Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 266
Filtrar
1.
PLoS Genet ; 16(12): e1008603, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33370275

RESUMO

Telomeres have the ability to adopt a lariat conformation and hence, engage in long and short distance intra-chromosome interactions. Budding yeast telomeres were proposed to fold back into subtelomeric regions, but a robust assay to quantitatively characterize this structure has been lacking. Therefore, it is not well understood how the interactions between telomeres and non-telomeric regions are established and regulated. We employ a telomere chromosome conformation capture (Telo-3C) approach to directly analyze telomere folding and its maintenance in S. cerevisiae. We identify the histone modifiers Sir2, Sin3 and Set2 as critical regulators for telomere folding, which suggests that a distinct telomeric chromatin environment is a major requirement for the folding of yeast telomeres. We demonstrate that telomeres are not folded when cells enter replicative senescence, which occurs independently of short telomere length. Indeed, Sir2, Sin3 and Set2 protein levels are decreased during senescence and their absence may thereby prevent telomere folding. Additionally, we show that the homologous recombination machinery, including the Rad51 and Rad52 proteins, as well as the checkpoint component Rad53 are essential for establishing the telomere fold-back structure. This study outlines a method to interrogate telomere-subtelomere interactions at a single unmodified yeast telomere. Using this method, we provide insights into how the spatial arrangement of the chromosome end structure is established and demonstrate that telomere folding is compromised throughout replicative senescence.


Assuntos
Replicação do DNA , Histona Desacetilases/metabolismo , Metiltransferases/metabolismo , Proteínas Repressoras/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas Reguladoras de Informação Silenciosa de Saccharomyces cerevisiae/metabolismo , Sirtuína 2/metabolismo , Telômero/genética , Histona Desacetilases/genética , Metiltransferases/genética , Rad51 Recombinase/genética , Rad51 Recombinase/metabolismo , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Proteína Rad52 de Recombinação e Reparo de DNA/metabolismo , Proteínas Repressoras/genética , Saccharomyces cerevisiae , Proteínas de Saccharomyces cerevisiae/genética , Proteínas Reguladoras de Informação Silenciosa de Saccharomyces cerevisiae/genética , Sirtuína 2/genética , Telômero/química , Homeostase do Telômero
2.
Mol Cell ; 79(6): 1037-1050.e5, 2020 09 17.
Artigo em Inglês | MEDLINE | ID: mdl-32882183

RESUMO

DNA double-stranded breaks (DSBs) are dangerous lesions threatening genomic stability. Fidelity of DSB repair is best achieved by recombination with a homologous template sequence. In yeast, transcript RNA was shown to template DSB repair of DNA. However, molecular pathways of RNA-driven repair processes remain obscure. Utilizing assays of RNA-DNA recombination with and without an induced DSB in yeast DNA, we characterize three forms of RNA-mediated genomic modifications: RNA- and cDNA-templated DSB repair (R-TDR and c-TDR) using an RNA transcript or a DNA copy of the RNA transcript for DSB repair, respectively, and a new mechanism of RNA-templated DNA modification (R-TDM) induced by spontaneous or mutagen-induced breaks. While c-TDR requires reverse transcriptase, translesion DNA polymerase ζ (Pol ζ) plays a major role in R-TDR, and it is essential for R-TDM. This study characterizes mechanisms of RNA-DNA recombination, uncovering a role of Pol ζ in transferring genetic information from transcript RNA to DNA.


Assuntos
DNA/genética , RNA/genética , Saccharomyces cerevisiae/genética , Adolescente , Adulto , DNA/ultraestrutura , Quebras de DNA de Cadeia Dupla , Reparo do DNA/genética , Replicação do DNA/genética , DNA Complementar/genética , DNA Polimerase Dirigida por DNA/genética , DNA Polimerase Dirigida por DNA/ultraestrutura , Instabilidade Genômica/genética , Humanos , Pessoa de Meia-Idade , RNA/ultraestrutura , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Adulto Jovem
3.
Proc Natl Acad Sci U S A ; 117(28): 16527-16536, 2020 07 14.
Artigo em Inglês | MEDLINE | ID: mdl-32601218

RESUMO

Folate deprivation drives the instability of a group of rare fragile sites (RFSs) characterized by CGG trinucleotide repeat (TNR) sequences. Pathological expansion of the TNR within the FRAXA locus perturbs DNA replication and is the major causative factor for fragile X syndrome, a sex-linked disorder associated with cognitive impairment. Although folate-sensitive RFSs share many features with common fragile sites (CFSs; which are found in all individuals), they are induced by different stresses and share no sequence similarity. It is known that a pathway (termed MiDAS) is employed to complete the replication of CFSs in early mitosis. This process requires RAD52 and is implicated in generating translocations and copy number changes at CFSs in cancers. However, it is unclear whether RFSs also utilize MiDAS and to what extent the fragility of CFSs and RFSs arises by shared or distinct mechanisms. Here, we demonstrate that MiDAS does occur at FRAXA following folate deprivation but proceeds via a pathway that shows some mechanistic differences from that at CFSs, being dependent on RAD51, SLX1, and POLD3. A failure to complete MiDAS at FRAXA leads to severe locus instability and missegregation in mitosis. We propose that break-induced DNA replication is required for the replication of FRAXA under folate stress and define a cellular function for human SLX1. These findings provide insights into how folate deprivation drives instability in the human genome.


Assuntos
Endodesoxirribonucleases/metabolismo , Ácido Fólico/metabolismo , Síndrome do Cromossomo X Frágil/metabolismo , Mitose , Rad51 Recombinase/metabolismo , DNA/genética , DNA/metabolismo , Reparo do DNA , Endodesoxirribonucleases/genética , Síndrome do Cromossomo X Frágil/genética , Síndrome do Cromossomo X Frágil/fisiopatologia , Humanos , Rad51 Recombinase/genética , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Proteína Rad52 de Recombinação e Reparo de DNA/metabolismo , Recombinases/genética , Recombinases/metabolismo
4.
PLoS Genet ; 16(7): e1008924, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32673314

RESUMO

Microsatellites are short tandem repeats, ubiquitous in all eukaryotes and represent ~2% of the human genome. Among them, trinucleotide repeats are responsible for more than two dozen neurological and developmental disorders. Targeting microsatellites with dedicated DNA endonucleases could become a viable option for patients affected with dramatic neurodegenerative disorders. Here, we used the Streptococcus pyogenes Cas9 to induce a double-strand break within the expanded CTG repeat involved in myotonic dystrophy type 1, integrated in a yeast chromosome. Repair of this double-strand break generated unexpected large chromosomal deletions around the repeat tract. These deletions depended on RAD50, RAD52, DNL4 and SAE2, and both non-homologous end-joining and single-strand annealing pathways were involved. Resection and repair of the double-strand break (DSB) were totally abolished in a rad50Δ strain, whereas they were impaired in a sae2Δ mutant, only on the DSB end containing most of the repeat tract. This observation demonstrates that Sae2 plays significant different roles in resecting a DSB end containing a repeated and structured sequence as compared to a non-repeated DSB end. In addition, we also discovered that gene conversion was less efficient when the DSB could be repaired using a homologous template, suggesting that the trinucleotide repeat may interfere with gene conversion too. Altogether, these data show that SpCas9 may not be the best choice when inducing a double-strand break at or near a microsatellite, especially in mammalian genomes that contain many more dispersed repeated elements than the yeast genome.


Assuntos
Quebras de DNA de Cadeia Dupla , Distrofia Miotônica/genética , Recombinação Genética , Repetições de Trinucleotídeos/genética , Proteína 9 Associada à CRISPR/genética , Sistemas CRISPR-Cas , Deleção Cromossômica , Cromossomos Fúngicos/genética , Reparo do DNA por Junção de Extremidades/genética , DNA Ligase Dependente de ATP/genética , Reparo do DNA/genética , Proteínas de Ligação a DNA/genética , Endonucleases/genética , Conversão Gênica/genética , Genoma Humano/genética , Humanos , Distrofia Miotônica/patologia , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Expansão das Repetições de Trinucleotídeos/genética
5.
Nat Struct Mol Biol ; 27(5): 424-437, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32398827

RESUMO

Oncogene activation during tumorigenesis generates DNA replication stress, a known driver of genome rearrangements. In response to replication stress, certain loci, such as common fragile sites and telomeres, remain under-replicated during interphase and subsequently complete locus duplication in mitosis in a process known as 'MiDAS'. Here, we demonstrate that RTEL1 (regulator of telomere elongation helicase 1) has a genome-wide role in MiDAS at loci prone to form G-quadruplex-associated R-loops, in a process that is dependent on its helicase function. We reveal that SLX4 is required for the timely recruitment of RTEL1 to the affected loci, which in turn facilitates recruitment of other proteins required for MiDAS, including RAD52 and POLD3. Our findings demonstrate that RTEL1 is required for MiDAS and suggest that RTEL1 maintains genome stability by resolving conflicts that can arise between the replication and transcription machineries.


Assuntos
DNA Helicases/genética , DNA Helicases/metabolismo , Quadruplex G , Genoma Humano/genética , Mitose , Animais , Linhagem Celular , DNA Helicases/química , DNA Polimerase III/genética , DNA Polimerase III/metabolismo , Instabilidade Genômica , Humanos , Imunoprecipitação , Camundongos , Enzimas Multifuncionais/genética , Enzimas Multifuncionais/metabolismo , Conformação de Ácido Nucleico , RNA Helicases/genética , RNA Helicases/metabolismo , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Proteína Rad52 de Recombinação e Reparo de DNA/metabolismo , Recombinases/genética , Recombinases/metabolismo , Ribonuclease H/genética , Ribonuclease H/metabolismo
6.
PLoS Genet ; 16(2): e1008608, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-32012161

RESUMO

DNA double-strand breaks (DSBs) are toxic forms of DNA damage that must be repaired to maintain genome integrity. Telomerase can act upon a DSB to create a de novo telomere, a process that interferes with normal repair and creates terminal deletions. We previously identified sequences in Saccharomyces cerevisiae (SiRTAs; Sites of Repair-associated Telomere Addition) that undergo unusually high frequencies of de novo telomere addition, even when the original chromosome break is several kilobases distal to the eventual site of telomerase action. Association of the single-stranded telomere binding protein Cdc13 with a SiRTA is required to stimulate de novo telomere addition. Because extensive resection must occur prior to Cdc13 binding, we utilized these sites to monitor the effect of proteins involved in homologous recombination. We find that telomere addition is significantly reduced in the absence of the Rad51 recombinase, while loss of Rad52, required for Rad51 nucleoprotein filament formation, has no effect. Deletion of RAD52 suppresses the defect of the rad51Δ strain, suggesting that Rad52 inhibits de novo telomere addition in the absence of Rad51. The ability of Rad51 to counteract this effect of Rad52 does not require DNA binding by Rad51, but does require interaction between the two proteins, while the inhibitory effect of Rad52 depends on its interaction with Replication Protein A (RPA). Intriguingly, the genetic interactions we report between RAD51 and RAD52 are similar to those previously observed in the context of checkpoint adaptation. Forced recruitment of Cdc13 fully restores telomere addition in the absence of Rad51, suggesting that Rad52, through its interaction with RPA-coated single-stranded DNA, inhibits the ability of Cdc13 to bind and stimulate telomere addition. Loss of the Rad51-Rad52 interaction also stimulates a subset of Rad52-dependent microhomology-mediated repair (MHMR) events, consistent with the known ability of Rad51 to prevent single-strand annealing.


Assuntos
Rad51 Recombinase/metabolismo , Proteína Rad52 de Recombinação e Reparo de DNA/metabolismo , Reparo de DNA por Recombinação , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/genética , Telômero/metabolismo , Quebras de DNA de Cadeia Dupla , Técnicas de Inativação de Genes , Mutação , Ligação Proteica/genética , Rad51 Recombinase/genética , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Telomerase/metabolismo , Proteínas de Ligação a Telômeros/metabolismo
7.
Nat Commun ; 11(1): 695, 2020 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-32019927

RESUMO

Cellular processes are influenced by liquid phase separation, but its role in DNA repair is unclear. Here, we show that in Saccharomyces cerevisiae, liquid droplets made up of DNA repair proteins cooperate with different types of DNA damage-inducible intranuclear microtubule filaments (DIMs) to promote the clustering of DNA damage sites and maintain genome stability. Rad52 DNA repair proteins at different DNA damage sites assemble in liquid droplets that fuse into a repair centre droplet via the action of petite DIMs (pti-DIMs). This larger droplet concentrates tubulin and projects short aster-like DIMs (aster-DIMs), which tether the repair centre to longer DIMs mediating the mobilization of damaged DNA to the nuclear periphery for repair. Our findings indicate that cooperation between Rad52 liquid droplets and various types of nuclear filaments promotes the assembly and function of the DNA repair centre.


Assuntos
Reparo do DNA , Proteína Rad52 de Recombinação e Reparo de DNA/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Núcleo Celular/genética , Núcleo Celular/metabolismo , Dano ao DNA , DNA Fúngico/genética , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Tubulina (Proteína)/genética , Tubulina (Proteína)/metabolismo
8.
Biochem Biophys Res Commun ; 522(1): 121-126, 2020 01 29.
Artigo em Inglês | MEDLINE | ID: mdl-31753490

RESUMO

Lung cancer is the leading cause of cancer death worldwide. PARP inhibitors have become a new line of cancer therapy and a successful demonstration of the synthetic lethality concept. The mechanism and efficacy of PARP inhibitors have been well studied in some cancers, especially homologous recombination (HR)-deficient ovarian cancer and breast cancer, yet such studies are still relatively fewer in lung cancer. Here we found that HR genes are frequently mutated in lung cancer patients, exposing a window for targeted therapies by PARP inhibitors. We depleted BRCA1 and BRCA2 in non-small cell lung cancer (NSCLC) cancer cells and found these cells are hypersensitive to the PARP inhibitor olaparib in cell viability and clonogenic survival assays. Olaparib specifically induces apoptosis in A549 cells with BRCA1 or BRCA2 depletion, as determined by positive Annexin-V staining. In addition, we show that A549 cells with ATM shRNA knockdown are also hypersensitive to Olaparib. In summary, our data support the potential use of PARP inhibitors in NSCLC with HR deficiency.


Assuntos
Carcinoma Pulmonar de Células não Pequenas/genética , Neoplasias Pulmonares/genética , Inibidores de Poli(ADP-Ribose) Polimerases/farmacologia , Células A549 , Proteínas Mutadas de Ataxia Telangiectasia/genética , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Proteína BRCA1/genética , Proteína BRCA2/genética , Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Linhagem Celular Tumoral , Sobrevivência Celular , Recombinação Homóloga/efeitos dos fármacos , Humanos , Neoplasias Pulmonares/tratamento farmacológico , Proteína Homóloga a MRE11/genética , Mutação , Ftalazinas/farmacologia , Piperazinas/farmacologia , Rad51 Recombinase/genética , Proteína Rad52 de Recombinação e Reparo de DNA/genética
9.
Nucleic Acids Res ; 48(3): 1285-1300, 2020 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-31777915

RESUMO

Reactive oxygen species (ROS) inflict multiple types of lesions in DNA, threatening genomic integrity. How cells respond to ROS-induced DNA damage at telomeres is still largely unknown. Here, we show that ROS-induced DNA damage at telomeres triggers R-loop accumulation in a TERRA- and TRF2-dependent manner. Both ROS-induced single- and double-strand DNA breaks (SSBs and DSBs) contribute to R-loop induction, promoting the localization of CSB and RAD52 to damaged telomeres. RAD52 is recruited to telomeric R-loops through its interactions with both CSB and DNA:RNA hybrids. Both CSB and RAD52 are required for the efficient repair of ROS-induced telomeric DSBs. The function of RAD52 in telomere repair is dependent on its ability to bind and recruit POLD3, a protein critical for break-induced DNA replication (BIR). Thus, ROS-induced telomeric R-loops promote repair of telomeric DSBs through CSB-RAD52-POLD3-mediated BIR, a previously unknown pathway protecting telomeres from ROS. ROS-induced telomeric SSBs may not only give rise to DSBs indirectly, but also promote DSB repair by inducing R-loops, revealing an unexpected interplay between distinct ROS-induced DNA lesions.


Assuntos
DNA Helicases/genética , DNA Polimerase III/genética , Enzimas Reparadoras do DNA/genética , Proteínas de Ligação a Poli-ADP-Ribose/genética , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Telômero/genética , Quebras de DNA de Cadeia Dupla , Quebras de DNA de Cadeia Simples , Reparo do DNA/genética , Replicação do DNA/genética , Proteínas de Ligação a DNA/genética , Células HeLa , Humanos , Estruturas R-Loop , Espécies Reativas de Oxigênio/metabolismo , Proteína 2 de Ligação a Repetições Teloméricas/genética , Fatores de Transcrição/genética
10.
Nucleic Acids Res ; 48(2): 694-708, 2020 01 24.
Artigo em Inglês | MEDLINE | ID: mdl-31799622

RESUMO

The proper repair of deleterious DNA lesions such as double strand breaks prevents genomic instability and carcinogenesis. In yeast, the Rad52 protein mediates DSB repair via homologous recombination. In mammalian cells, despite the presence of the RAD52 protein, the tumour suppressor protein BRCA2 acts as the predominant mediator during homologous recombination. For decades, it has been believed that the RAD52 protein played only a back-up role in the repair of DSBs performing an error-prone single strand annealing (SSA). Recent studies have identified several new functions of the RAD52 protein and have drawn attention to its important role in genome maintenance. Here, we show that RAD52 activities are enhanced by interacting with a small and highly acidic protein called DSS1. Binding of DSS1 to RAD52 changes the RAD52 oligomeric conformation, modulates its DNA binding properties, stimulates SSA activity and promotes strand invasion. Our work introduces for the first time RAD52 as another interacting partner of DSS1 and shows that both proteins are important players in the SSA and BIR pathways of DSB repair.


Assuntos
Carcinogênese/genética , Recombinação Homóloga/genética , Complexo de Endopeptidases do Proteassoma/genética , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Proteína BRCA2/genética , Quebras de DNA de Cadeia Dupla , Reparo do DNA/genética , Proteínas de Ligação a DNA/genética , Genoma Humano/genética , Instabilidade Genômica/genética , Humanos , Osteossarcoma/genética , Osteossarcoma/patologia , Ligação Proteica , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética
11.
Nucleic Acids Res ; 48(4): 1905-1924, 2020 02 28.
Artigo em Inglês | MEDLINE | ID: mdl-31832684

RESUMO

In vertebrates, genomic DNA double-strand breaks (DSBs) are removed by non-homologous end-joining processes: classical non-homologous end-joining (c-NHEJ) and alternative end-joining (alt-EJ); or by homology-dependent processes: gene-conversion (GC) and single-strand annealing (SSA). Surprisingly, these repair pathways are not real alternative options restoring genome integrity with equal efficiency, but show instead striking differences in speed, accuracy and cell-cycle-phase dependence. As a consequence, engagement of one pathway may be associated with processing-risks for the genome absent from another pathway. Characterization of engagement-parameters and their consequences is, therefore, essential for understanding effects on the genome of DSB-inducing agents, such as ionizing-radiation (IR). Here, by addressing pathway selection in G2-phase, we discover regulatory confinements in GC with consequences for SSA- and c-NHEJ-engagement. We show pronounced suppression of GC with increasing DSB-load that is not due to RAD51 availability and which is delimited but not defined by 53BP1 and RAD52. Strikingly, at low DSB-loads, GC repairs ∼50% of DSBs, whereas at high DSB-loads its contribution is undetectable. Notably, with increasing DSB-load and the associated suppression of GC, SSA gains ground, while alt-EJ is suppressed. These observations explain earlier, apparently contradictory results and advance our understanding of logic and mechanisms underpinning the wiring between DSB repair pathways.


Assuntos
Conversão Gênica/genética , Rad51 Recombinase/genética , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética , Células A549 , Animais , Quebras de DNA de Cadeia Dupla/efeitos da radiação , Reparo do DNA por Junção de Extremidades/genética , Reparo do DNA/genética , Regulação da Expressão Gênica/efeitos da radiação , Humanos , Radiação Ionizante
12.
Aging Cell ; 19(2): e13068, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31833215

RESUMO

Maf1 is the master repressor of RNA polymerase III responsible for transcription of tRNAs and 5S rRNAs. Maf1 is negatively regulated via phosphorylation by the mTOR pathway, which governs protein synthesis, growth control, and lifespan regulation in response to nutrient availability. Inhibiting the mTOR pathway extends lifespan in various organisms. However, the downstream effectors for the regulation of cell homeostasis that are critical to lifespan extension remain elusive. Here we show that fission yeast Maf1 is required for lifespan extension. Maf1's function in tRNA repression is inhibited by mTOR-dependent phosphorylation, whereas Maf1 is activated via dephosphorylation by protein phosphatase complexes, PP4 and PP2A. Mutational analysis reveals that Maf1 phosphorylation status influences lifespan, which is correlated with elevated tRNA and protein synthesis levels in maf1∆ cells. However, mTOR downregulation, which negates protein synthesis, fails to rescue the short lifespan of maf1∆ cells, suggesting that elevated protein synthesis is not a cause of lifespan shortening in maf1∆ cells. Interestingly, maf1∆ cells accumulate DNA damage represented by formation of Rad52 DNA damage foci and Rad52 recruitment at tRNA genes. Loss of the Rad52 DNA repair protein further exacerbates the shortened lifespan of maf1∆ cells. Strikingly, PP4 deletion alleviates DNA damage and rescues the short lifespan of maf1∆ cells even though tRNA synthesis is increased in this condition, suggesting that elevated DNA damage is the major cause of lifespan shortening in maf1∆ cells. We propose that Maf1-dependent inhibition of tRNA synthesis controls fission yeast lifespan by preventing genomic instability that arises at tRNA genes.


Assuntos
Regulação Fúngica da Expressão Gênica , Instabilidade Genômica/genética , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , RNA de Transferência/genética , Proteínas Repressoras/metabolismo , Proteínas de Schizosaccharomyces pombe/metabolismo , Schizosaccharomyces/genética , Imunoprecipitação da Cromatina , Dano ao DNA/genética , Glucose/metabolismo , Alvo Mecanístico do Complexo 1 de Rapamicina/genética , Fosfoproteínas Fosfatases/genética , Fosfoproteínas Fosfatases/metabolismo , Fosforilação , Biossíntese de Proteínas/genética , Biossíntese de Proteínas/fisiologia , Proteína Fosfatase 2/genética , Proteína Fosfatase 2/metabolismo , RNA de Transferência/biossíntese , RNA de Transferência/metabolismo , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Proteína Rad52 de Recombinação e Reparo de DNA/metabolismo , Proteínas Repressoras/genética , Schizosaccharomyces/metabolismo , Schizosaccharomyces/fisiologia , Proteínas de Schizosaccharomyces pombe/genética
13.
Genetics ; 213(3): 819-834, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31533921

RESUMO

The accuracy of most DNA processes depends on chromatin integrity and dynamics. Our analyses in the yeast Saccharomyces cerevisiae show that an absence of Swr1 (the catalytic and scaffold subunit of the chromatin-remodeling complex SWR) leads to the formation of long-duration Rad52, but not RPA, foci and to an increase in intramolecular recombination. These phenotypes are further increased by MMS, zeocin, and ionizing radiation, but not by double-strand breaks, HU, or transcription/replication collisions, suggesting that they are associated with specific DNA lesions. Importantly, these phenotypes can be specifically suppressed by mutations in: (1) chromatin-anchorage internal nuclear membrane components (mps3∆75-150 and src1∆); (2) actin and actin regulators (act1 -157, act1 -159, crn1∆, and cdc42 -6); or (3) the SWR subunit Swc5 and the SWR substrate Htz1 However, they are not suppressed by global disruption of actin filaments or by the absence of Csm4 (a component of the external nuclear membrane that forms a bridging complex with Mps3, thus connecting the actin cytoskeleton with chromatin). Moreover, swr1∆-induced Rad52 foci and intramolecular recombination are not associated with tethering recombinogenic DNA lesions to the nuclear periphery. In conclusion, the absence of Swr1 impairs efficient recombinational repair of specific DNA lesions by mechanisms that are influenced by SWR subunits, including actin, and nuclear envelope components. We suggest that these recombinational phenotypes might be associated with a pathological effect on homologous recombination of actin-containing complexes.


Assuntos
Citoesqueleto de Actina/metabolismo , Adenosina Trifosfatases/genética , Recombinação Homóloga , Membrana Nuclear/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Citoesqueleto de Actina/genética , Actinas/genética , Actinas/metabolismo , Adenosina Trifosfatases/deficiência , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Membrana Nuclear/genética , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Proteína Rad52 de Recombinação e Reparo de DNA/metabolismo , Saccharomyces cerevisiae , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteína cdc42 de Saccharomyces cerevisiae de Ligação ao GTP/genética , Proteína cdc42 de Saccharomyces cerevisiae de Ligação ao GTP/metabolismo
14.
Mol Cell ; 76(5): 699-711.e6, 2019 12 05.
Artigo em Inglês | MEDLINE | ID: mdl-31542296

RESUMO

Rad52 is a key factor for homologous recombination (HR) in yeast. Rad52 helps assemble Rad51-ssDNA nucleoprotein filaments that catalyze DNA strand exchange, and it mediates single-strand DNA annealing. We find that Rad52 has an even earlier function in HR in restricting DNA double-stranded break ends resection that generates 3' single-stranded DNA (ssDNA) tails. In fission yeast, Exo1 is the primary resection nuclease, with the helicase Rqh1 playing a minor role. We demonstrate that the choice of two extensive resection pathways is regulated by Rad52. In rad52 cells, the resection rate increases from ∼3-5 kb/h up to ∼10-20 kb/h in an Rqh1-dependent manner, while Exo1 becomes dispensable. Budding yeast Rad52 similarly inhibits Sgs1-dependent resection. Single-molecule analysis with purified budding yeast proteins shows that Rad52 competes with Sgs1 for DNA end binding and inhibits Sgs1 translocation along DNA. These results identify a role for Rad52 in limiting ssDNA generated by end resection.


Assuntos
Quebras de DNA de Cadeia Dupla , Quebras de DNA de Cadeia Simples , Reparo do DNA , DNA Fúngico/metabolismo , Proteínas de Ligação a DNA/metabolismo , Proteína Rad52 de Recombinação e Reparo de DNA/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/enzimologia , Proteínas de Schizosaccharomyces pombe/metabolismo , Schizosaccharomyces/enzimologia , DNA Helicases/genética , DNA Helicases/metabolismo , DNA Fúngico/genética , Proteínas de Ligação a DNA/genética , Exodesoxirribonucleases/genética , Exodesoxirribonucleases/metabolismo , Regulação Fúngica da Expressão Gênica , Cinética , Mutação , Domínios Proteicos , Transporte Proteico , Proteína Rad52 de Recombinação e Reparo de DNA/genética , RecQ Helicases/genética , RecQ Helicases/metabolismo , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Schizosaccharomyces/genética , Proteínas de Schizosaccharomyces pombe/genética
15.
Cancer Res ; 79(21): 5597-5611, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31515237

RESUMO

Head and neck squamous cell carcinoma (HNSCC) is characterized by the frequent manifestation of DNA crosslink repair defects. We established novel expression-based DNA repair defect markers to determine the clinical impact of such repair defects. Using hypersensitivity to the DNA crosslinking agents, mitomycin C and olaparib, as proxies for functional DNA repair defects in a panel of 25 HNSCC cell lines, we applied machine learning to define gene expression models that predict repair defects. The expression profiles established predicted hypersensitivity to DNA-damaging agents and were associated with mutations in crosslink repair genes, as well as downregulation of DNA damage response and repair genes, in two independent datasets. The prognostic value of the repair defect prediction profiles was assessed in two retrospective cohorts with a total of 180 patients with advanced HPV-negative HNSCC, who were treated with cisplatin-based chemoradiotherapy. DNA repair defects, as predicted by the profiles, were associated with poor outcome in both patient cohorts. The poor prognosis association was particularly strong in normoxic tumor samples and was linked to an increased risk of distant metastasis. In vitro, only crosslink repair-defective HNSCC cell lines are highly migratory and invasive. This phenotype could also be induced in cells by inhibiting rad51 in repair competent and reduced by DNA-PK inhibition. In conclusion, DNA crosslink repair prediction expression profiles reveal a poor prognosis association in HNSCC. SIGNIFICANCE: This study uses innovative machine learning-based approaches to derive models that predict the effect of DNA repair defects on treatment outcome in HNSCC.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/21/5597/F1.large.jpg.


Assuntos
Antineoplásicos/farmacologia , Reparo do DNA/efeitos dos fármacos , Neoplasias de Cabeça e Pescoço/tratamento farmacológico , Neoplasias de Cabeça e Pescoço/patologia , Carcinoma de Células Escamosas de Cabeça e Pescoço/tratamento farmacológico , Carcinoma de Células Escamosas de Cabeça e Pescoço/patologia , Apoptose/efeitos dos fármacos , Apoptose/genética , Linhagem Celular Tumoral , Quimiorradioterapia/métodos , Cisplatino/farmacologia , Dano ao DNA/efeitos dos fármacos , Dano ao DNA/genética , Reparo do DNA/genética , Expressão Gênica/efeitos dos fármacos , Expressão Gênica/genética , Neoplasias de Cabeça e Pescoço/genética , Humanos , Mutação/efeitos dos fármacos , Mutação/genética , Fenótipo , Prognóstico , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Estudos Retrospectivos , Carcinoma de Células Escamosas de Cabeça e Pescoço/genética
16.
Mol Biol Cell ; 30(21): 2620-2625, 2019 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-31483739

RESUMO

During S phase in Saccharomyces cerevisiae, chromosomal loci become mobile in response to DNA double-strand breaks both at the break site (local mobility) and throughout the nucleus (global mobility). Increased nuclear exploration is regulated by the recombination machinery and the DNA damage checkpoint and is likely an important aspect of homology search. While mobility in response to DNA damage has been studied extensively in S phase, the response in interphase has not, and the question of whether homologous recombination proceeds to completion in G1 phase remains controversial. Here, we find that global mobility is triggered in G1 phase. As in S phase, global mobility in G1 phase is controlled by the DNA damage checkpoint and the Rad51 recombinase. Interestingly, despite the restriction of Rad52 mediator foci to S phase, Rad51 foci form at high levels in G1 phase. Together, these observations indicate that the recombination and checkpoint machineries promote global mobility in G1 phase, supporting the notion that recombination can occur in interphase diploids.


Assuntos
Núcleo Celular/genética , Cromossomos Fúngicos/genética , Dano ao DNA , Fase G1/genética , Saccharomyces cerevisiae/genética , Núcleo Celular/metabolismo , Quebras de DNA de Cadeia Dupla , Reparo do DNA/genética , Recombinação Homóloga , Rad51 Recombinase/genética , Rad51 Recombinase/metabolismo , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Proteína Rad52 de Recombinação e Reparo de DNA/metabolismo , Fase S/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo
17.
PLoS Genet ; 15(8): e1008319, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31381562

RESUMO

Disrupting either the DNA annealing factor RAD52 or the A-family DNA polymerase POLQ can cause synthetic lethality with defects in BRCA1 and BRCA2, which are tumor suppressors important for homology-directed repair of DNA double-strand breaks (DSBs), and protection of stalled replication forks. A likely mechanism of this synthetic lethality is that RAD52 and/or POLQ are important for backup pathways for DSB repair and/or replication stress responses. The features of DSB repair events that require RAD52 vs. POLQ, and whether combined disruption of these factors causes distinct effects on genome maintenance, have been unclear. Using human U2OS cells, we generated a cell line with POLQ mutations upstream of the polymerase domain, a RAD52 knockout cell line, and a line with combined disruption of both genes. We also examined RAD52 and POLQ using RNA-interference. We find that combined disruption of RAD52 and POLQ causes at least additive hypersensitivity to cisplatin, and a synthetic reduction in replication fork restart velocity. We also examined the influence of RAD52 and POLQ on several DSB repair events. We find that RAD52 is particularly important for repair using ≥ 50 nt repeat sequences that flank the DSB, and that also involve removal of non-homologous sequences flanking the repeats. In contrast, POLQ is important for repair events using 6 nt (but not ≥ 18 nt) of flanking repeats that are at the edge of the break, as well as oligonucleotide microhomology-templated (i.e., 12-20 nt) repair events requiring nascent DNA synthesis. Finally, these factors show key distinctions with BRCA2, regarding effects on DSB repair events and response to stalled replication forks. These findings indicate that RAD52 and POLQ have distinct roles in genome maintenance, including for specific features of DSB repair events, such that combined disruption of these factors may be effective for genotoxin sensitization and/or synthetic lethal strategies.


Assuntos
DNA Polimerase Dirigida por DNA/genética , Resistencia a Medicamentos Antineoplásicos/genética , Neoplasias/genética , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Reparo de DNA por Recombinação , Proteína BRCA1/genética , Proteína BRCA2/genética , Linhagem Celular Tumoral , Cisplatino/farmacologia , Cisplatino/uso terapêutico , Quebras de DNA de Cadeia Dupla/efeitos dos fármacos , Replicação do DNA/efeitos dos fármacos , DNA Polimerase Dirigida por DNA/metabolismo , Humanos , Mutação , Neoplasias/tratamento farmacológico , Proteína Rad52 de Recombinação e Reparo de DNA/metabolismo , Mutações Sintéticas Letais
18.
Mol Cell ; 76(1): 11-26.e7, 2019 10 03.
Artigo em Inglês | MEDLINE | ID: mdl-31400850

RESUMO

Alternative lengthening of telomeres (ALT) is a homology-directed repair (HDR) mechanism of telomere elongation that controls proliferation in aggressive cancers. We show that the disruption of RAD51-associated protein 1 (RAD51AP1) in ALT+ cancer cells leads to generational telomere shortening. This is due to RAD51AP1's involvement in RAD51-dependent homologous recombination (HR) and RAD52-POLD3-dependent break induced DNA synthesis. RAD51AP1 KO ALT+ cells exhibit telomere dysfunction and cytosolic telomeric DNA fragments that are sensed by cGAS. Intriguingly, they activate ULK1-ATG7-dependent autophagy as a survival mechanism to mitigate DNA damage and apoptosis. Importantly, RAD51AP1 protein levels are elevated in ALT+ cells due to MMS21 associated SUMOylation. Mutation of a single SUMO-targeted lysine residue perturbs telomere dynamics. These findings indicate that RAD51AP1 is an essential mediator of the ALT mechanism and is co-opted by post-translational mechanisms to maintain telomere length and ensure proliferation of ALT+ cancer cells.


Assuntos
Proteínas de Ligação a DNA/metabolismo , Neoplasias/metabolismo , Proteínas de Ligação a RNA/metabolismo , Homeostase do Telômero , Telômero/metabolismo , Autofagia , Proteína 7 Relacionada à Autofagia/genética , Proteína 7 Relacionada à Autofagia/metabolismo , Proteína Homóloga à Proteína-1 Relacionada à Autofagia/genética , Proteína Homóloga à Proteína-1 Relacionada à Autofagia/metabolismo , Proliferação de Células , DNA Polimerase III/genética , DNA Polimerase III/metabolismo , Proteínas de Ligação a DNA/genética , Regulação Neoplásica da Expressão Gênica , Células HEK293 , Células HeLa , Recombinação Homóloga , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Ligases/genética , Ligases/metabolismo , Lisina , Neoplasias/genética , Neoplasias/patologia , Nucleotidiltransferases/genética , Nucleotidiltransferases/metabolismo , Estabilidade Proteica , Proteínas de Ligação a RNA/genética , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Proteína Rad52 de Recombinação e Reparo de DNA/metabolismo , Transdução de Sinais , Sumoilação , Telômero/genética , Telômero/patologia
19.
Mol Cancer Res ; 17(8): 1687-1698, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31113828

RESUMO

Mitotic DNA synthesis is a recently discovered mechanism that resolves late replication intermediates, thereby supporting cell proliferation under replication stress. This unusual form of DNA synthesis occurs in the absence of RAD51 or BRCA2, which led to the identification of RAD52 as a key player in this process. Notably, mitotic DNA synthesis is predominantly observed at chromosome loci that colocalize with FANCD2 foci. However, the role of this protein in mitotic DNA synthesis remains largely unknown. In this study, we investigated the role of FANCD2 and its interplay with RAD52 in mitotic DNA synthesis using aphidicolin as a universal inducer of this process. After examining eight human cell lines, we provide evidence for FANCD2 rather than RAD52 as a fundamental supporter of mitotic DNA synthesis. In cancer cell lines, FANCD2 exerts this role independently of RAD52. Surprisingly, RAD52 is dispensable for mitotic DNA synthesis in noncancerous cell lines, but these cells strongly depend on FANCD2 for this process. Therefore, RAD52 functions selectively in cancer cells as a secondary regulator in addition to FANCD2 to facilitate mitotic DNA synthesis. As an alternative to aphidicolin, we found partial inhibition of origin licensing as an effective way to induce mitotic DNA synthesis preferentially in cancer cells. Importantly, cancer cells still perform mitotic DNA synthesis by dual regulation of FANCD2 and RAD52 under such conditions. IMPLICATIONS: These key differences in mitotic DNA synthesis between cancer and noncancerous cells advance our understanding of this mechanism and can be exploited for cancer therapies.


Assuntos
DNA/biossíntese , Proteína do Grupo de Complementação D2 da Anemia de Fanconi/metabolismo , Fibroblastos/citologia , Mitose , Neoplasias/patologia , Proteína Rad52 de Recombinação e Reparo de DNA/metabolismo , Epitélio Pigmentado da Retina/citologia , Núcleo Celular , Células Cultivadas , Dano ao DNA , Reparo do DNA , Proteína do Grupo de Complementação D2 da Anemia de Fanconi/genética , Fibroblastos/metabolismo , Humanos , Neoplasias/genética , Neoplasias/metabolismo , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Epitélio Pigmentado da Retina/metabolismo
20.
Genes (Basel) ; 10(4)2019 04 08.
Artigo em Inglês | MEDLINE | ID: mdl-30965655

RESUMO

Microhomology-mediated end joining (MMEJ) anneals short, imperfect microhomologies flanking DNA breaks, producing repair products with deletions in a Ku- and RAD52-independent fashion. Puzzlingly, MMEJ preferentially selects certain microhomologies over others, even when multiple microhomologies are available. To define rules and parameters for microhomology selection, we altered the length, the position, and the level of mismatches to the microhomologies flanking homothallic switching (HO) endonuclease-induced breaks and assessed their effect on MMEJ frequency and the types of repair product formation. We found that microhomology of eight to 20 base pairs carrying no more than 20% mismatches efficiently induced MMEJ. Deletion of MSH6 did not impact MMEJ frequency. MMEJ preferentially chose a microhomology pair that was more proximal from the break. Interestingly, MMEJ events preferentially retained the centromere proximal side of the HO break, while the sequences proximal to the telomere were frequently deleted. The asymmetry in the deletional profile among MMEJ products was reduced when HO was induced on the circular chromosome. The results provide insight into how cells search and select microhomologies for MMEJ in budding yeast.


Assuntos
Quebras de DNA de Cadeia Dupla , Reparo do DNA por Junção de Extremidades/genética , Reparo do DNA/genética , Saccharomyces cerevisiae/genética , Proteínas de Ligação a DNA/genética , Endonucleases/genética , Proteína Rad52 de Recombinação e Reparo de DNA/genética , Proteínas de Saccharomyces cerevisiae/genética , Deleção de Sequência/genética
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA