RESUMO
Genome instability relies on preserving the chromatin structure, with any histone imbalances threating DNA integrity. Histone synthesis occurs in the cytoplasm, followed by a maturation process before their nuclear translocation. This maturation involves protein folding and the establishment of post-translational modifications. Disruptions in this pathway hinder chromatin assembly and contribute to genome instability. JMJD1B, a histone demethylase, not only regulates gene expression but also ensures a proper supply of histones H3 and H4 for the chromatin assembly. Reduced JMJD1B levels lead to the cytoplasmic accumulation of histones, causing defects in the chromatin assembly and resulting in DNA damage. To investigate the role of JMJD1B in regulating genome stability and the malignancy of melanoma tumors, we used a JMJD1B/KDM3B knockout in B16F10 mouse melanoma cells to perform tumorigenic and genome instability assays. Additionally, we analyzed the transcriptomic data of human cutaneous melanoma tumors. Our results show the enhanced tumorigenic properties of JMJD1B knockout melanoma cells both in vitro and in vivo. The γH2AX staining, Micrococcal Nuclease sensitivity, and comet assays demonstrated increased DNA damage and genome instability. The JMJD1B expression in human melanoma tumors correlates with a lower mutational burden and fewer oncogenic driver mutations. Our findings highlight JMJD1B's role in maintaining genome integrity by ensuring a proper histone supply to the nucleus, expanding its function beyond gene expression regulation. JMJD1B emerges as a crucial player in preserving genome stability and the development of melanoma, with a potential role as a safeguard against oncogenic mutations.
Assuntos
Dano ao DNA , Instabilidade Genômica , Histonas , Histona Desmetilases com o Domínio Jumonji , Melanoma , Neoplasias Cutâneas , Animais , Humanos , Camundongos , Linhagem Celular Tumoral , Dano ao DNA/genética , Regulação Neoplásica da Expressão Gênica , Histonas/metabolismo , Histona Desmetilases com o Domínio Jumonji/metabolismo , Histona Desmetilases com o Domínio Jumonji/genética , Melanoma/genética , Melanoma/patologia , Melanoma/metabolismo , Melanoma Experimental/genética , Melanoma Experimental/patologia , Melanoma Experimental/metabolismo , Neoplasias Cutâneas/genética , Neoplasias Cutâneas/patologia , Neoplasias Cutâneas/metabolismoRESUMO
There are extensive studies on chromosome morphology and karyotype diversity in primates, yet we still lack insight into genomic instability as a key factor underlying the enormous interspecies chromosomal variability and its potential contribution to evolutionary dynamics. In this sense, the assessment of spontaneous sister chromatid exchange (SCE) frequencies represents a powerful tool for evaluating genome stability. Here, we employed G-banding, fluorescence plus Giemsa (FPG), and chromosome orientation fluorescence in situ hybridization (CO-FISH) methodologies to characterize both chromosome-specific frequencies of spontaneously occurring SCE throughout the genome (G-SCE) and telomere-specific SCE (T-SCE). We analyzed primary fibroblast cultures from two male species of Ateles living in captivity: Ateles paniscus (APA) and Ateles chamek (ACH). High frequencies of G-SCEs were observed in both species. Interestingly, G-SCEs clustered on evolutionary relevant chromosome pairs: ACH chromosomes 1, 2, 3, 4, and 7, and APA chromosomes 1, 2, 3, 4/12, 7, and 10. Furthermore, a statistically significant difference between the observed and expected G-SCE frequencies, not correlated with chromosome size, was also detected. CO-FISH analyses revealed the presence of telomere-specific recombination events in both species, which included T-SCE, as well as interstitial telomere signals and telomere duplications, with APA chromosomes displaying higher frequencies, compared to ACH. Our analyses support the hypothesis that regions of Ateles chromosomes susceptible to recombination events are fragile sites and evolutionary hot spots. Thus, we propose SCE analyses as a valuable indicator of genome instability in non-human primates.
RESUMO
Pathogen fitness landscapes change when transmission cycles establish in non-native environments or spill over into new vectors and hosts. The introduction of Leishmania infantum in the Americas into the Neotropics during European colonization represents a unique case study to investigate the mechanisms of ecological adaptation of this important parasite. Defining the evolutionary trajectories that drive L. infantum fitness in this new environment are of great public health importance as they will allow unique insight into pathways of host/pathogen co-evolution and their consequences for region-specific changes in disease manifestation. This review summarizes current knowledge on L. infantum genetic and phenotypic diversity in the Americas and its possible role in the unique epidemiology of visceral leishmaniasis (VL) in the New World. We highlight the importance of appreciating adaptive molecular mechanisms in L. infantum to understand the parasites' successful establishment on the continent.
Assuntos
Leishmania infantum/classificação , Leishmaniose Visceral/transmissão , Oceano Atlântico , Evolução Molecular , Aptidão Genética , Humanos , Leishmania infantum/genética , FenótipoRESUMO
Tumorigenesis is a multistep process involving genetic and epigenetic alterations that drive somatic evolution from normal human cells to malignant derivatives. Collectively, genetic and epigenetic alterations might be combined into biomarkers for the assessment of risk, the detection of early stage tumors, and accurate tumor characterization before and after treatment. Recent efforts have provided systematic approaches to cancer genomics through the application of massive sequencing of specific tumor types. Here, we review biomarkers of genome instability and epigenetics. Cancer evolvability and adaptation emerge through genetic and epigenetic lesions of a variety of sizes and qualities-from point mutations and small insertions/deletions to large-scale chromosomal rearrangements, alterations in whole chromosome copy number, preferential allelic expression of cancer risk alleles, and mechanisms that increase tumor mutation rates. We also review specific epigenetic mechanisms that facilitate or hinder tumor adaptation, including DNA methylation, histone modification, nucleosome remodeling, transcription factor activity, and small non-coding RNAs. Given the complexity of the carcinogenic process, the challenge ahead will be to interpret disparate signals across hundreds of genes and summarize these signals into a single actionable diagnosis that translates into specific treatments. Another challenge is to refine preventive efforts through the identification of epigenetic processes that mediate increased cancer rates in individuals exposed to sources of toxic environmental stress and pollution, specially through development and early childhood.
Assuntos
Biomarcadores/análise , Epigênese Genética , Instabilidade Genômica , Neoplasias/diagnóstico , Neoplasias/genética , HumanosRESUMO
Genome instability is observed in several species hybrids. We studied the mechanisms underlying the genome instability in hexaploid hybrids of Napier grass (Pennisetum purpureum R.) and pearl millet (Pennisetum glaucum L.) using a combination of different methods. Chromosomes of both parental genomes are lost by micronucleation. Our analysis suggests that genome instability occurs preferentially in meristematic root tissue of hexaploid hybrids, and chromosome elimination is not only caused by centromere inactivation. Likely, beside centromere dysfunction, unrepaired DNA double-strand breaks result in fragmented chromosomes in synthetic hybrids.
Assuntos
Centrômero/metabolismo , Cromossomos de Plantas/genética , Instabilidade Genômica/genética , Meristema/genética , Pennisetum/genética , Raízes de Plantas/genética , Quimera/genética , Quebras de DNA de Cadeia Dupla , Hibridização Genética , Hibridização in Situ Fluorescente , Micronúcleos com Defeito Cromossômico , Melhoramento Vegetal , PoliploidiaRESUMO
Tyrosyl-DNA-phosphodiesterase 1 (TDP1) is a DNA repair enzyme that removes irreversible protein-linked 3' DNA complexes, 3' phosphoglycolates, alkylation damage-induced DNA breaks, and 3' deoxyribose nucleosides. In addition to its extended spectrum of substrates, TDP1 interacts with several DNA damage response factors. To determine whether TDP1 participates in the repair of topoisomerase II (Top2) induced DNA lesions, we generated TDP1 depleted (TDP1kd) human tumoral cells. We found that TDP1kd cells are hypersensitive to etoposide (ETO). Moreover, we established in a chromatin context that following treatment with ETO, TDP1kd cells accumulate increased amounts of Top2α cleavage complexes, removing them with an altered kinetics. We also showed that TDP1 depleted cells accumulate increased γH2AX and pS296Chk1 signals following treatment with ETO. Similarly, cytogenetics analyses following Top2 poisoning revealed increased amounts of chromatid and chromosome breaks and exchanges on TDP1kd cells in the presence or not of the DNA-PKcs inhibitor NU7026. However, the levels of sister chromatid exchanges were similar in both TDP1kd and control non-silenced cell lines. This suggests a role of TDP1 in both canonical non-homologous end joining and alternative end joining, but not in the homologous recombination repair pathway. Finally, micronucleus analyses following ETO treatment revealed a higher frequency of micronucleus containing γH2AX signals on TDP1kd cells. Together, our results highlight an active role of TDP1 in the repair of Top2-induced DNA damage and its relevance on the genome stability maintenance in human cells.
Assuntos
Antígenos de Neoplasias/toxicidade , Dano ao DNA/genética , Reparo do DNA por Junção de Extremidades/genética , DNA Topoisomerases Tipo II/toxicidade , Proteínas de Ligação a DNA/toxicidade , Diester Fosfórico Hidrolases/metabolismo , Cromonas , Ensaio de Unidades Formadoras de Colônias , Reparo do DNA por Junção de Extremidades/fisiologia , Primers do DNA/genética , Etoposídeo/farmacologia , Citometria de Fluxo , Imunofluorescência , Violeta Genciana , Células HeLa , Histonas/metabolismo , Humanos , Immunoblotting , Testes para Micronúcleos , Morfolinas , Diester Fosfórico Hidrolases/deficiência , Diester Fosfórico Hidrolases/genética , Proteínas de Ligação a Poli-ADP-Ribose , Reação em Cadeia da Polimerase em Tempo RealRESUMO
Mitochondrial dysfunction is regarded as a hallmark of cancer progression. In the current study, we evaluated mitochondrial genome instability and copy number in colorectal cancer using Next Generation Sequencing approach and qPCR, respectively. The results revealed higher levels of heteroplasmy and depletion of the relative mtDNA copy number in colorectal adenocarcinoma. Adenocarcinoma samples also presented an increased number of mutations in nuclear genes encoding proteins which functions are related with mitochondria fusion, fission and localization. Moreover, we found a set of mitochondrial and nuclear genes, which cooperate in the same mitochondrial function simultaneously mutated in adenocarcinoma. In summary, these results support an important role for mitochondrial function and genomic instability in colorectal tumorigenesis.