scholarly journals The SRS2 suppressor of rad6 mutations of Saccharomyces cerevisiae acts by channeling DNA lesions into the RAD52 DNA repair pathway.

Genetics ◽  
1990 ◽  
Vol 124 (4) ◽  
pp. 817-831 ◽  
Author(s):  
R H Schiestl ◽  
S Prakash ◽  
L Prakash
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Repair ◽  
Gamma Ray ◽  
Dna Lesions ◽  
Recombinational Repair ◽  
Repair Pathway ◽  
Uv Mutagenesis ◽  
Uv Sensitivity ◽  
Suppressor Mutations ◽  
Induced Mutagenesis

Abstract rad6 mutants of Saccharomyces cerevisiae are defective in the repair of damaged DNA, DNA damage induced mutagenesis, and sporulation. In order to identify genes that can substitute for RAD6 function, we have isolated genomic suppressors of the UV sensitivity of rad6 deletion (rad6 delta) mutations and show that they also suppress the gamma-ray sensitivity but not the UV mutagenesis or sporulation defects of rad6. The suppressors show semidominance for suppression of UV sensitivity and dominance for suppression of gamma-ray sensitivity. The six suppressor mutations we isolated are all alleles of the same locus and are also allelic to a previously described suppressor of the rad6-1 nonsense mutation, SRS2. We show that suppression of rad6 delta is dependent on the RAD52 recombinational repair pathway since suppression is not observed in the rad6 delta SRS2 strain containing an additional mutation in either the RAD51, RAD52, RAD54, RAD55 or RAD57 genes. Possible mechanisms by which SRS2 may channel unrepaired DNA lesions into the RAD52 DNA repair pathway are discussed.

scholarly journals Effect of bacterial recA expression on DNA repair in the rad51 and rad52 mutants of Saccharomyces cerevisiae

1998 ◽  
Vol 21 (1) ◽  
pp. 3-10 ◽  
Author(s):  
M.A. Morais Jr. ◽  
V. Vlcková ◽  
I. Fridrichová ◽  
M. Slaninová ◽  
J. Brozmanová ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Repair ◽  
Uv Light ◽  
Dna Lesions ◽  
Reca Gene ◽  
Methyl Methane Sulfonate ◽  
Functional Homology ◽  
Uva Irradiation ◽  
Induced Mutagenesis ◽  
Mutant Cells

Molecular and functional homology between yeast proteins pRad51 and pRad52 and Escherichia coli pRecA involved in recombinational DNA repair led us to investigate possible effects of recA gene expression on DNA repair in rad51 and rad52 mutants of Saccharomyces cerevisiae. The mutant cells were subjected to one of the following treatments: preincubation with 8-methoxypsoralen and subsequent irradiation with 360-nm ultraviolet (UVA) (8-MOP + UVA), irradiation with 254-nm UV light or treatment with methyl methane sulfonate (MMS). While recA expression did not repair lethal DNA lesions in mutant rad51, it was able to partially restore resistance to 8-MOP + UVA and MMS in rad52. Expression of recA could not complement the sensitivity of rad51rad52 double mutants, indicating that pRad51 may be essential for the repair-stimulating activity of pRecA in the rad52 mutant. Spontaneous mutagenesis was increased, and 8-MOP-photoinduced mutagenesis was decreased by the presence of pRecA in rad52, whereas pRecA decreased UV-induced mutagenesis in rad51. Thus, pRecA may function in yeast DNA repair either as a member of a protein complex or as an individual protein that binds to mutagen-damaged DNA.

scholarly journals Dissection of the Functions of the Saccharomyces cerevisiae RAD6 Postreplicative Repair Group in Mutagenesis and UV Sensitivity

Genetics ◽  
2001 ◽  
Vol 159 (3) ◽  
pp. 953-963 ◽  
Author(s):  
Petr Ćejka ◽  
Vladimír Vondrejs ◽  
Zuzana Storchová
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Repair ◽  
Relative Importance ◽  
Repair Pathway ◽  
Spontaneous Mutagenesis ◽  
Uv Sensitivity ◽  
Rad6 Gene ◽  
Repair Pathways ◽  
Repair Group ◽  
Epistatic Analysis

Abstract The RAD6 postreplicative repair group participates in various processes of DNA metabolism. To elucidate the contribution of RAD6 to starvation-associated mutagenesis, which occurs in nongrowing cells cultivated under selective conditions, we analyzed the phenotype of strains expressing various alleles of the RAD6 gene and single and multiple mutants of the RAD6, RAD5, RAD18, REV3, and MMS2 genes from the RAD6 repair group. Our results show that the RAD6 repair pathway is also active in starving cells and its contribution to starvation-associated mutagenesis is similar to that of spontaneous mutagenesis. Epistatic analysis based on both spontaneous and starvation-associated mutagenesis and UV sensitivity showed that the RAD6 repair group consists of distinct repair pathways of different relative importance requiring, besides the presence of Rad6, also either Rad18 or Rad5 or both. We postulate the existence of four pathways: (1) nonmutagenic Rad5/Rad6/Rad18, (2) mutagenic Rad5/Rad6 /Rev3, (3) mutagenic Rad6/Rad18/Rev3, and (4) Rad6/Rad18/Rad30. Furthermore, we show that the high mutation rate observed in rad6 mutants is caused by a mutator different from Rev3. From our data and data previously published, we suggest a role for Rad6 in DNA repair and mutagenesis and propose a model for the RAD6 postreplicative repair group.

A Requirement for Recombinational Repair in Saccharomyces cerevisiae Is Caused by DNA Replication Defects of mec1 Mutants

Genetics ◽  
1999 ◽  
Vol 153 (2) ◽  
pp. 595-605 ◽  
Author(s):  
Bradley J Merrill ◽  
Connie Holm
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Synthetic Lethality ◽  
Velocity Sedimentation ◽  
Recombinational Repair ◽  
Repair Pathway ◽  
Dna Breaks ◽  
Single Stranded Dna ◽  
Double Stranded Dna

Abstract To examine the role of the RAD52 recombinational repair pathway in compensating for DNA replication defects in Saccharomyces cerevisiae, we performed a genetic screen to identify mutants that require Rad52p for viability. We isolated 10 mec1 mutations that display synthetic lethality with rad52. These mutations (designated mec1-srf for synthetic lethality with rad-fifty-two) simultaneously cause two types of phenotypes: defects in the checkpoint function of Mec1p and defects in the essential function of Mec1p. Velocity sedimentation in alkaline sucrose gradients revealed that mec1-srf mutants accumulate small single-stranded DNA synthesis intermediates, suggesting that Mec1p is required for the normal progression of DNA synthesis. sml1 suppressor mutations suppress both the accumulation of DNA synthesis intermediates and the requirement for Rad52p in mec1-srf mutants, but they do not suppress the checkpoint defect in mec1-srf mutants. Thus, it appears to be the DNA replication defects in mec1-srf mutants that cause the requirement for Rad52p. By using hydroxyurea to introduce similar DNA replication defects, we found that single-stranded DNA breaks frequently lead to double-stranded DNA breaks that are not rapidly repaired in rad52 mutants. Taken together, these data suggest that the RAD52 recombinational repair pathway is required to prevent or repair double-stranded DNA breaks caused by defective DNA replication in mec1-srf mutants.

Semidominant suppressors of Srs2 helicase mutations of Saccharomyces cerevisiae map in the RAD51 gene, whose sequence predicts a protein with similarities to procaryotic RecA proteins

1992 ◽  
Vol 12 (7) ◽  
pp. 3224-3234 ◽  
Author(s):  
A Aboussekhra ◽  
R Chanet ◽  
A Adjiri ◽  
F Fabre
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Gamma Ray ◽  
Genetic Recombination ◽  
Reca Protein ◽  
Radiation Sensitivity ◽  
Recombinational Repair ◽  
Lacz Gene ◽  
Sequence Comparisons ◽  
Rad51 Gene ◽  
Srs2 Helicase

Eleven suppressors of the radiation sensitivity of Saccharomyces cerevisiae diploids lacking the Srs2 helicase were analyzed and found to contain codominant mutations in the RAD51 gene known to be involved in recombinational repair and in genetic recombination. These mutant alleles confer an almost complete block in recombinational repair, as does deletion of RAD51, but heterozygous mutant alleles suppress the defects of srs2::LEU2 cells and are semidominant in Srs2+ cells. The results of this study are interpreted to mean that wild-type Rad51 protein binds to single-stranded DNA and that the semidominant mutations do not prevent this binding. The cloning and sequencing of RAD51 indicated that the gene encodes a predicted 400-amino-acid protein with a molecular mass of 43 kDa. Sequence comparisons revealed homologies to domains of Escherichia coli RecA protein predicted to be involved in DNA binding, ATP binding, and ATP hydrolysis. The expression of RAD51, measured with a RAD51-lacZ gene fusion, was found to be UV- and gamma-ray-inducible, with dose-dependent responses.

scholarly journals Effect of SOS-induced Pol II, Pol IV, and Pol V DNA polymerases on UV-induced mutagenesis and MFD repair in Escherichia coli cells.

2005 ◽  
Vol 52 (1) ◽  
pp. 139-147
Author(s):  
Michał Wrzesiński ◽  
Anetta Nowosielska ◽  
Jadwiga Nieminuszczy ◽  
Elzbieta Grzesiuk
Keyword(s):  
Escherichia Coli ◽  
Uv Light ◽  
Dna Polymerases ◽  
Dna Lesions ◽  
Uv Mutagenesis ◽  
Pol Ii ◽  
Pol Iv ◽  
Pol V ◽  
Induced Mutagenesis ◽  
Pol Iii

Irradiation of organisms with UV light produces genotoxic and mutagenic lesions in DNA. Replication through these lesions (translesion DNA synthesis, TSL) in Escherichia coli requires polymerase V (Pol V) and polymerase III (Pol III) holoenzyme. However, some evidence indicates that in the absence of Pol V, and with Pol III inactivated in its proofreading activity by the mutD5 mutation, efficient TSL takes place. The aim of this work was to estimate the involvement of SOS-inducible DNA polymerases, Pol II, Pol IV and Pol V, in UV mutagenesis and in mutation frequency decline (MFD), a mechanism of repair of UV-induced damage to DNA under conditions of arrested protein synthesis. Using the argE3-->Arg(+) reversion to prototrophy system in E. coli AB1157, we found that the umuDC-encoded Pol V is the only SOS-inducible polymerase required for UV mutagenesis, since in its absence the level of Arg(+) revertants is extremely low and independent of Pol II and/or Pol IV. The low level of UV-induced Arg(+) revertants observed in the AB1157mutD5DumuDC strain indicates that under conditions of disturbed proofreading activity of Pol III and lack of Pol V, UV-induced lesions are bypassed without inducing mutations. The presented results also indicate that Pol V may provide substrates for MFD repair; moreover, we suggest that only those DNA lesions which result from umuDC-directed UV mutagenesis are subject to MFD repair.

scholarly journals Beta Human Papillomavirus 8E6 Attenuates Non-Homologous End Joining by Hindering DNA-PKcs Activity

Cancers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2356
Author(s):  
Changkun Hu ◽  
Taylor Bugbee ◽  
Monica Gamez ◽  
Nicholas A. Wallace
Keyword(s):  
Dna Repair ◽  
Viral Infections ◽  
Dna Lesions ◽  
Human Papillomaviruses ◽  
Molecular Evidence ◽  
Repair Pathway ◽  
End Joining ◽  
Dsb Repair ◽  
Dependent Protein ◽  
Non Homologous End Joining

Cutaneous viral infections occur in a background of near continual exposure to environmental genotoxins, like UV radiation in sunlight. Failure to repair damaged DNA is an established driver of tumorigenesis and substantial cellular resources are devoted to repairing DNA lesions. Beta-human papillomaviruses (β-HPVs) attenuate DNA repair signaling. However, their role in human disease is unclear. Some have proposed that β-HPV promotes tumorigenesis, while others suggest that β-HPV protects against skin cancer. Most of the molecular evidence that β-HPV impairs DNA repair has been gained via characterization of the E6 protein from β-HPV 8 (β-HPV 8E6). Moreover, β-HPV 8E6 hinders DNA repair by binding and destabilizing p300, a transcription factor for multiple DNA repair genes. By reducing p300 availability, β-HPV 8E6 attenuates a major double strand DNA break (DSB) repair pathway, homologous recombination. Here, β-HPV 8E6 impairs another DSB repair pathway, non-homologous end joining (NHEJ). Specifically, β-HPV 8E6 acts by attenuating DNA-dependent protein kinase (DNA-PK) activity, a critical NHEJ kinase. This includes DNA-PK activation and the downstream of steps in the pathway associated with DNA-PK activity. Notably, β-HPV 8E6 inhibits NHEJ through p300 dependent and independent means. Together, these data expand the known genome destabilizing capabilities of β-HPV 8E6.

scholarly journals An alternative eukaryotic DNA excision repair pathway.

1995 ◽  
Vol 15 (8) ◽  
pp. 4572-4577 ◽  
Author(s):  
G A Freyer ◽  
S Davey ◽  
J V Ferrer ◽  
A M Martin ◽  
D Beach ◽  
...  
Keyword(s):  
Dna Repair ◽  
Excision Repair ◽  
Uv Light ◽  
Repair Process ◽  
Dna Lesions ◽  
Repair Pathway ◽  
Cyclobutane Pyrimidine Dimers ◽  
Dna Excision Repair ◽  
Pyrimidine Dimers

DNA lesions induced by UV light, cyclobutane pyrimidine dimers, and (6-4)pyrimidine pyrimidones are known to be repaired by the process of nucleotide excision repair (NER). However, in the fission yeast Schizosaccharomyces pombe, studies have demonstrated that at least two mechanisms for excising UV photo-products exist; NER and a second, previously unidentified process. Recently we reported that S. pombe contains a DNA endonuclease, SPDE, which recognizes and cleaves at a position immediately adjacent to cyclobutane pyrimidine dimers and (6-4)pyrimidine pyrimidones. Here we report that the UV-sensitive S. pombe rad12-502 mutant lacks SPDE activity. In addition, extracts prepared from the rad12-502 mutant are deficient in DNA excision repair, as demonstrated in an in vitro excision repair assay. DNA repair activity was restored to wild-type levels in extracts prepared from rad12-502 cells by the addition of partially purified SPDE to in vitro repair reaction mixtures. When the rad12-502 mutant was crossed with the NER rad13-A mutant, the resulting double mutant was much more sensitive to UV radiation than either single mutant, demonstrating that the rad12 gene product functions in a DNA repair pathway distinct from NER. These data directly link SPDE to this alternative excision repair process. We propose that the SPDE-dependent DNA repair pathway is the second DNA excision repair process present in S. pombe.

scholarly journals Complex Formation with Rev1 Enhances the Proficiency of Saccharomyces cerevisiae DNA Polymerase ζ for Mismatch Extension and for Extension Opposite from DNA Lesions

2006 ◽  
Vol 26 (24) ◽  
pp. 9555-9563 ◽  
Author(s):  
Narottam Acharya ◽  
Robert E. Johnson ◽  
Satya Prakash ◽  
Louise Prakash
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Polymerase ◽  
Dna Lesions ◽  
Synthetic Activity ◽  
Lesion Bypass ◽  
Dna Lesion ◽  
C Terminus ◽  
Accessory Subunit ◽  
Induced Mutagenesis ◽  
Y Family

ABSTRACT Rev1, a Y family DNA polymerase (Pol) functions together with Polζ, a B family Pol comprised of the Rev3 catalytic subunit and Rev7 accessory subunit, in promoting translesion DNA synthesis (TLS). Extensive genetic studies with Saccharomyces cerevisiae have indicated a requirement of both Polζ and Rev1 for damage-induced mutagenesis, implicating their involvement in mutagenic TLS. Polζ is specifically adapted to promote the extension step of lesion bypass, as it proficiently extends primer termini opposite DNA lesions, and it is also a proficient extender of mismatched primer termini on undamaged DNAs. Since TLS through UV-induced lesions and various other DNA lesions does not depend upon the DNA-synthetic activity of Rev1, Rev1 must contribute to Polζ-dependent TLS in a nonenzymatic way. Here, we provide evidence for the physical association of Rev1 with Polζ and show that this binding is mediated through the C terminus of Rev1 and the polymerase domain of Rev3. Importantly, a rev1 mutant that lacks the C-terminal 72 residues which inactivate interaction with Rev3 exhibits the same high degree of UV sensitivity and defectiveness in UV-induced mutagenesis as that conferred by the rev1Δ mutation. We propose that Rev1 binding to Polζ is indispensable for the targeting of Polζ to the replication fork stalled at a DNA lesion. In addition to this structural role, Rev1 binding enhances the proficiency of Polζ for the extension of mismatched primer termini on undamaged DNAs and for the extension of primer termini opposite DNA lesions.

scholarly journals Semidominant suppressors of Srs2 helicase mutations of Saccharomyces cerevisiae map in the RAD51 gene, whose sequence predicts a protein with similarities to procaryotic RecA proteins.

1992 ◽  
Vol 12 (7) ◽  
pp. 3224-3234 ◽  
Author(s):  
A Aboussekhra ◽  
R Chanet ◽  
A Adjiri ◽  
F Fabre
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Gamma Ray ◽  
Genetic Recombination ◽  
Reca Protein ◽  
Radiation Sensitivity ◽  
Recombinational Repair ◽  
Lacz Gene ◽  
Sequence Comparisons ◽  
Rad51 Gene ◽  
Srs2 Helicase

Eleven suppressors of the radiation sensitivity of Saccharomyces cerevisiae diploids lacking the Srs2 helicase were analyzed and found to contain codominant mutations in the RAD51 gene known to be involved in recombinational repair and in genetic recombination. These mutant alleles confer an almost complete block in recombinational repair, as does deletion of RAD51, but heterozygous mutant alleles suppress the defects of srs2::LEU2 cells and are semidominant in Srs2+ cells. The results of this study are interpreted to mean that wild-type Rad51 protein binds to single-stranded DNA and that the semidominant mutations do not prevent this binding. The cloning and sequencing of RAD51 indicated that the gene encodes a predicted 400-amino-acid protein with a molecular mass of 43 kDa. Sequence comparisons revealed homologies to domains of Escherichia coli RecA protein predicted to be involved in DNA binding, ATP binding, and ATP hydrolysis. The expression of RAD51, measured with a RAD51-lacZ gene fusion, was found to be UV- and gamma-ray-inducible, with dose-dependent responses.

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