| 1. |
- Garbacz, Marta A., et al.
(författare)
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The absence of the catalytic domains of Saccharomyces cerevisiae DNA polymerase ϵ strongly reduces DNA replication fidelity
- 2019
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Ingår i: Nucleic Acids Research. - : Oxford University Press. - 0305-1048 .- 1362-4962. ; 47:8, s. 3986-3995
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Tidskriftsartikel (refereegranskat)abstract
- The four B-family DNA polymerases α, δ, ϵ and ζ cooperate to accurately replicate the eukaryotic nuclear genome. Here, we report that a Saccharomyces cerevisiae strain encoding the pol2-16 mutation that lacks Pol ϵ's polymerase and exonuclease activities has increased dNTP concentrations and an increased mutation rate at the CAN1 locus compared to wild type yeast. About half of this mutagenesis disappears upon deleting the REV3 gene encoding the catalytic subunit of Pol ζ. The remaining, still strong, mutator phenotype is synergistically elevated in an msh6Δ strain and has a mutation spectrum characteristic of mistakes made by Pol δ. The results support a model wherein slow-moving replication forks caused by the lack of Pol ϵ's catalytic domains result in greater involvement of mutagenic DNA synthesis by Pol ζ as well as diminished proofreading by Pol δ during replication.
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| 2. |
- Nick McElhinny, Stephanie A, et al.
(författare)
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Abundant ribonucleotide incorporation into DNA by yeast replicative polymerases.
- 2010
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 107:11, s. 4949-4954
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of nucleoside triphosphate levels in Saccharomyces cerevisiae reveal that the four rNTPs are in 36- to 190-fold molar excess over their corresponding dNTPs. During DNA synthesis in vitro using the physiological nucleoside triphosphate concentrations, yeast DNA polymerase epsilon, which is implicated in leading strand replication, incorporates one rNMP for every 1,250 dNMPs. Pol delta and Pol alpha, which conduct lagging strand replication, incorporate one rNMP for every 5,000 or 625 dNMPs, respectively. Discrimination against rNMP incorporation varies widely, in some cases by more than 100-fold, depending on the identity of the base and the template sequence context in which it is located. Given estimates of the amount of replication catalyzed by Pols alpha, delta, and epsilon, the results are consistent with the possibility that more than 10,000 rNMPs may be incorporated into the nuclear genome during each round of replication in yeast. Thus, rNMPs may be the most common noncanonical nucleotides introduced into the eukaryotic genome. Potential beneficial and negative consequences of abundant ribonucleotide incorporation into DNA are discussed, including the possibility that unrepaired rNMPs in DNA could be problematic because yeast DNA polymerase epsilon has difficulty bypassing a single rNMP present within a DNA template.
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| 3. |
- Nick McElhinny, Stephanie A, et al.
(författare)
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Genome instability due to ribonucleotide incorporation into DNA
- 2010
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Ingår i: Nature Chemical Biology. - : Springer Science and Business Media LLC. - 1552-4450 .- 1552-4469. ; 6:10, s. 774-81
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Tidskriftsartikel (refereegranskat)abstract
- Maintaining the chemical identity of DNA depends on ribonucleotide exclusion by DNA polymerases. However, ribonucleotide exclusion during DNA synthesis in vitro is imperfect. To determine whether ribonucleotides are incorporated during DNA replication in vivo, we substituted leucine or glycine for an active-site methionine in yeast DNA polymerase ϵ (Pol ϵ). Ribonucleotide incorporation in vitro was three-fold lower for M644L and 11-fold higher for M644G Pol ϵ compared to wild-type Pol ϵ. This hierarchy was recapitulated in vivo in yeast strains lacking RNase H2. Moreover, the pol2-M644G rnh201Δ strain progressed more slowly through S phase, had elevated dNTP pools and generated 2-5-base-pair deletions in repetitive sequences at a high rate and in a gene orientation-dependent manner. The data indicate that ribonucleotides are incorporated during replication in vivo, that they are removed by RNase H2-dependent repair and that defective repair results in replicative stress and genome instability via DNA strand misalignment.
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| 4. |
- Orebaugh, Clinton D, et al.
(författare)
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Mapping Ribonucleotides Incorporated into DNA by Hydrolytic End-Sequencing.
- 2018
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Ingår i: Methods in molecular biology (Clifton, N.J.). - New York, NY : Springer New York. - 1940-6029. ; 1672, s. 329-345
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Tidskriftsartikel (refereegranskat)abstract
- Ribonucleotides embedded within DNA render the DNA sensitive to the formation of single-stranded breaks under alkali conditions. Here, we describe a next-generation sequencing method called hydrolytic end sequencing (HydEn-seq) to map ribonucleotides inserted into the genome of Saccharomyce cerevisiae strains deficient in ribonucleotide excision repair. We use this method to map several genomic features in wild-type and replicase variant yeast strains.
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| 5. |
- Watt, Danielle L., et al.
(författare)
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Genome-wide analysis of the specificity and mechanisms of replication infidelity driven by imbalanced dNTP pools
- 2016
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Ingår i: Nucleic Acids Research. - : Oxford University Press (OUP). - 0305-1048 .- 1362-4962. ; 44:4, s. 1669-1680
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The absolute and relative concentrations of the four dNTPs are key determinants of DNA replication fidelity, yet the consequences of altered dNTP pools on replication fidelity have not previously been investigated on a genome-wide scale. Here, we use deep sequencing to determine the types, rates and locations of uncorrected replication errors that accumulate in the nuclear genome of a mismatch repair-deficient diploid yeast strain with elevated dCTP and dTTP concentrations. These imbalanced dNTP pools promote replication errors in specific DNA sequence motifs suggesting increased misinsertion and increased mismatch extension at the expense of proofreading. Interestingly, substitution rates are similar for leading and lagging strand replication, but are higher in regions replicated late in S phase. Remarkably, the rate of single base deletions is preferentially increased in coding sequences and in short rather than long mononucleotides runs. Based on DNA sequence motifs, we propose two distinct mechanisms for generating single base deletions in vivo. Collectively, the results indicate that elevated dCTP and dTTP pools increase mismatch formation and decrease error correction across the nuclear genome, and most strongly increases mutation rates in coding and late replicating sequences.
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| 6. |
- Williams, Jessica S, et al.
(författare)
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Evidence that processing of ribonucleotides in DNA by topoisomerase 1 is leading-strand specific
- 2015
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Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 22:4, s. 291-U35
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Tidskriftsartikel (refereegranskat)abstract
- Ribonucleotides incorporated during DNA replication are removed by RNase H2-dependent ribonucleotide excision repair (RER). In RER-defective yeast, topoisomerase 1 (Top1) incises DNA at unrepaired ribonucleotides, initiating their removal, but this is accompanied by RNA-DNA-damage phenotypes. Here we show that these phenotypes are incurred by a high level of ribonucleotides incorporated by a leading strand-replicase variant, DNA polymerase (Pol) ɛ, but not by orthologous variants of the lagging-strand replicases, Pols α or δ. Moreover, loss of both RNases H1 and H2 is lethal in combination with increased ribonucleotide incorporation by Pol ɛ but not by Pols α or δ. Several explanations for this asymmetry are considered, including the idea that Top1 incision at ribonucleotides relieves torsional stress in the nascent leading strand but not in the nascent lagging strand, in which preexisting nicks prevent the accumulation of superhelical tension.
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| 7. |
- Williams, Jessica S, et al.
(författare)
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Proofreading of ribonucleotides inserted into DNA by yeast DNA polymerase ɛ.
- 2012
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Ingår i: DNA Repair. - : Elsevier BV. - 1568-7864 .- 1568-7856. ; 11:8, s. 649-656
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the ability of the 3' exonuclease activity of Saccharomyces cerevisiae DNA polymerase ɛ (Pol ɛ) to proofread newly inserted ribonucleotides (rNMPs). During DNA synthesis in vitro, Pol ɛ proofreads ribonucleotides with apparent efficiencies that vary from none at some locations to more than 90% at others, with rA and rU being more efficiently proofread than rC and rG. Previous studies show that failure to repair ribonucleotides in the genome of rnh201Δ strains that lack RNase H2 activity elevates the rate of short deletions in tandem repeat sequences. Here we show that this rate is increased by 2-4-fold in pol2-4 rnh201Δ strains that are also defective in Pol ɛ proofreading. In comparison, defective proofreading in these same strains increases the rate of base substitutions by more than 100-fold. Collectively, the results indicate that although proofreading of an 'incorrect' sugar is less efficient than is proofreading of an incorrect base, Pol ɛ does proofread newly inserted rNMPs to enhance genome stability.
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| 8. |
- Williams, Jessica S., et al.
(författare)
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Topoisomerase 1-Mediated Removal of Ribonucleotides from Nascent Leading-Strand DNA
- 2013
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Ingår i: Molecular Cell. - : Cell Press. - 1097-2765 .- 1097-4164. ; 49:5, s. 1010-1015
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Tidskriftsartikel (refereegranskat)abstract
- RNase H2-dependent ribonucleotide excision repair (RER) removes ribonucleotides incorporated during DNA replication. When RER is defective, ribonucleotides in the nascent leading strand of the yeast genome are associated with replication stress and genome instability. Here, we provide evidence that topoisomerase 1 (Top1) initiates an independent form of repair to remove ribonucleotides from genomic DNA. This Top1-dependent process activates the S phase checkpoint. Deleting TOP1 reverses this checkpoint activation and also relieves replication stress and genome instability in RER-defective cells. The results reveal an additional removal pathway for a very common lesion in DNA, and they imply that the "dirty" DNA ends created when Top1 incises ribonucleotides in DNA are responsible for the adverse consequences of ribonucleotides in RNase H2-defective cells.
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| 9. |
- Aksenova, Anna, et al.
(författare)
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Mismatch repair-independent increase in spontaneous mutagenesis in yeast lacking non-essential subunits of DNA polymerase ε
- 2010
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Ingår i: PLoS genetics. - : Public Library of Science. - 1553-7404. ; 6:11, s. e1001209-
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Tidskriftsartikel (refereegranskat)abstract
- Yeast DNA polymerase ε (Pol ε) is a highly accurate and processive enzyme that participates in nuclear DNA replication of the leading strand template. In addition to a large subunit (Pol2) harboring the polymerase and proofreading exonuclease active sites, Pol ε also has one essential subunit (Dpb2) and two smaller, non-essential subunits (Dpb3 and Dpb4) whose functions are not fully understood. To probe the functions of Dpb3 and Dpb4, here we investigate the consequences of their absence on the biochemical properties of Pol ε in vitro and on genome stability in vivo. The fidelity of DNA synthesis in vitro by purified Pol2/Dpb2, i.e. lacking Dpb3 and Dpb4, is comparable to the four-subunit Pol ε holoenzyme. Nonetheless, deletion of DPB3 and DPB4 elevates spontaneous frameshift and base substitution rates in vivo, to the same extent as the loss of Pol ε proofreading activity in a pol2-4 strain. In contrast to pol2-4, however, the dpb3Δdpb4Δ does not lead to a synergistic increase of mutation rates with defects in DNA mismatch repair. The increased mutation rate in dpb3Δdpb4Δ strains is partly dependent on REV3, as well as the proofreading capacity of Pol δ. Finally, biochemical studies demonstrate that the absence of Dpb3 and Dpb4 destabilizes the interaction between Pol ε and the template DNA during processive DNA synthesis and during processive 3' to 5'exonucleolytic degradation of DNA. Collectively, these data suggest a model wherein Dpb3 and Dpb4 do not directly influence replication fidelity per se, but rather contribute to normal replication fork progression. In their absence, a defective replisome may more frequently leave gaps on the leading strand that are eventually filled by Pol ζ or Pol δ, in a post-replication process that generates errors not corrected by the DNA mismatch repair system.
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| 10. |
- Buckland, Robert J, et al.
(författare)
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Increased and Imbalanced dNTP Pools Symmetrically Promote Both Leading and Lagging Strand Replication Infidelity
- 2014
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Ingår i: PLOS Genetics. - : Public Library of Science (PLoS). - 1553-7390 .- 1553-7404. ; 10:12
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Tidskriftsartikel (refereegranskat)abstract
- The fidelity of DNA replication requires an appropriate balance of dNTPs, yet the nascent leading and lagging strands of the nuclear genome are primarily synthesized by replicases that differ in subunit composition, protein partnerships and biochemical properties, including fidelity. These facts pose the question of whether imbalanced dNTP pools differentially influence leading and lagging strand replication fidelity. Here we test this possibility by examining strand-specific replication infidelity driven by a mutation in yeast ribonucleotide reductase, rnr1-Y285A, that leads to elevated dTTP and dCTP concentrations. The results for the CAN1 mutational reporter gene present in opposite orientations in the genome reveal that the rates, and surprisingly even the sequence contexts, of replication errors are remarkably similar for leading and lagging strand synthesis. Moreover, while many mismatches driven by the dNTP pool imbalance are efficiently corrected by mismatch repair, others are repaired less efficiently, especially those in sequence contexts suggesting reduced proofreading due to increased mismatch extension driven by the high dTTP and dCTP concentrations. Thus the two DNA strands of the nuclear genome are at similar risk of mutations resulting from this dNTP pool imbalance, and this risk is not completely suppressed even when both major replication error correction mechanisms are genetically intact.
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