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1.
Nat Cell Biol ; 23(2): 160-171, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33462394

RESUMO

The response to poly(ADP-ribose) polymerase inhibitors (PARPi) is dictated by homologous recombination (HR) DNA repair and the abundance of lesions that trap PARP enzymes. It remains unclear, however, if the established role of PARP in promoting chromatin accessibility impacts viability in these settings. Using a CRISPR-based screen, we identified the PAR-binding chromatin remodeller ALC1/CHD1L as a key determinant of PARPi toxicity in HR-deficient cells. ALC1 loss reduced viability of breast cancer gene (BRCA)-mutant cells and enhanced sensitivity to PARPi by up to 250-fold, while overcoming several resistance mechanisms. ALC1 deficiency reduced chromatin accessibility concomitant with a decrease in the association of base damage repair factors. This resulted in an accumulation of replication-associated DNA damage, increased PARP trapping and a reliance on HR. These findings establish PAR-dependent chromatin remodelling as a mechanistically distinct aspect of PARPi responses and therapeutic target in HR-deficient cancers.


Assuntos
Cromatina/metabolismo , DNA Helicases/metabolismo , Proteínas de Ligação a DNA/metabolismo , Recombinação Homóloga/genética , Inibidores de Poli(ADP-Ribose) Polimerases/farmacologia , Proteína BRCA1/genética , Proteína BRCA2/genética , Sistemas CRISPR-Cas/genética , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Montagem e Desmontagem da Cromatina/efeitos dos fármacos , Aberrações Cromossômicas , DNA Helicases/química , Reparo do DNA/efeitos dos fármacos , Proteínas de Ligação a DNA/química , Epistasia Genética/efeitos dos fármacos , Instabilidade Genômica , Proteínas de Fluorescência Verde/metabolismo , Recombinação Homóloga/efeitos dos fármacos , Humanos , Metanossulfonato de Metila , Mutação/genética , Ftalazinas/farmacologia , Piperazinas/farmacologia , Poli Adenosina Difosfato Ribose/metabolismo , Poli(ADP-Ribose) Polimerases/metabolismo , Domínios Proteicos
2.
Ginebra; European Society for Medical Oncology; 2020; Sept. 28, 2020. 17 p.
Monografia em Inglês | BIGG - guias GRADE | ID: biblio-1127783

RESUMO

The European Society for Medical Oncology (ESMO) Translational Research and Precision Medicine Working Group identified that there is currently uncertainty within the oncology community surrounding the different methods for HRD testing in HGSC. To address this, a collaborative project was launched with a number of clinicians and scientists with expertise in the fields of PARPi clinical trials, cancer genomics and DNA repair. The group defined three main aims for the project: (i) Define the term 'HRD test' and recommend how an HRD test's clinical validity is currently best assessed in the context of HGSC, (ii) provide an overview of the biological rationale and the level of evidence supporting currently available HRD tests, and (iii) provide recommendations on the clinical utility of HRD tests in clinical management of HGSC.


Assuntos
Humanos , Feminino , Biomarcadores , Neoplasias dos Genitais Femininos/diagnóstico , Mutação em Linhagem Germinativa/genética , Recombinação Homóloga/genética , Inibidores de Poli(ADP-Ribose) Polimerases/uso terapêutico
3.
Nucleic Acids Res ; 48(16): 9147-9160, 2020 09 18.
Artigo em Inglês | MEDLINE | ID: mdl-32749454

RESUMO

DNA topoisomerase II (TOP2) is a major DNA metabolic enzyme, with important roles in replication, transcription, chromosome segregation and spatial organisation of the genome. TOP2 is the target of a class of anticancer drugs that poison the DNA-TOP2 transient complex to generate TOP2-linked DNA double-strand breaks (DSBs). The accumulation of DSBs kills tumour cells but can also result in genome instability. The way in which topoisomerase activity contributes to transcription remains unclear. In this work we have investigated how transcription contributes to TOP2-dependent DSB formation, genome instability and cell death. Our results demonstrate that gene transcription is an important source of abortive TOP2 activity. However, transcription does not contribute significantly to apoptosis or cell death promoted by TOP2-induced DSBs. On the contrary: transcription-dependent breaks greatly contribute to deleterious mutations and translocations, and can promote oncogenic rearrangements. Importantly, we show that TOP2-induced genome instability is mediated by mutagenic canonical non-homologous end joining whereas homologous recombination protects cells against these insults. Collectively, these results uncover mechanisms behind deleterious effects of TOP2 abortive activity during transcription, with relevant implications for chemotherapy.


Assuntos
Reparo do DNA por Junção de Extremidades/genética , DNA Topoisomerases Tipo II/genética , Recombinação Homóloga/genética , Translocação Genética , DNA/genética , Quebras de DNA de Cadeia Dupla , Dano ao DNA/genética , Proteínas de Ligação a DNA/genética , Instabilidade Genômica/genética , Humanos , Mutagênese/genética , Fatores de Transcrição/genética
4.
Nucleic Acids Res ; 48(16): 9135-9146, 2020 09 18.
Artigo em Inglês | MEDLINE | ID: mdl-32735676

RESUMO

Microcephalin 1 (MCPH1) was identified from genetic mutations in patients with primary autosomal recessive microcephaly. In response to DNA double-strand breaks (DSBs), MCPH1 forms damage-induced foci and recruits BRCA2-RAD51 complex, a key component of the DSB repair machinery for homologous recombination (HR), to damage sites. Accordingly, the efficiency of HR is significantly attenuated upon depletion of MCPH1. The biochemical characteristics of MCPH1 and its functional interaction with the HR machinery had remained unclear due to lack of highly purified MCPH1 recombinant protein for functional study. Here, we established a mammalian expression system to express and purify MCPH1 protein. We show that MCPH1 is a bona fide DNA-binding protein and provide direct biochemical analysis of this MCPH family protein. Furthermore, we reveal that MCPH1 directly interacts with RAD51 at multiple contact points, providing evidence for how MCPH1 physically engages with the HR machinery. Importantly, we demonstrate that MCPH1 enhances the stability of RAD51 on single-strand DNA, a prerequisite step for RAD51-mediated recombination. Single-molecule tethered particle motion analysis showed a ∼2-fold increase in the lifetime of RAD51-ssDNA filaments in the presence of MCPH1. Thus, our study demonstrates direct crosstalk between microcephaly protein MCPH1 and the recombination component RAD51 for DSB repair.


Assuntos
Proteína BRCA2/genética , Proteínas de Ciclo Celular/genética , Proteínas do Citoesqueleto/genética , Microcefalia/genética , Rad51 Recombinase/genética , Citoesqueleto/genética , Quebras de DNA de Cadeia Dupla , Dano ao DNA/genética , Reparo do DNA/genética , DNA de Cadeia Simples/genética , Proteínas de Ligação a DNA/genética , Instabilidade Genômica/genética , Recombinação Homóloga/genética , Humanos , Microcefalia/patologia , Nucleoproteínas/genética
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.
Sci Rep ; 10(1): 12235, 2020 07 22.
Artigo em Inglês | MEDLINE | ID: mdl-32699385

RESUMO

The most prevalent microdeletion in humans occurs at 22q11.2, a region rich in chromosome-specific low copy repeats (LCR22s). The structure of this region has defied elucidation due to its size, regional complexity, and haplotype diversity, and is not well represented in the human genome reference. Most individuals with 22q11.2 deletion syndrome (22q11.2DS) carry a de novo hemizygous deletion of ~ 3 Mbp occurring by non-allelic homologous recombination (NAHR) mediated by LCR22s. In this study, optical mapping has been used to elucidate LCR22 structure and variation in 88 individuals in thirty 22q11.2DS families to uncover potential risk factors for germline rearrangements leading to 22q11.2DS offspring. Families were optically mapped to characterize LCR22 structures, NAHR locations, and genomic signatures associated with the deletion. Bioinformatics analyses revealed clear delineations between LCR22 structures in normal and deletion-containing haplotypes. Despite no explicit whole-haplotype predisposing configurations being identified, all NAHR events contain a segmental duplication encompassing FAM230 gene members suggesting preferred recombination sequences. Analysis of deletion breakpoints indicates that preferred recombinations occur between FAM230 and specific segmental duplication orientations within LCR22A and LCR22D, ultimately leading to NAHR. This work represents the most comprehensive analysis of 22q11.2DS NAHR events demonstrating completely contiguous LCR22 structures surrounding and within deletion breakpoints.


Assuntos
Cromossomos Humanos Par 22/genética , Síndrome de DiGeorge/genética , Recombinação Homóloga/genética , Duplicações Segmentares Genômicas/genética , Alelos , Deleção Cromossômica , Mapeamento Cromossômico/métodos , Feminino , Genoma Humano/genética , Haplótipos/genética , Humanos , Masculino
7.
Nat Commun ; 11(1): 3088, 2020 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-32555206

RESUMO

DNA double-strand break repair by homologous recombination begins with nucleolytic resection of the 5' DNA strand at the break ends. Long-range resection is catalyzed by EXO1 and BLM-DNA2, which likely have to navigate through ribonucleotides and damaged bases. Here, we show that a short stretch of ribonucleotides at the 5' terminus stimulates resection by EXO1. Ribonucleotides within a 5' flap are resistant to cleavage by DNA2, and extended RNA:DNA hybrids inhibit both strand separation by BLM and resection by EXO1. Moreover, 8-oxo-guanine impedes EXO1 but enhances resection by BLM-DNA2, and an apurinic/apyrimidinic site stimulates resection by BLM-DNA2 and DNA strand unwinding by BLM. Accordingly, depletion of OGG1 or APE1 leads to greater dependence of DNA resection on DNA2. Importantly, RNase H2A deficiency impairs resection overall, which we attribute to the accumulation of long RNA:DNA hybrids at DNA ends. Our results help explain why eukaryotic cells possess multiple resection nucleases.


Assuntos
Quebras de DNA de Cadeia Dupla , Ribonucleotídeos/genética , Ribonucleotídeos/metabolismo , Western Blotting , Linhagem Celular Tumoral , DNA Glicosilases/genética , Enzimas Reparadoras do DNA/genética , DNA Liase (Sítios Apurínicos ou Apirimidínicos)/genética , Exodesoxirribonucleases/genética , Imunofluorescência , Recombinação Homóloga/genética , Humanos , RecQ Helicases/genética , Recombinação Genética/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo
8.
Nat Commun ; 11(1): 3101, 2020 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-32555348

RESUMO

Orderly chromosome segregation is enabled by crossovers between homologous chromosomes in the first meiotic division. Crossovers arise from recombination-mediated repair of programmed DNA double-strand breaks (DSBs). Multiple DSBs initiate recombination, and most are repaired without crossover formation, although one or more generate crossovers on each chromosome. Although the underlying mechanisms are ill-defined, the differentiation and maturation of crossover-specific recombination intermediates requires the cyclin-like CNTD1. Here, we identify PRR19 as a partner of CNTD1. We find that, like CNTD1, PRR19 is required for timely DSB repair and the formation of crossover-specific recombination complexes. PRR19 and CNTD1 co-localise at crossover sites, physically interact, and are interdependent for accumulation, indicating a PRR19-CNTD1 partnership in crossing over. Further, we show that CNTD1 interacts with a cyclin-dependent kinase, CDK2, which also accumulates in crossover-specific recombination complexes. Thus, the PRR19-CNTD1 complex may enable crossover differentiation by regulating CDK2.


Assuntos
Troca Genética/genética , Ciclinas/genética , Quebras de DNA de Cadeia Dupla , Meiose/genética , Animais , Cromossomos/genética , Quinase 2 Dependente de Ciclina/genética , Dano ao DNA/genética , Reparo do DNA/genética , Feminino , Recombinação Homóloga/genética , Masculino , Camundongos
9.
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
10.
Mol Cell ; 78(5): 951-959.e6, 2020 06 04.
Artigo em Inglês | MEDLINE | ID: mdl-32359443

RESUMO

BRCA1 promotes the DNA end resection and RAD51 loading steps of homologous recombination (HR). Whether these functions can be uncoupled, and whether mutant proteins retaining partial activity can complement one another, is unclear and could affect the severity of BRCA1-associated Fanconi anemia (FA). Here we generated a Brca1CC mouse with a coiled-coil (CC) domain deletion. Brca1CC/CC mice are born at low frequencies, and post-natal mice have FA-like abnormalities, including bone marrow failure. Intercrossing with Brca1Δ11, which is homozygous lethal, generated Brca1CC/Δ11 mice at Mendelian frequencies that were indistinguishable from Brca1+/+ mice. Brca1CC and Brca1Δ11 proteins were individually responsible for counteracting 53BP1-RIF1-Shieldin activity and promoting RAD51 loading, respectively. Thus, Brca1CC and Brca1Δ11 alleles represent separation-of-function mutations that combine to provide a level of HR sufficient for normal development and hematopoiesis. Because BRCA1 activities can be genetically separated, compound heterozygosity for functional complementary mutations may protect individuals from FA.


Assuntos
Proteína BRCA1/genética , Recombinação Homóloga/genética , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Animais , Proteína BRCA1/metabolismo , Quebras de DNA de Cadeia Dupla , Reparo do DNA , Éxons , Anemia de Fanconi/genética , Anemia de Fanconi/metabolismo , Feminino , Células HEK293 , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C3H , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mutação , Rad51 Recombinase/genética , Rad51 Recombinase/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo
11.
Mol Cell ; 78(6): 1252-1263.e3, 2020 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-32362315

RESUMO

Crossover recombination is critical for meiotic chromosome segregation, but how mammalian crossing over is accomplished is poorly understood. Here, we illuminate how strands exchange during meiotic recombination in male mice by analyzing patterns of heteroduplex DNA in recombinant molecules preserved by the mismatch correction deficiency of Msh2-/- mutants. Surprisingly, MSH2-dependent recombination suppression was not evident. However, a substantial fraction of crossover products retained heteroduplex DNA, and some provided evidence of MSH2-independent correction. Biased crossover resolution was observed, consistent with asymmetry between DNA ends in earlier intermediates. Many crossover products yielded no heteroduplex DNA, suggesting dismantling by D-loop migration. Unlike the complexity of crossovers in yeast, these simple modifications of the original double-strand break repair model-asymmetry in recombination intermediates and D-loop migration-may be sufficient to explain most meiotic crossing over in mice while also addressing long-standing questions related to Holliday junction resolution.


Assuntos
Troca Genética/fisiologia , Recombinação Homóloga/fisiologia , Meiose/fisiologia , Animais , Segregação de Cromossomos/genética , Troca Genética/genética , Quebras de DNA de Cadeia Dupla , Reparo do DNA/genética , DNA Cruciforme/genética , DNA Cruciforme/metabolismo , Recombinação Homóloga/genética , Masculino , Meiose/genética , Camundongos , Camundongos Endogâmicos DBA , Proteína 2 Homóloga a MutS/genética , Proteína 2 Homóloga a MutS/metabolismo , Ácidos Nucleicos Heteroduplexes/genética
12.
BMC Evol Biol ; 20(1): 52, 2020 05 07.
Artigo em Inglês | MEDLINE | ID: mdl-32381044

RESUMO

BACKGROUND: A frequent event in the evolution of prokaryotic genomes is homologous recombination, where a foreign DNA stretch replaces a genomic region similar in sequence. Recombination can affect the relative position of two genomes in a phylogenetic reconstruction in two different ways: (i) one genome can recombine with a DNA stretch that is similar to the other genome, thereby reducing their pairwise sequence divergence; (ii) one genome can recombine with a DNA stretch from an outgroup genome, increasing the pairwise divergence. While several recombination-aware phylogenetic algorithms exist, many of these cannot account for both types of recombination; some algorithms can, but do so inefficiently. Moreover, many of them reconstruct the ancestral recombination graph (ARG) to help infer the genome tree, and require that a substantial portion of each genome has not been affected by recombination, a sometimes unrealistic assumption. METHODS: Here, we propose a Coarse-Graining approach for Phylogenetic reconstruction (CGP), which is recombination-aware but forgoes ARG reconstruction. It accounts for the tendency of a higher effective recombination rate between genomes with a lower phylogenetic distance. It is applicable even if all genomic regions have experienced substantial amounts of recombination, and can be used on both nucleotide and amino acid sequences. CGP considers the local density of substitutions along pairwise genome alignments, fitting a model to the empirical distribution of substitution density to infer the pairwise coalescent time. Given all pairwise coalescent times, CGP reconstructs an ultrametric tree representing vertical inheritance. RESULTS: Based on simulations, we show that the proposed approach can reconstruct ultrametric trees with accurate topology, branch lengths, and root positioning. Applied to a set of E. coli strains, the reconstructed trees are most consistent with gene distributions when inferred from amino acid sequences, a data type that cannot be utilized by many alternative approaches. CONCLUSIONS: The CGP algorithm is more accurate than alternative recombination-aware methods for ultrametric phylogenetic reconstructions.


Assuntos
Algoritmos , Recombinação Homóloga/genética , Filogenia , Células Procarióticas/metabolismo , Simulação por Computador , Bases de Dados Genéticas , Escherichia coli/genética , Genoma Bacteriano , Funções Verossimilhança , Modelos Genéticos , Shigella/genética
13.
Genes Dev ; 34(11-12): 832-846, 2020 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-32354836

RESUMO

DNA interstrand cross-links (ICLs) are a form of DNA damage that requires the interplay of a number of repair proteins including those of the Fanconi anemia (FA) and the homologous recombination (HR) pathways. Pathogenic variants in the essential gene BRCA2/FANCD1, when monoallelic, predispose to breast and ovarian cancer, and when biallelic, result in a severe subtype of Fanconi anemia. BRCA2 function in the FA pathway is attributed to its role as a mediator of the RAD51 recombinase in HR repair of programmed DNA double-strand breaks (DSB). BRCA2 and RAD51 functions are also required to protect stalled replication forks from nucleolytic degradation during response to hydroxyurea (HU). While RAD51 has been shown to be necessary in the early steps of ICL repair to prevent aberrant nuclease resection, the role of BRCA2 in this process has not been described. Here, based on the analysis of BRCA2 DNA-binding domain (DBD) mutants (c.8488-1G>A and c.8524C>T) discovered in FA patients presenting with atypical FA-like phenotypes, we establish that BRCA2 is necessary for the protection of DNA at ICLs. Cells carrying BRCA2 DBD mutations are sensitive to ICL-inducing agents but resistant to HU treatment consistent with relatively high HR repair in these cells. BRCA2 function at an ICL protects against DNA2-WRN nuclease-helicase complex and not the MRE11 nuclease that is implicated in the resection of HU-induced stalled replication forks. Our results also indicate that unlike the processing at HU-induced stalled forks, the function of the SNF2 translocases (SMARCAL1, ZRANB3, or HLTF), implicated in fork reversal, are not an integral component of the ICL repair, pointing to a different mechanism of fork protection at different DNA lesions.


Assuntos
Proteína BRCA2/metabolismo , Anemia de Fanconi/genética , Anemia de Fanconi/fisiopatologia , Proteína BRCA2/genética , Linhagem Celular , DNA/química , Reparo do DNA/efeitos dos fármacos , Reparo do DNA/genética , Replicação do DNA/efeitos dos fármacos , Recombinação Homóloga/genética , Humanos , Hidroxiureia/farmacologia , Mutação , Domínios Proteicos/genética , Rad51 Recombinase/metabolismo
14.
Nucleic Acids Res ; 48(12): 6624-6639, 2020 07 09.
Artigo em Inglês | MEDLINE | ID: mdl-32463460

RESUMO

Repair of DNA double-strand breaks (DSBs) with homologous chromosomes is a hallmark of meiosis that is mediated by recombination 'bridges' between homolog axes. This process requires cooperation of DMC1 and RAD51 to promote homology search and strand exchange. The mechanism(s) regulating DMC1/RAD51-ssDNA nucleoprotein filament and the components of 'bridges' remain to be investigated. Here we show that MEIOK21 is a newly identified component of meiotic recombination bridges and is required for efficient formation of DMC1/RAD51 foci. MEIOK21 dynamically localizes on chromosomes from on-axis foci to 'hanging foci', then to 'bridges', and finally to 'fused foci' between homolog axes. Its chromosome localization depends on DSBs. Knockout of Meiok21 decreases the numbers of HSF2BP and DMC1/RAD51 foci, disrupting DSB repair, synapsis and crossover recombination and finally causing male infertility. Therefore, MEIOK21 is a novel recombination factor and probably mediates DMC1/RAD51 recruitment to ssDNA or their stability on chromosomes through physical interaction with HSF2BP.


Assuntos
Proteínas de Ciclo Celular/genética , Proteínas de Ligação a DNA/genética , Recombinação Homóloga/genética , Infertilidade Masculina/genética , Espermatogênese/genética , Animais , Proteínas de Transporte/genética , Pareamento Cromossômico/genética , Cromossomos/genética , Quebras de DNA de Cadeia Dupla , Reparo do DNA/genética , DNA de Cadeia Simples/genética , Técnicas de Inativação de Genes , Proteínas de Choque Térmico/genética , Masculino , Meiose/genética , Camundongos , Camundongos Knockout , Proteínas de Ligação a Fosfato/genética , Rad51 Recombinase/genética
15.
Cell Physiol Biochem ; 54(3): 354-370, 2020 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-32298553

RESUMO

The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) - RNA-guided Cas9 endonuclease system has provided a fast and efficient method for precise genome editing in diverse mammalian species, including humans. The CRISPR/Cas9 technology allows generation of modifications into site-specific locations of the selected genes in one major step by carrying deletions, insertions or DNA donor-directed precise sequence modifications. Cas9 forms a nucleoprotein complex with a sequence-specific guide RNA to create double-stranded breaks in complementary DNA target. Further, double-stranded break repair machinery leads to the intended gene modifications. The CRISPR/Cas9 system is widely used technique for genome modification, editing and other biotechnology applications, such as functional annotation, a system for visualization of specific genomic loci and transcriptional control of genes. CRISPR/Cas9-mediated manipulation of the laboratory animal genomes has contributed to the understanding of gene functions and has become a popular approach for modeling human disorders. Furthermore, the growing application of CRISPR-Cas9 system to human genes emerges as an extremely powerful technology for the molecular characterization and treatment of human disease. In this review we present the essential principles of CRISPR/Cas9 technology and the recent advances in its use in translational biomedicine.


Assuntos
Sistemas CRISPR-Cas/genética , Edição de Genes/métodos , Regulação da Expressão Gênica/genética , Terapia Genética/métodos , Animais , Sistemas CRISPR-Cas/fisiologia , Caspase 9/química , Caspase 9/genética , Caspase 9/metabolismo , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas/genética , Quebras de DNA de Cadeia Dupla , Reparo do DNA por Junção de Extremidades/genética , Modelos Animais de Doenças , Engenharia Genética/métodos , Recombinação Homóloga/genética , Humanos , RNA Guia/genética
16.
Nat Commun ; 11(1): 2055, 2020 04 28.
Artigo em Inglês | MEDLINE | ID: mdl-32345962

RESUMO

Breast cancer susceptibility gene II (BRCA2) is central in homologous recombination (HR). In meiosis, BRCA2 binds to MEILB2 to localize to DNA double-strand breaks (DSBs). Here, we identify BRCA2 and MEILB2-associating protein 1 (BRME1), which functions as a stabilizer of MEILB2 by binding to an α-helical N-terminus of MEILB2 and preventing MEILB2 self-association. BRCA2 binds to the C-terminus of MEILB2, resulting in the formation of the BRCA2-MEILB2-BRME1 ternary complex. In Brme1 knockout (Brme1-/-) mice, the BRCA2-MEILB2 complex is destabilized, leading to defects in DSB repair, homolog synapsis, and crossover formation. Persistent DSBs in Brme1-/- reactivate the somatic-like DNA-damage response, which repairs DSBs but cannot complement the crossover formation defects. Further, MEILB2-BRME1 is activated in many human cancers, and somatically expressed MEILB2-BRME1 impairs mitotic HR. Thus, the meiotic BRCA2 complex is central in meiotic HR, and its misregulation is implicated in cancer development.


Assuntos
Proteína BRCA2/metabolismo , Recombinação Homóloga/genética , Meiose/genética , Mitose/genética , Complexos Multiproteicos/metabolismo , Neoplasias/genética , Rad51 Recombinase/metabolismo , Alelos , Animais , Linhagem Celular Tumoral , Pareamento Cromossômico , Quebras de DNA de Cadeia Dupla , Masculino , Camundongos Endogâmicos C57BL , Ligação Proteica , Estabilidade Proteica , Espermatozoides/metabolismo
17.
PLoS One ; 15(3): e0230126, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32226034

RESUMO

The generation of genetically modified mouse models derived from gene targeting (GT) in mouse embryonic stem (ES) cells (mESCs) has greatly advanced both basic and clinical research. Our previous finding that gene targeting at the Myh9 exon2 site in mESCs has a pronounced high homologous recombination (HR) efficiency (>90%) has facilitated the generation of a series of nonmuscle myosin II (NM II) related mouse models. Furthermore, the Myh9 gene locus has been well demonstrated to be a new safe harbor for site-specific insertion of other exogenous genes. In the current study, we intend to investigate the molecular biology underlying for this high HR efficiency from other aspects. Our results confirmed some previously characterized properties and revealed some unreported observations: 1) The comparison and analysis of the targeting events occurring at the Myh9 and several widely used loci for targeting transgenesis, including ColA1, HPRT, ROSA26, and the sequences utilized for generating these targeting constructs, indicated that a total length about 6 kb with approximate 50% GC-content of the 5' and 3' homologous arms, may facilitate a better performance in terms of GT efficiency. 2) Despite increasing the length of the homologous arms, shifting the targeting site from the Myh9 exon2, to intron2, or exon3 led to a gradually reduced GT frequency (91.7, 71.8 and 50.0%, respectively). This finding provides the first evidence that the HR frequency may also be associated with the targeting site even in the same locus. Meanwhile, the decreased trend of the GT efficiency at these targeting sites was consistent with the reduced percentage of simple sequence repeat (SSR) and short interspersed nuclear elements (SINEs) in the sequences for generating the targeting constructs, suggesting the potential effects of these DNA elements on GT efficiency; 3) Our series of targeting experiments and analyses with truncated 5' and 3' arms at the Myh9 exon2 site demonstrated that GT efficiency positively correlates with the total length of the homologous arms (R = 0.7256, p<0.01), confirmed that a 2:1 ratio of the length, a 50% GC-content and the higher amount of SINEs for the 5' and 3' arms may benefit for appreciable GT frequency. Though more investigations are required, the Myh9 gene locus appears to be an ideal location for identifying HR-related cis and trans factors, which in turn provide mechanistic insights and also facilitate the practical application of gene editing.


Assuntos
Marcação de Genes , Recombinação Homóloga/genética , Cadeias Pesadas de Miosina/genética , Animais , Edição de Genes/métodos , Marcação de Genes/métodos , Técnicas de Genotipagem , Camundongos , Camundongos Transgênicos , Células-Tronco Embrionárias Murinas , Transformação Genética
18.
PLoS Genet ; 16(3): e1008620, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32134928

RESUMO

Candida glabrata, a nosocomial fungal bloodstream pathogen, causes significant morbidity and mortality in hospitals worldwide. The ability to replicate in macrophages and survive a high level of oxidative stress contributes to its virulence in the mammalian host. However, the role of DNA repair and recombination mechanisms in its pathobiology is still being discovered. Here, we have characterized the response of C. glabrata to the methyl methanesulfonate (MMS)-induced DNA damage. We found that the MMS exposure triggered a significant downregulation of histone H4 transcript and protein levels, and that, the damaged DNA was repaired by the homologous recombination (HR) pathway. Consistently, the reduced H4 gene dosage was associated with increased HR frequency and elevated resistance to MMS. The genetic analysis found CgRad52, a DNA strand exchange-promoter protein of the HR system, to be essential for this MMS resistance. Further, the tandem-affinity purification and mass spectrometry analysis revealed a substantially smaller interactome of H4 in MMS-treated cells. Among 23 identified proteins, we found the WD40-repeat protein CgCmr1 to interact genetically and physically with H4, and regulate H4 levels, HR pathway and MMS stress survival. Controlling H4 levels tightly is therefore a regulatory mechanism to survive MMS stress in C. glabrata.


Assuntos
Candida glabrata/genética , Dano ao DNA/genética , Histonas/genética , Recombinação Homóloga/genética , DNA/genética , Reparo do DNA/genética , Proteínas de Ligação a DNA/genética , Metanossulfonato de Metila/metabolismo
19.
J Biosci ; 452020.
Artigo em Inglês | MEDLINE | ID: mdl-32020912

RESUMO

In order to improve crop plants in terms of their yield, drought resistance, pest resistance, nutritional value, etc., modern agriculture has relied upon plant genetic engineering. Since the advent of recombinant DNA technology, several tools have been used for genetic transformations in plants such as Agrobacterium tumefaciens, virus-mediated gene transfer, direct gene transfer systems such as electroporation, particle gun, microinjection and chemical methods. All these traditional methods lack specificity and the transgenes are integrated at random sites in the plant DNA. Recently novel techniques for gene targeting have evolved such as engineered nucleases such as Zinc Finger Nucleases, Transcription Activator like effector nucleases, Clustered regular interspaced short palindromic repeats. Other advances include improvement in tools for delivery of gene editing components which include carrier proteins, and carbon nanotubes. The present review focuses on the latest techniques for target specific gene delivery in plants, their expression and future directions in plant biotechnology.


Assuntos
Sistemas CRISPR-Cas/genética , Edição de Genes/métodos , Engenharia Genética/métodos , Recombinação Homóloga/genética , Plantas/genética , Plantas/microbiologia , Nucleases dos Efetores Semelhantes a Ativadores de Transcrição/genética , Nucleases de Dedos de Zinco/genética , Endonucleases , Marcação de Genes , Terapia Genética , Nanotubos de Carbono
20.
Genes Dev ; 34(5-6): 398-412, 2020 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-32001511

RESUMO

Chromatin barriers prevent spurious interactions between regulatory elements and DNA-binding proteins. One such barrier, whose mechanism for overcoming is poorly understood, is access to recombination hot spots during meiosis. Here we show that the chromatin remodeler HELLS and DNA-binding protein PRDM9 function together to open chromatin at hot spots and provide access for the DNA double-strand break (DSB) machinery. Recombination hot spots are decorated by a unique combination of histone modifications not found at other regulatory elements. HELLS is recruited to hot spots by PRDM9 and is necessary for both histone modifications and DNA accessibility at hot spots. In male mice lacking HELLS, DSBs are retargeted to other sites of open chromatin, leading to germ cell death and sterility. Together, these data provide a model for hot spot activation in which HELLS and PRDM9 form a pioneer complex to create a unique epigenomic environment of open chromatin, permitting correct placement and repair of DSBs.


Assuntos
DNA Helicases/metabolismo , Histona-Lisina N-Metiltransferase/metabolismo , Recombinação Homóloga/genética , Meiose/fisiologia , Animais , Morte Celular/genética , Quebras de DNA de Cadeia Dupla , Células Germinativas/patologia , Código das Histonas/genética , Infertilidade Masculina/genética , Infertilidade Masculina/fisiopatologia , Substâncias Macromoleculares/metabolismo , Masculino , Meiose/genética , Camundongos
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