisteína/genética , Neuroblastoma/genética , Telômero/genética , Apoptose/genética , Morte Celular/genética , Divisão Celular/genética , Linhagem Celular Tumoral , Citocinese/genética , Dano ao DNA/genética , Humanos , Micronúcleos com Defeito Cromossômico , Testes para Micronúcleos/métodos , Necrose/genética , Telomerase/genética
14.
Mutat Res ; 854-855: 503200, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32660824

RESUMO

Germ cell tumour (GCT) patients who fail to respond to chemotherapy or who relapse have a poor prognosis. Timely and accurately stratifying such patients could optimise their therapy. We identified endogenous DNA damage levels as a prognostic marker for progression-free (PFS) and overall (OS) survival in chemotherapy-naïve GCT patients. In the present study, we have extended our previous results and reviewed the prognostic power of DNA damage level in GCTs. Endogenous DNA damage levels were measured with the comet assay. Receiver operator characteristic analysis was applied to determine the optimal cut-off value and to evaluate its prognostic accuracy. PFS and OS were estimated by the Kaplan-Meier method and compared using the log-rank test. Hazard ratio (HR) estimates were calculated by Cox regression analysis. A cut-off value of 6.34 provided the highest sensitivity and specificity, with area under curve values of 0.813 and 0.814 for disease progression and mortality, respectively. A % DNA in tail > 6.34 was significantly associated with shorter PFS (HR = 9.54, 95 % confidence interval [CI]: 3.43-26.55, p < 0.001) and OS (HR = 14.62, 95 % CI: 3.14-67.95, p = 0.001) by univariate analysis. The prognostic value of DNA damage measurement was confirmed by multivariate models (HR = 6.45, 95 % CI: 2.22-18.75, p = 0.001 for PFS and HR = 9.40, 95 % CI: 1.70-52.09, p = 0.010 for OS), when HR was adjusted for relevant clinical categories. The added prognostic value of DNA damage in combination with International Germ Cell Cancer Collaborative Group (IGCCCG) risk groups has been revealed. Endogenous DNA damage is an independent prognosticator for PFS and OS in GCT patients and its clinical use, particularly in combination with IGCCCG risk groups, may help in stratifying these patients.


Assuntos
Células Sanguíneas/patologia , Dano ao DNA/genética , Neoplasias Embrionárias de Células Germinativas/genética , Neoplasias Embrionárias de Células Germinativas/patologia , Adulto , Células Cultivadas , Ensaio Cometa/métodos , Progressão da Doença , Intervalo Livre de Doença , Feminino , Humanos , Estimativa de Kaplan-Meier , Leucócitos Mononucleares/patologia , Masculino , Pessoa de Meia-Idade , Prognóstico , Intervalo Livre de Progressão , Modelos de Riscos Proporcionais , Fatores de Risco
15.
Mutat Res ; 854-855: 503202, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32660826

RESUMO

Cancer is a genomic disease associated with accumulation of genetic damage. Cancer-initiating events, such as chromosome breakage, loss and rearrangement, can be used as biomarkers to evaluate individual cancer risk. Cytokinesis-block micronucleus cytome (CBMN - Cyt) assay parameters in peripheral blood lymphocytes (PBL) of thirty four patients diagnosed with high-grade squamous intraepithelial lesions (HSIL) and fifteen healthy women were measured. The genomic instability of patients diagnosed with HSIL were investigated in order to compare differences between the two subgroups of HSIL (CIN 2 and CIN 3). The micronucleus (MN) frequencies in PBL, as well as the frequencies of nucleoplasmic bridges (NPB) and nuclear buds (NBUD) were higher in patients than in controls (Mann- Whitney test, p < 0.05). These results provide evidence that CBMN cytome assay in peripheral blood lymphocytes may be used to identify individuals who are at high risk of developing cervical cancer. Since the extent of DNA damage varies between CIN 2 and CIN 3, these findings support the CIN grading system.


Assuntos
Instabilidade Genômica/genética , Linfócitos/patologia , Lesões Intraepiteliais Escamosas/genética , Lesões Intraepiteliais Escamosas/patologia , Adulto , Idoso , Núcleo Celular/genética , Dano ao DNA/genética , Feminino , Humanos , Testes para Micronúcleos/métodos , Pessoa de Meia-Idade , Neoplasias do Colo do Útero/genética , Neoplasias do Colo do Útero/patologia
16.
Oncology ; 98(8): 583-588, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32521533

RESUMO

BACKGROUND: Gastric cancer (GC) is one of the leading causes of cancer death in China, while the nature of genetic factors related to GC has not been well-studied. OBJECTIVES: To assess the inherited genetic factors regarding pathogenic germline mutations in Chinese GC population. METHODS: Genomic profiling of DNA was performed through next-generation sequencing with 381 cancer-related genes on tissue from patients with GC between January 1, 2017, and May 7, 2019. RESULTS: 470 GC patients were included for analysis. A total of 28 (6.0%) patients were identified to harbor 25 different pathogenic or very likely pathogenic germline mutations in 15 genes. The variants fell most frequently in BRCA2 (n = 6, 1.28%), CHEK2 (n = 5, 1.06%), MUTYH (n = 3, 0.64%), CDH1 (n = 2, 0.43%), and ATM (n = 2, 0.43%). Of all the germline-mutated genes, 66.7% (n = 10) lay in the DNA damage repair pathways. Seven patients were identified to have a high TMB status, among whom two were also identified as MSI-H. Overall, 20 out of the 28 patients (71.4%) carried clinically actionable mutations. CONCLUSIONS: Our study has depicted the spectrum of pathogenic germline mutations in Chinese GC patients, which may provide valuable clues for the assessment of the genetic susceptibility and clinical management in GC.


Assuntos
Mutação em Linhagem Germinativa , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Neoplasias Gástricas/epidemiologia , Neoplasias Gástricas/genética , Idoso , Proteína BRCA2/genética , Quinase do Ponto de Checagem 2/genética , China/epidemiologia , Dano ao DNA/genética , DNA Glicosilases/genética , Feminino , Predisposição Genética para Doença , Humanos , Masculino , Instabilidade de Microssatélites , Pessoa de Meia-Idade , Neoplasias Gástricas/patologia
17.
Nat Commun ; 11(1): 2950, 2020 06 11.
Artigo em Inglês | MEDLINE | ID: mdl-32528002

RESUMO

During homologous recombination, Rad51 forms a nucleoprotein filament on single-stranded DNA to promote DNA strand exchange. This filament binds to double-stranded DNA (dsDNA), searches for homology, and promotes transfer of the complementary strand, producing a new heteroduplex. Strand exchange proceeds via two distinct three-strand intermediates, C1 and C2. C1 contains the intact donor dsDNA whereas C2 contains newly formed heteroduplex DNA. Here, we show that the conserved DNA binding motifs, loop 1 (L1) and loop 2 (L2) in site I of Rad51, play distinct roles in this process. L1 is involved in formation of the C1 complex whereas L2 mediates the C1-C2 transition, producing the heteroduplex. Another DNA binding motif, site II, serves as the DNA entry position for initial Rad51 filament formation, as well as for donor dsDNA incorporation. Our study provides a comprehensive molecular model for the catalytic process of strand exchange mediated by eukaryotic RecA-family recombinases.


Assuntos
DNA/metabolismo , Rad51 Recombinase/química , Rad51 Recombinase/metabolismo , Trifosfato de Adenosina/metabolismo , Sítios de Ligação/genética , DNA/genética , Dano ao DNA/genética , Dano ao DNA/fisiologia , Reparo do DNA/genética , Reparo do DNA/fisiologia , DNA de Cadeia Simples/genética , Recombinação Homóloga/genética , Recombinação Homóloga/fisiologia , Humanos , Mutação/genética , Ácidos Nucleicos Heteroduplexes/genética , Ácidos Nucleicos Heteroduplexes/metabolismo , Estrutura Secundária de Proteína , Rad51 Recombinase/genética , Saccharomyces cerevisiae/genética , Schizosaccharomyces/genética
18.
Nucleic Acids Res ; 48(12): 6715-6725, 2020 07 09.
Artigo em Inglês | MEDLINE | ID: mdl-32484547

RESUMO

DNA damage and epigenetic marks are well established to have profound influences on genome stability and cell phenotype, yet there are few technologies to obtain high-resolution genomic maps of the many types of chemical modifications of DNA. Here we present Nick-seq for quantitative, sensitive, and accurate mapping of DNA modifications at single-nucleotide resolution across genomes. Pre-existing breaks are first blocked and DNA modifications are then converted enzymatically or chemically to strand-breaks for both 3'-extension by nick-translation to produce nuclease-resistant oligonucleotides and 3'-terminal transferase tailing. Following library preparation and next generation sequencing, the complementary datasets are mined with a custom workflow to increase sensitivity, specificity and accuracy of the map. The utility of Nick-seq is demonstrated with genomic maps of site-specific endonuclease strand-breaks in purified DNA from Eschericia coli, phosphorothioate epigenetics in Salmonella enterica Cerro 87, and oxidation-induced abasic sites in DNA from E. coli treated with a sublethal dose of hydrogen peroxide. Nick-seq applicability is demonstrated with strategies for >25 types of DNA modification and damage.


Assuntos
Dano ao DNA/efeitos dos fármacos , Epigênese Genética/genética , Genoma Bacteriano/genética , Instabilidade Genômica/efeitos dos fármacos , Mapeamento Cromossômico , DNA/química , DNA/efeitos dos fármacos , Dano ao DNA/genética , Escherichia coli/genética , Genoma Bacteriano/efeitos dos fármacos , Sequenciamento de Nucleotídeos em Larga Escala , Peróxido de Hidrogênio/toxicidade , Nucleotídeos/química , Salmonella enterica/genética , Análise de Sequência de DNA
19.
Mol Cell ; 78(6): 1045-1054, 2020 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-32516599

RESUMO

Cell death, or, more specifically, cell suicide, is a process of fundamental importance to human health. Throughout our lives, over a million cells are produced every second. When organismal growth has stopped, to balance cell division, a similar number of cells must be removed. This is achieved by activation of molecular mechanisms that have evolved so that cells can destroy themselves. The first clues regarding the nature of one of these mechanisms came from studying genes associated with cancer, in particular the gene for BCL-2. Subsequent studies revealed that mutations or other defects that inhibit cell death allow cells to accumulate, prevent removal of cells with damaged DNA, and increase the resistance of malignant cells to chemotherapy. Knowledge of this mechanism has allowed development of drugs that kill cancer cells by directly activating the cell death machinery and by synergizing with conventional chemotherapy as well as targeted agents to achieve improved outcomes for cancer patients.


Assuntos
Morte Celular/fisiologia , Neoplasias/genética , Neoplasias/terapia , Apoptose/genética , Morte Celular/genética , Dano ao DNA/genética , Humanos , Neoplasias/fisiopatologia
20.
Ecotoxicol Environ Saf ; 201: 110737, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32505758

RESUMO

Macrolide antibiotics are common contaminants in the aquatic environment. They are toxic to a wide range of primary producers, inhibiting the algal growth and further hindering the delivery of several ecosystem services. Yet the molecular mechanisms of macrolides in algae remain undetermined. The objectives of this study were therefore to: 1. evaluate whether macrolides at the environmentally relevant level inhibit the growth of algae; and 2. test the hypothesis that macrolides bind to ribosome and inhibit protein translocation in algae, as it does in bacteria. In this study, transcriptomic analysis was applied to elucidate the toxicological mechanism in a model green alga Raphidocelis subcapitata treated with 5 and 90 µg L-1 of a typical macrolide roxithromycin (ROX). While exposure to ROX at 5 µg L-1 for 7 days did not affect algal growth and the transciptome, ROX at 90 µg L-1 resulted in 45% growth inhibition and 2306 (983 up- and 1323 down-regulated) DEGs, which were primarily enriched in the metabolism of energy, lipid, vitamins, and DNA replication and repair pathways. Nevertheless, genes involved in pathways in relation to translation and protein translocation and processing were dysregulated. Surprisingly, we found that genes involved in the base excision repair process were mostly repressed, suggesting that ROX may be genotoxic and cause DNA damage in R. subcapitata. Taken together, ROX was unlikely to pose a threat to green algae in the environment and the mode of action of macrolides in bacteria may not be directly extrapolated to green algae.


Assuntos
Antibacterianos/toxicidade , Clorofíceas/efeitos dos fármacos , Reparo do DNA/efeitos dos fármacos , Roxitromicina/toxicidade , Poluentes Químicos da Água/toxicidade , Clorofíceas/genética , Clorofíceas/crescimento & desenvolvimento , Dano ao DNA/genética , Reparo do DNA/genética , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Transcriptoma/efeitos dos fármacos
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