Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 51
Filtrar
Filtros adicionais











País/Região como assunto
Intervalo de ano
1.
Proc Natl Acad Sci U S A ; 116(35): 17377-17382, 2019 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-31409704

RESUMO

Gross Chromosomal Rearrangements (GCRs) play an important role in human diseases, including cancer. Although most of the nonessential Genome Instability Suppressing (GIS) genes in Saccharomyces cerevisiae are known, the essential genes in which mutations can cause increased GCR rates are not well understood. Here 2 S. cerevisiae GCR assays were used to screen a targeted collection of temperature-sensitive mutants to identify mutations that caused increased GCR rates. This identified 94 essential GIS (eGIS) genes in which mutations cause increased GCR rates and 38 candidate eGIS genes that encode eGIS1 protein-interacting or family member proteins. Analysis of TCGA data using the human genes predicted to encode the proteins and protein complexes implicated by the S. cerevisiae eGIS genes revealed a significant enrichment of mutations affecting predicted human eGIS genes in 10 of the 16 cancers analyzed.

2.
Nat Commun ; 10(1): 3644, 2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31409799

RESUMO

B cell development is a highly regulated process involving multiple differentiation steps, yet many details regarding this pathway remain unknown. Sequencing of patients with B cell-restricted immunodeficiency reveals autosomal dominant mutations in TOP2B. TOP2B encodes a type II topoisomerase, an essential gene required to alleviate topological stress during DNA replication and gene transcription, with no previously known role in B cell development. We use Saccharomyces cerevisiae, and knockin and knockout murine models, to demonstrate that patient mutations in TOP2B have a dominant negative effect on enzyme function, resulting in defective proliferation, survival of B-2 cells, causing a block in B cell development, and impair humoral function in response to immunization.

3.
Hum Mutat ; 2018 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-30461124

RESUMO

The epithelial cell adhesion molecule gene (EPCAM, previously known as TACSTD1 or TROP1) encodes a membrane-bound protein that is localized to the basolateral membrane of epithelial cells and is overexpressed in some tumors. Biallelic mutations in EPCAM cause congenital tufting enteropathy (CTE), which is a rare chronic diarrheal disorder presenting in infancy. Monoallelic deletions of the 3' end of EPCAM that silence the downstream gene, MSH2, cause a form of Lynch syndrome, which is a cancer predisposition syndrome associated with loss of DNA mismatch repair. Here, we report 13 novel EPCAM mutations from 17 CTE patients from two separate centers, review EPCAM mutations associated with CTE and Lynch syndrome, and structurally model pathogenic missense mutations. Statistical analyses indicate that the c.499dupC (previously reported as c.498insC) frameshift mutation was associated with more severe treatment regimens and greater mortality in CTE, whereas the c.556-14A>G and c.491+1G>A splice site mutations were not correlated with treatments or outcomes significantly different than random simulation. These findings suggest that genotype-phenotype correlations may be useful in contributing to management decisions of CTE patients. Depending on the type and nature of EPCAM mutation, one of two unrelated diseases may occur, CTE or Lynch syndrome.

4.
J Biol Chem ; 293(47): 18055-18070, 2018 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-30237169

RESUMO

DNA mismatch repair (MMR) corrects mispaired DNA bases and small insertion/deletion loops generated by DNA replication errors. After binding a mispair, the eukaryotic mispair recognition complex Msh2-Msh6 binds ATP in both of its nucleotide-binding sites, which induces a conformational change resulting in the formation of an Msh2-Msh6 sliding clamp that releases from the mispair and slides freely along the DNA. However, the roles that Msh2-Msh6 sliding clamps play in MMR remain poorly understood. Here, using Saccharomyces cerevisiae, we created Msh2 and Msh6 Walker A nucleotide-binding site mutants that have defects in ATP binding in one or both nucleotide-binding sites of the Msh2-Msh6 heterodimer. We found that these mutations cause a complete MMR defect in vivo The mutant Msh2-Msh6 complexes exhibited normal mispair recognition and were proficient at recruiting the MMR endonuclease Mlh1-Pms1 to mispaired DNA. At physiological (2.5 mm) ATP concentration, the mutant complexes displayed modest partial defects in supporting MMR in reconstituted Mlh1-Pms1-independent and Mlh1-Pms1-dependent MMR reactions in vitro and in activation of the Mlh1-Pms1 endonuclease and showed a more severe defect at low (0.1 mm) ATP concentration. In contrast, five of the mutants were completely defective and one was mostly defective for sliding clamp formation at high and low ATP concentrations. These findings suggest that mispair-dependent sliding clamp formation triggers binding of additional Msh2-Msh6 complexes and that further recruitment of additional downstream MMR proteins is required for signal amplification of mispair binding during MMR.

5.
Nat Commun ; 9(1): 3680, 2018 09 11.
Artigo em Inglês | MEDLINE | ID: mdl-30206225

RESUMO

Genome instability is associated with tumorigenesis. Here, we identify a role for the histone Htz1, which is deposited by the Swr1 chromatin-remodeling complex (SWR-C), in preventing genome instability in the absence of the replication fork/replication checkpoint proteins Mrc1, Csm3, or Tof1. When combined with deletion of SWR1 or HTZ1, deletion of MRC1, CSM3, or TOF1 or a replication-defective mrc1 mutation causes synergistic increases in gross chromosomal rearrangement (GCR) rates, accumulation of a broad spectrum of GCRs, and hypersensitivity to replication stress. The double mutants have severe replication defects and accumulate aberrant replication intermediates. None of the individual mutations cause large increases in GCR rates; however, defects in MRC1, CSM3 or TOF1 cause activation of the DNA damage checkpoint and replication defects. We propose a model in which Htz1 deposition and retention in chromatin prevents transiently stalled replication forks that occur in mrc1, tof1, or csm3 mutants from being converted to DNA double-strand breaks that trigger genome instability.

6.
Nat Struct Mol Biol ; 25(8): 650-659, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30061603

RESUMO

Eukaryotic DNA mismatch repair (MMR) involves both exonuclease 1 (Exo1)-dependent and Exo1-independent pathways. We found that the unstructured C-terminal domain of Saccharomyces cerevisiae Exo1 contains two MutS homolog 2 (Msh2)-interacting peptide (SHIP) boxes downstream from the MutL homolog 1 (Mlh1)-interacting peptide (MIP) box. These three sites were redundant in Exo1-dependent MMR in vivo and could be replaced by a fusion protein between an N-terminal fragment of Exo1 and Msh6. The SHIP-Msh2 interactions were eliminated by the msh2M470I mutation, and wild-type but not mutant SHIP peptides eliminated Exo1-dependent MMR in vitro. We identified two S. cerevisiae SHIP-box-containing proteins and three candidate human SHIP-box-containing proteins. One of these, Fun30, had a small role in Exo1-dependent MMR in vivo. The Remodeling of the Structure of Chromatin (Rsc) complex also functioned in both Exo1-dependent and Exo1-independent MMR in vivo. Our results identified two modes of Exo1 recruitment and a peptide module that mediates interactions between Msh2 and other proteins, and they support a model in which Exo1 functions in MMR by being tethered to the Msh2-Msh6 complex.

7.
PLoS Genet ; 14(3): e1007250, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29505562

RESUMO

Mms21, a subunit of the Smc5/6 complex, possesses an E3 ligase activity for the Small Ubiquitin-like MOdifier (SUMO). Here we show that the mms21-CH mutation, which inactivates Mms21 ligase activity, causes increased accumulation of gross chromosomal rearrangements (GCRs) selected in the dGCR assay. These dGCRs are formed by non-allelic homologous recombination between divergent DNA sequences mediated by Rad52-, Rrm3- and Pol32-dependent break-induced replication. Combining mms21-CH with sgs1Δ caused a synergistic increase in GCRs rates, indicating the distinct roles of Mms21 and Sgs1 in suppressing GCRs. The mms21-CH mutation also caused increased rates of accumulating uGCRs mediated by breakpoints in unique sequences as revealed by whole genome sequencing. Consistent with the accumulation of endogenous DNA lesions, mms21-CH mutants accumulate increased levels of spontaneous Rad52 and Ddc2 foci and had a hyper-activated DNA damage checkpoint. Together, these findings support that Mms21 prevents the accumulation of spontaneous DNA lesions that cause diverse GCRs.


Assuntos
Dano ao DNA/genética , Proteína SUMO-1/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/genética , Cromossomos Fúngicos , Reparo do DNA , DNA Polimerase Dirigida por DNA/genética , DNA Polimerase Dirigida por DNA/metabolismo , Endodesoxirribonucleases/genética , Endodesoxirribonucleases/metabolismo , Epistasia Genética , Exodesoxirribonucleases/genética , Exodesoxirribonucleases/metabolismo , Genoma Fúngico , Mutação , Proteína Rad52 de Recombinação e Reparo de DNA/metabolismo , RecQ Helicases/genética , RecQ Helicases/metabolismo , Proteína SUMO-1/genética , Proteínas de Saccharomyces cerevisiae/genética
8.
PLoS Genet ; 14(1): e1007170, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29320491

RESUMO

Defects in the genes encoding the Paf1 complex can cause increased genome instability. Loss of Paf1, Cdc73, and Ctr9, but not Rtf1 or Leo1, caused increased accumulation of gross chromosomal rearrangements (GCRs). Combining the cdc73Δ mutation with individual deletions of 43 other genes, including TEL1 and YKU80, which are involved in telomere maintenance, resulted in synergistic increases in GCR rates. Whole genome sequence analysis of GCRs indicated that there were reduced relative rates of GCRs mediated by de novo telomere additions and increased rates of translocations and inverted duplications in cdc73Δ single and double mutants. Analysis of telomere lengths and telomeric gene silencing in strains containing different combinations of cdc73Δ, tel1Δ and yku80Δ mutations suggested that combinations of these mutations caused increased defects in telomere maintenance. A deletion analysis of Cdc73 revealed that a central 105 amino acid region was necessary and sufficient for suppressing the defects observed in cdc73Δ strains; this region was required for the binding of Cdc73 to the Paf1 complex through Ctr9 and for nuclear localization of Cdc73. Taken together, these data suggest that the increased GCR rate of cdc73Δ single and double mutants is due to partial telomere dysfunction and that Ctr9 and Paf1 play a central role in the Paf1 complex potentially by scaffolding the Paf1 complex subunits or by mediating recruitment of the Paf1 complex to the different processes it functions in.


Assuntos
Instabilidade Genômica/genética , Proteínas Nucleares/fisiologia , Proteínas de Saccharomyces cerevisiae/fisiologia , Homeostase do Telômero/genética , Proteínas de Ciclo Celular/genética , Proteínas de Ligação a DNA/fisiologia , Peptídeos e Proteínas de Sinalização Intracelular/fisiologia , Proteínas Nucleares/genética , Organismos Geneticamente Modificados , Fenótipo , Ligação Proteica , Proteínas Serina-Treonina Quinases/fisiologia , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Telômero/metabolismo , Fatores de Elongação da Transcrição/genética
9.
Methods Mol Biol ; 1672: 43-61, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29043616

RESUMO

Genome rearrangements underlie different human diseases including many cancers. Determining the rates at which genome rearrangements arise and isolating unique, independent genome rearrangements is critical to understanding the genes and pathways that prevent or promote genome rearrangements. Here, we describe quantitative S. cerevisiae genetic assays for measuring the rates of accumulating genome rearrangements including deletions, translocations, and broken chromosomes healed by de novo telomere addition that result in the deletion of two counter-selectable genes, CAN1 and URA3, placed in the nonessential regions of the S. cerevisiae genome. The assays also allow for the isolation of individual genome rearrangements for structural studies, and a method for analyzing genome rearrangements by next-generation DNA sequencing is provided.


Assuntos
Genoma Fúngico , Genômica , Recombinação Genética , Saccharomyces cerevisiae/genética , Instabilidade Genômica , Biblioteca Genômica , Genômica/métodos , Deleção de Sequência , Translocação Genética , Sequenciamento Completo do Genoma
10.
Genetics ; 206(3): 1187-1225, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28684602

RESUMO

Genome rearrangements result in mutations that underlie many human diseases, and ongoing genome instability likely contributes to the development of many cancers. The tools for studying genome instability in mammalian cells are limited, whereas model organisms such as Saccharomyces cerevisiae are more amenable to these studies. Here, we discuss the many genetic assays developed to measure the rate of occurrence of Gross Chromosomal Rearrangements (called GCRs) in S. cerevisiae These genetic assays have been used to identify many types of GCRs, including translocations, interstitial deletions, and broken chromosomes healed by de novo telomere addition, and have identified genes that act in the suppression and formation of GCRs. Insights from these studies have contributed to the understanding of pathways and mechanisms that suppress genome instability and how these pathways cooperate with each other. Integrated models for the formation and suppression of GCRs are discussed.


Assuntos
Genoma Fúngico , Instabilidade Genômica , Saccharomyces cerevisiae/genética , Aberrações Cromossômicas , Rearranjo Gênico
11.
J Appl Crystallogr ; 49(Pt 5): 1412-1419, 2016 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-27738411

RESUMO

The Guinier region in small-angle X-ray scattering (SAXS) defines the radius of gyration, Rg, and the forward scattering intensity, I(0). In Guinier peak analysis (GPA), the plot of qI(q) versus q2 transforms the Guinier region into a characteristic peak for visual and automated inspection of data. Deviations of the peak position from the theoretical position in dimensionless GPA plots can suggest parameter errors, problematic low-resolution data, some kinds of intermolecular interactions or elongated scatters. To facilitate automated analysis by GPA, the elongation ratio (ER), which is the ratio of the areas in the pair-distribution function P(r) after and before the P(r) maximum, was characterized; symmetric samples have ER values around 1, and samples with ER values greater than 5 tend to be outliers in GPA analysis. Use of GPA+ER can be a helpful addition to SAXS data analysis pipelines.

12.
PLoS Genet ; 12(8): e1006302, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27579875

RESUMO

[This corrects the article DOI: 10.1371/journal.pgen.1003670.].

13.
Nat Commun ; 7: 11256, 2016 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-27071721

RESUMO

Gross chromosomal rearrangements (GCRs) play an important role in human diseases, including cancer. The identity of all Genome Instability Suppressing (GIS) genes is not currently known. Here multiple Saccharomyces cerevisiae GCR assays and query mutations were crossed into arrays of mutants to identify progeny with increased GCR rates. One hundred eighty two GIS genes were identified that suppressed GCR formation. Another 438 cooperatively acting GIS genes were identified that were not GIS genes, but suppressed the increased genome instability caused by individual query mutations. Analysis of TCGA data using the human genes predicted to act in GIS pathways revealed that a minimum of 93% of ovarian and 66% of colorectal cancer cases had defects affecting one or more predicted GIS gene. These defects included loss-of-function mutations, copy-number changes associated with reduced expression, and silencing. In contrast, acute myeloid leukaemia cases did not appear to have defects affecting the predicted GIS genes.


Assuntos
Rearranjo Gênico/genética , Redes Reguladoras de Genes , Genoma Fúngico , Neoplasias/genética , Saccharomyces cerevisiae/genética , Cromossomos Fúngicos/genética , Elementos Facilitadores Genéticos/genética , Epistasia Genética , Genes Fúngicos , Instabilidade Genômica , Humanos , Mutação/genética
14.
DNA Repair (Amst) ; 38: 32-41, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26698649

RESUMO

DNA mismatch repair (MMR) repairs mispaired bases in DNA generated by replication errors. MutS or MutS homologs recognize mispairs and coordinate with MutL or MutL homologs to direct excision of the newly synthesized DNA strand. In most organisms, the signal that discriminates between the newly synthesized and template DNA strands has not been definitively identified. In contrast, Escherichia coli and some related gammaproteobacteria use a highly elaborated methyl-directed MMR system that recognizes Dam methyltransferase modification sites that are transiently unmethylated on the newly synthesized strand after DNA replication. Evolution of methyl-directed MMR is characterized by the acquisition of Dam and the MutH nuclease and by the loss of the MutL endonuclease activity. Methyl-directed MMR is present in a subset of Gammaproteobacteria belonging to the orders Enterobacteriales, Pasteurellales, Vibrionales, Aeromonadales, and a subset of the Alteromonadales (the EPVAA group) as well as in gammaproteobacteria that have obtained these genes by horizontal gene transfer, including the medically relevant bacteria Fluoribacter, Legionella, and Tatlockia and the marine bacteria Methylophaga and Nitrosococcus.


Assuntos
Evolução Biológica , Reparo de Erro de Pareamento de DNA , Escherichia coli/metabolismo , Sequência de Aminoácidos , Transferência Genética Horizontal/genética , Metilação , Dados de Sequência Molecular , Filogenia
15.
DNA Repair (Amst) ; 32: 24-32, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25956862

RESUMO

DNA mismatch repair (MMR) acts to repair mispaired bases resulting from misincorporation errors during DNA replication and also recognizes mispaired bases in recombination (HR) intermediates. Exonuclease 1 (Exo1) is a 5' → 3' exonuclease that participates in a number of DNA repair pathways. Exo1 was identified as an exonuclease that participates in Saccharomyces cerevisiae and human MMR where it functions to excise the daughter strand after mispair recognition, and additionally Exo1 functions in end resection during HR. However, Exo1 is not absolutely required for end resection during HR in vivo. Similarly, while Exo1 is required in MMR reactions that have been reconstituted in vitro, genetics studies have shown that it is not absolutely required for MMR in vivo suggesting the existence of Exo1-independent and Exo1-dependent MMR subpathways. Here, we review what is known about the Exo1-independent and Exo1-dependent subpathways, including studies of mutations in MMR genes that specifically disrupt either subpathway.


Assuntos
Reparo de Erro de Pareamento de DNA , DNA Fúngico/química , Exodesoxirribonucleases/química , Regulação Fúngica da Expressão Gênica , Saccharomyces cerevisiae/enzimologia , Pareamento Incorreto de Bases , Quebras de DNA de Cadeia Dupla , Replicação do DNA , DNA Fúngico/metabolismo , Exodesoxirribonucleases/genética , Exodesoxirribonucleases/metabolismo , Humanos , Modelos Moleculares , Mutação , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Saccharomyces cerevisiae/genética
16.
Mol Cell ; 55(2): 291-304, 2014 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-24981171

RESUMO

Genetic evidence has implicated multiple pathways in eukaryotic DNA mismatch repair (MMR) downstream of mispair recognition and Mlh1-Pms1 recruitment, including Exonuclease 1 (Exo1)-dependent and -independent pathways. We identified 14 mutations in POL30, which encodes PCNA in Saccharomyces cerevisiae, specific to Exo1-independent MMR. The mutations identified affected amino acids at three distinct sites on the PCNA structure. Multiple mutant PCNA proteins had defects either in trimerization and Msh2-Msh6 binding or in activation of the Mlh1-Pms1 endonuclease that initiates excision during MMR. The latter class of mutations led to hyperaccumulation of repair intermediate Mlh1-Pms1 foci and were enhanced by an msh6 mutation that disrupted the Msh2-Msh6 interaction with PCNA. These results reveal a central role for PCNA in the Exo1-independent MMR pathway and suggest that Msh2-Msh6 localizes PCNA to repair sites after mispair recognition to activate the Mlh1-Pms1 endonuclease for initiating Exo1-dependent repair or for driving progressive excision in Exo1-independent repair.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteínas de Transporte/metabolismo , Proteínas de Ligação a DNA/metabolismo , Exodesoxirribonucleases/metabolismo , Proteína 2 Homóloga a MutS/metabolismo , Antígeno Nuclear de Célula em Proliferação/genética , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/enzimologia , Reparo de Erro de Pareamento de DNA , DNA Fúngico/genética , Ativação Enzimática , Modelos Moleculares , Proteína 1 Homóloga a MutL , Proteínas MutL , Mutação de Sentido Incorreto , Antígeno Nuclear de Célula em Proliferação/química , Antígeno Nuclear de Célula em Proliferação/metabolismo , Ligação Proteica , Domínios e Motivos de Interação entre Proteínas , Multimerização Proteica , Estabilidade Proteica , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/química , Transdução de Sinais
17.
PLoS Genet ; 10(5): e1004327, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24811092

RESUMO

In Saccharomyces cerevisiae, the essential mismatch repair (MMR) endonuclease Mlh1-Pms1 forms foci promoted by Msh2-Msh6 or Msh2-Msh3 in response to mispaired bases. Here we analyzed the Mlh1-Mlh2 complex, whose role in MMR has been unclear. Mlh1-Mlh2 formed foci that often colocalized with and had a longer lifetime than Mlh1-Pms1 foci. Mlh1-Mlh2 foci were similar to Mlh1-Pms1 foci: they required mispair recognition by Msh2-Msh6, increased in response to increased mispairs or downstream defects in MMR, and formed after induction of DNA damage by phleomycin but not double-stranded breaks by I-SceI. Mlh1-Mlh2 could be recruited to mispair-containing DNA in vitro by either Msh2-Msh6 or Msh2-Msh3. Deletion of MLH2 caused a synergistic increase in mutation rate in combination with deletion of MSH6 or reduced expression of Pms1. Phylogenetic analysis demonstrated that the S. cerevisiae Mlh2 protein and the mammalian PMS1 protein are homologs. These results support a hypothesis that Mlh1-Mlh2 is a non-essential accessory factor that acts to enhance the activity of Mlh1-Pms1.


Assuntos
Pareamento Incorreto de Bases , DNA Fúngico/genética , Proteínas Nucleares/fisiologia , Proteínas de Saccharomyces cerevisiae/fisiologia , Saccharomyces cerevisiae/genética , Proteínas de Transporte/fisiologia , Dano ao DNA , Mutação da Fase de Leitura , Proteínas MutL
18.
PLoS Genet ; 10(4): e1004277, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24699249

RESUMO

Whole genome sequencing of cancer genomes has revealed a diversity of recurrent gross chromosomal rearrangements (GCRs) that are likely signatures of specific defects in DNA damage response pathways. However, inferring the underlying defects has been difficult due to insufficient information relating defects in DNA metabolism to GCR signatures. By analyzing over 95 mutant strains of Saccharomyces cerevisiae, we found that the frequency of GCRs that deleted an internal CAN1/URA3 cassette on chrV L while retaining a chrV L telomeric hph marker was significantly higher in tel1Δ, sae2Δ, rad53Δ sml1Δ, and mrc1Δ tof1Δ mutants. The hph-retaining GCRs isolated from tel1Δ mutants contained either an interstitial deletion dependent on non-homologous end-joining or an inverted duplication that appeared to be initiated from a double strand break (DSB) on chrV L followed by hairpin formation, copying of chrV L from the DSB toward the centromere, and homologous recombination to capture the hph-containing end of chrV L. In contrast, hph-containing GCRs from other mutants were primarily interstitial deletions (mrc1Δ tof1Δ) or inverted duplications (sae2Δ and rad53Δ sml1Δ). Mutants with impaired de novo telomere addition had increased frequencies of hph-containing GCRs, whereas mutants with increased de novo telomere addition had decreased frequencies of hph-containing GCRs. Both types of hph-retaining GCRs occurred in wild-type strains, suggesting that the increased frequencies of hph retention were due to the relative efficiencies of competing DNA repair pathways. Interestingly, the inverted duplications observed here resemble common GCRs in metastatic pancreatic cancer.


Assuntos
Cromossomos Fúngicos/genética , Reparo do DNA/genética , Endonucleases/genética , Rearranjo Gênico/genética , Peptídeos e Proteínas de Sinalização Intracelular/genética , Proteínas Serina-Treonina Quinases/genética , Proteínas de Saccharomyces cerevisiae/genética , Telômero/genética , Dano ao DNA/genética , Genoma Fúngico/genética , Mutação/genética , Recombinação Genética/genética , Saccharomyces cerevisiae/genética
19.
Mol Cell Biol ; 34(8): 1521-34, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24550002

RESUMO

Errors during DNA replication are one likely cause of gross chromosomal rearrangements (GCRs). Here, we analyze the role of RNase H2, which functions to process Okazaki fragments, degrade transcription intermediates, and repair misincorporated ribonucleotides, in preventing genome instability. The results demonstrate that rnh203 mutations result in a weak mutator phenotype and cause growth defects and synergistic increases in GCR rates when combined with mutations affecting other DNA metabolism pathways, including homologous recombination (HR), sister chromatid HR, resolution of branched HR intermediates, postreplication repair, sumoylation in response to DNA damage, and chromatin assembly. In some cases, a mutation in RAD51 or TOP1 suppressed the increased GCR rates and/or the growth defects of rnh203Δ double mutants. This analysis suggests that cells with RNase H2 defects have increased levels of DNA damage and depend on other pathways of DNA metabolism to overcome the deleterious effects of this DNA damage.


Assuntos
Instabilidade Genômica/fisiologia , Ribonuclease H/metabolismo , Saccharomyces cerevisiae/enzimologia , Animais , Dano ao DNA/fisiologia , Reparo do DNA/fisiologia , Replicação do DNA/fisiologia , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Mutação/genética , Recombinação Genética/genética , Recombinação Genética/imunologia , Ribonuclease H/genética , Saccharomyces cerevisiae/genética
20.
PLoS Genet ; 9(10): e1003869, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-24204293

RESUMO

Lynch syndrome (hereditary nonpolypsis colorectal cancer or HNPCC) is a common cancer predisposition syndrome. Predisposition to cancer in this syndrome results from increased accumulation of mutations due to defective mismatch repair (MMR) caused by a mutation in one of the mismatch repair genes MLH1, MSH2, MSH6 or PMS2/scPMS1. To better understand the function of Mlh1-Pms1 in MMR, we used Saccharomyces cerevisiae to identify six pms1 mutations (pms1-G683E, pms1-C817R, pms1-C848S, pms1-H850R, pms1-H703A and pms1-E707A) that were weakly dominant in wild-type cells, which surprisingly caused a strong MMR defect when present on low copy plasmids in an exo1Δ mutant. Molecular modeling showed these mutations caused amino acid substitutions in the metal coordination pocket of the Pms1 endonuclease active site and biochemical studies showed that they inactivated the endonuclease activity. This model of Mlh1-Pms1 suggested that the Mlh1-FERC motif contributes to the endonuclease active site. Consistent with this, the mlh1-E767stp mutation caused both MMR and endonuclease defects similar to those caused by the dominant pms1 mutations whereas mutations affecting the predicted metal coordinating residue Mlh1-C769 had no effect. These studies establish that the Mlh1-Pms1 endonuclease is required for MMR in a previously uncharacterized Exo1-independent MMR pathway.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas de Transporte/genética , Reparo de Erro de Pareamento de DNA/genética , Proteínas de Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteínas de Transporte/metabolismo , Domínio Catalítico/genética , Neoplasias Colorretais Hereditárias sem Polipose/genética , Neoplasias Colorretais Hereditárias sem Polipose/patologia , Proteínas de Ligação a DNA/genética , Exodesoxirribonucleases/metabolismo , Humanos , Proteína 1 Homóloga a MutL , Proteínas MutL , Mutação , Estrutura Terciária de Proteína , Saccharomyces cerevisiae/crescimento & desenvolvimento , Proteínas de Saccharomyces cerevisiae/metabolismo , Transdução de Sinais
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA