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Mullins EA, Salay LE, Durie CL, Bradley NP, Jackman JE, Ohi MD, Chazin WJ, Eichman BF. A mechanistic model of primer synthesis from catalytic structures of DNA polymerase α-primase. Nat Struct Mol Biol 2024; 31:777-790. [PMID: 38491139 PMCID: PMC11102853 DOI: 10.1038/s41594-024-01227-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2023] [Accepted: 01/12/2024] [Indexed: 03/18/2024]
Abstract
The mechanism by which polymerase α-primase (polα-primase) synthesizes chimeric RNA-DNA primers of defined length and composition, necessary for replication fidelity and genome stability, is unknown. Here, we report cryo-EM structures of Xenopus laevis polα-primase in complex with primed templates representing various stages of DNA synthesis. Our data show how interaction of the primase regulatory subunit with the primer 5' end facilitates handoff of the primer to polα and increases polα processivity, thereby regulating both RNA and DNA composition. The structures detail how flexibility within the heterotetramer enables synthesis across two active sites and provide evidence that termination of DNA synthesis is facilitated by reduction of polα and primase affinities for the varied conformations along the chimeric primer-template duplex. Together, these findings elucidate a critical catalytic step in replication initiation and provide a comprehensive model for primer synthesis by polα-primase.
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Affiliation(s)
- Elwood A Mullins
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN, USA
| | - Lauren E Salay
- Center for Structural Biology, Vanderbilt University, Nashville, TN, USA
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Clarissa L Durie
- Department of Cell and Developmental Biology, University of Michigan School of Medicine, Ann Arbor, MI, USA
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
- Department of Biochemistry, University of Missouri, Columbia, MO, USA
| | - Noah P Bradley
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
- Center for Structural Biology, Vanderbilt University, Nashville, TN, USA
| | - Jane E Jackman
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA
| | - Melanie D Ohi
- Department of Cell and Developmental Biology, University of Michigan School of Medicine, Ann Arbor, MI, USA
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Walter J Chazin
- Center for Structural Biology, Vanderbilt University, Nashville, TN, USA.
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA.
- Department of Chemistry, Vanderbilt University, Nashville, TN, USA.
| | - Brandt F Eichman
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA.
- Center for Structural Biology, Vanderbilt University, Nashville, TN, USA.
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA.
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2
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Mullins EA, Salay LE, Durie CL, Bradley NP, Jackman JE, Ohi MD, Chazin WJ, Eichman BF. A mechanistic model of primer synthesis from catalytic structures of DNA polymerase α-primase. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.16.533013. [PMID: 36993335 PMCID: PMC10055150 DOI: 10.1101/2023.03.16.533013] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
The mechanism by which polymerase α-primase (polα-primase) synthesizes chimeric RNA-DNA primers of defined length and composition, necessary for replication fidelity and genome stability, is unknown. Here, we report cryo-EM structures of polα-primase in complex with primed templates representing various stages of DNA synthesis. Our data show how interaction of the primase regulatory subunit with the primer 5'-end facilitates handoff of the primer to polα and increases polα processivity, thereby regulating both RNA and DNA composition. The structures detail how flexibility within the heterotetramer enables synthesis across two active sites and provide evidence that termination of DNA synthesis is facilitated by reduction of polα and primase affinities for the varied conformations along the chimeric primer/template duplex. Together, these findings elucidate a critical catalytic step in replication initiation and provide a comprehensive model for primer synthesis by polα-primase.
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3
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Dmowski M, Makiela-Dzbenska K, Sharma S, Chabes A, Fijalkowska IJ. Impairment of the non-catalytic subunit Dpb2 of DNA Pol ɛ results in increased involvement of Pol δ on the leading strand. DNA Repair (Amst) 2023; 129:103541. [PMID: 37481989 DOI: 10.1016/j.dnarep.2023.103541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 05/29/2023] [Accepted: 07/05/2023] [Indexed: 07/25/2023]
Abstract
The generally accepted model assumes that leading strand synthesis is performed by Pol ε, while lagging-strand synthesis is catalyzed by Pol δ. Pol ε has been shown to target the leading strand by interacting with the CMG helicase [Cdc45 Mcm2-7 GINS(Psf1-3, Sld5)]. Proper functioning of the CMG-Pol ɛ, the helicase-polymerase complex is essential for its progression and the fidelity of DNA replication. Dpb2p, the essential non-catalytic subunit of Pol ε plays a key role in maintaining the correct architecture of the replisome by acting as a link between Pol ε and the CMG complex. Using a temperature-sensitive dpb2-100 mutant previously isolated in our laboratory, and a genetic system which takes advantage of a distinct mutational signature of the Pol δ-L612M variant which allows detection of the involvement of Pol δ in the replication of particular DNA strands we show that in yeast cells with an impaired Dpb2 subunit, the contribution of Pol δ to the replication of the leading strand is significantly increased.
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Affiliation(s)
- Michal Dmowski
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5A, 02-106 Warsaw, Poland.
| | - Karolina Makiela-Dzbenska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5A, 02-106 Warsaw, Poland
| | - Sushma Sharma
- Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden
| | - Andrei Chabes
- Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden
| | - Iwona J Fijalkowska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5A, 02-106 Warsaw, Poland.
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4
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Yuan Z, Georgescu R, Li H, O'Donnell ME. Molecular choreography of primer synthesis by the eukaryotic Pol α-primase. Nat Commun 2023; 14:3697. [PMID: 37344454 PMCID: PMC10284912 DOI: 10.1038/s41467-023-39441-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 06/14/2023] [Indexed: 06/23/2023] Open
Abstract
The eukaryotic polymerase α (Pol α) synthesizes an RNA-DNA hybrid primer of 20-30 nucleotides. Pol α is composed of Pol1, Pol12, Primase 1 (Pri1), and Pri2. Pol1 and Pri1 contain the DNA polymerase and RNA primase activities, respectively. It has been unclear how Pol α hands over an RNA primer from Pri1 to Pol1 for DNA primer extension, and how the primer length is defined. Here we report the cryo-EM analysis of yeast Pol α in the apo, primer initiation, primer elongation, RNA primer hand-off from Pri1 to Pol1, and DNA extension states, revealing a series of very large movements. We reveal a critical point at which Pol1-core moves to take over the 3'-end of the RNA from Pri1. DNA extension is limited by a spiral motion of Pol1-core. Since both Pri1 and Pol1-core are flexibly attached to a stable platform, primer growth produces stress that limits the primer length.
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Affiliation(s)
- Zuanning Yuan
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA
| | - Roxana Georgescu
- DNA Replication Laboratory and Howard Hughes Medical Institute, Rockefeller University, New York, NY, USA
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA.
| | - Michael E O'Donnell
- DNA Replication Laboratory and Howard Hughes Medical Institute, Rockefeller University, New York, NY, USA.
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5
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Vandenberg BN, Laughery MF, Cordero C, Plummer D, Mitchell D, Kreyenhagen J, Albaqshi F, Brown AJ, Mieczkowski PA, Wyrick JJ, Roberts SA. Contributions of replicative and translesion DNA polymerases to mutagenic bypass of canonical and atypical UV photoproducts. Nat Commun 2023; 14:2576. [PMID: 37142570 PMCID: PMC10160025 DOI: 10.1038/s41467-023-38255-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Accepted: 04/21/2023] [Indexed: 05/06/2023] Open
Abstract
UV exposure induces a mutation signature of C > T substitutions at dipyrimidines in skin cancers. We recently identified additional UV-induced AC > TT and A > T substitutions that could respectively cause BRAF V600K and V600E oncogenic mutations. The mutagenic bypass mechanism past these atypical lesions, however, is unknown. Here, we whole genome sequenced UV-irradiated yeast and used reversion reporters to delineate the roles of replicative and translesion DNA polymerases in mutagenic bypass of UV-lesions. Our data indicates that yeast DNA polymerase eta (pol η) has varied impact on UV-induced mutations: protecting against C > T substitutions, promoting T > C and AC > TT substitutions, and not impacting A > T substitutions. Surprisingly, deletion rad30Δ increased novel UV-induced C > A substitutions at CA dinucleotides. In contrast, DNA polymerases zeta (pol ζ) and epsilon (pol ε) participated in AC > TT and A > T mutations. These results uncover lesion-specific accurate and mutagenic bypass of UV lesions, which likely contribute to key driver mutations in melanoma.
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Affiliation(s)
- Brittany N Vandenberg
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, 99164, USA
| | - Marian F Laughery
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, 99164, USA
| | - Cameron Cordero
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, 99164, USA
| | - Dalton Plummer
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, 99164, USA
| | - Debra Mitchell
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, 99164, USA
| | - Jordan Kreyenhagen
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, 99164, USA
| | - Fatimah Albaqshi
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, 99164, USA
| | - Alexander J Brown
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, 99164, USA
| | - Piotr A Mieczkowski
- Department of Genetics, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - John J Wyrick
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, 99164, USA.
| | - Steven A Roberts
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, 99164, USA.
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6
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Yuan Z, Georgescu R, Li H, O'Donnell ME. Molecular choreography of primer synthesis by the eukaryotic Pol α-primase. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.03.539257. [PMID: 37205351 PMCID: PMC10187153 DOI: 10.1101/2023.05.03.539257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The eukaryotic polymerase α (Pol α) is a dual-function DNA polymerase/primase complex that synthesizes an RNA-DNA hybrid primer of 20-30 nucleotides for DNA replication. Pol α is composed of Pol1, Pol12, Primase 1 (Pri1), and Pri2, with Pol1 and Pri1 containing the DNA polymerase activity and RNA primase activity, respectively, whereas Pol12 and Pri2 serve a structural role. It has been unclear how Pol α hands over an RNA primer made by Pri1 to Pol1 for DNA primer extension, and how the primer length is defined, perhaps due to the difficulty in studying the highly mobile structure. Here we report a comprehensive cryo-EM analysis of the intact 4-subunit yeast Pol α in the apo, primer initiation, primer elongation, RNA primer hand-off from Pri1 to Pol1, and DNA extension states in a 3.5 Å - 5.6 Å resolution range. We found that Pol α is a three-lobed flexible structure. Pri2 functions as a flexible hinge that holds together the catalytic Pol1-core, and the noncatalytic Pol1 CTD that binds to Pol 12 to form a stable platform upon which the other components are organized. In the apo state, Pol1-core is sequestered on the Pol12-Pol1-CTD platform, and Pri1 is mobile perhaps in search of a template. Upon binding a ssDNA template, a large conformation change is induced that enables Pri1 to perform RNA synthesis, and positions Pol1-core to accept the future RNA primed site 50 Å upstream of where Pri1 binds. We reveal in detail the critical point at which Pol1-core takes over the 3'-end of the RNA from Pri1. DNA primer extension appears limited by the spiral motion of Pol1-core while Pri2-CTD stably holds onto the 5' end of the RNA primer. Since both Pri1 and Pol1-core are attached via two linkers to the platform, primer growth will produce stress within this "two-point" attachment that may limit the length of the RNA-DNA hybrid primer. Hence, this study reveals the large and dynamic series of movements that Pol α undergoes to synthesize a primer for DNA replication.
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7
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Njeri C, Pepenella S, Battapadi T, Bambara RA, Balakrishnan L. DNA Polymerase Delta Exhibits Altered Catalytic Properties on Lysine Acetylation. Genes (Basel) 2023; 14:genes14040774. [PMID: 37107532 PMCID: PMC10137900 DOI: 10.3390/genes14040774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 03/20/2023] [Accepted: 03/21/2023] [Indexed: 04/29/2023] Open
Abstract
DNA polymerase delta is the primary polymerase that is involved in undamaged nuclear lagging strand DNA replication. Our mass-spectroscopic analysis has revealed that the human DNA polymerase δ is acetylated on subunits p125, p68, and p12. Using substrates that simulate Okazaki fragment intermediates, we studied alterations in the catalytic properties of acetylated polymerase and compared it to the unmodified form. The current data show that the acetylated form of human pol δ displays a higher polymerization activity compared to the unmodified form of the enzyme. Additionally, acetylation enhances the ability of the polymerase to resolve complex structures such as G-quadruplexes and other secondary structures that might be present on the template strand. More importantly, the ability of pol δ to displace a downstream DNA fragment is enhanced upon acetylation. Our current results suggest that acetylation has a profound effect on the activity of pol δ and supports the hypothesis that acetylation may promote higher-fidelity DNA replication.
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Affiliation(s)
- Catherine Njeri
- Department of Biology, Indiana University Purdue University Indianapolis, Indianapolis, IN 46202, USA
| | - Sharon Pepenella
- Department of Microbiology and Immunology, University of Rochester, School of Medicine and Dentistry, Rochester, NY 14642, USA
| | - Tripthi Battapadi
- Department of Biology, Indiana University Purdue University Indianapolis, Indianapolis, IN 46202, USA
| | - Robert A Bambara
- Department of Microbiology and Immunology, University of Rochester, School of Medicine and Dentistry, Rochester, NY 14642, USA
| | - Lata Balakrishnan
- Department of Biology, Indiana University Purdue University Indianapolis, Indianapolis, IN 46202, USA
- Indiana University Comprehensive Cancer Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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8
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Nir Heyman S, Golan M, Liefshitz B, Kupiec M. A Role for the Interactions between Polδ and PCNA Revealed by Analysis of pol3-01 Yeast Mutants. Genes (Basel) 2023; 14:391. [PMID: 36833317 PMCID: PMC9957047 DOI: 10.3390/genes14020391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 01/30/2023] [Accepted: 01/31/2023] [Indexed: 02/05/2023] Open
Abstract
Several DNA polymerases participate in DNA synthesis during genome replication and DNA repair. PCNA, a homotrimeric ring, acts as a processivity factor for DNA polymerases. PCNA also acts as a "landing pad" for proteins that interact with chromatin and DNA at the moving fork. The interaction between PCNA and polymerase delta (Polδ) is mediated by PIPs (PCNA-interacting peptides), in particular the one on Pol32, a regulatory subunit of Polδ. Here, we demonstrate that pol3-01, an exonuclease mutant of Polδ's catalytic subunit, exhibits a weak interaction with Pol30 compared to the WT DNA polymerase. The weak interaction activates DNA bypass pathways, leading to increased mutagenesis and sister chromatid recombination. Strengthening pol3-01's weak interaction with PCNA suppresses most of the phenotypes. Our results are consistent with a model in which Pol3-01 tends to detach from the chromatin, allowing an easier replacement of Polδ by the trans-lesion synthesis polymerase Zeta (Polz), thus leading to the increased mutagenic phenotype.
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Affiliation(s)
| | | | | | - Martin Kupiec
- The Shmunis School of Biomedicine and Cancer Research, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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9
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Zhou ZX, Follonier C, Lujan SA, Burkholder AB, Zakian VA, Kunkel TA. Pif1 family helicases promote mutation avoidance during DNA replication. Nucleic Acids Res 2022; 50:12844-12855. [PMID: 36533450 PMCID: PMC9825187 DOI: 10.1093/nar/gkac1127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 10/25/2022] [Accepted: 11/12/2022] [Indexed: 12/23/2022] Open
Abstract
Pif1 family 5' → 3' DNA helicases are important for replication fork progression and genome stability. The budding yeast Saccharomyces cerevisiae encodes two Pif1 family helicases, Rrm3 and Pif1, both of which are multi-functional. Here we describe novel functions for Rrm3 in promoting mutation avoidance during DNA replication. We show that loss of RRM3 results in elevated spontaneous mutations made by DNA polymerases Pols ϵ and δ, which are subject to DNA mismatch repair. The absence of RRM3 also causes higher mutagenesis by the fourth B-family DNA polymerase Pol ζ. By genome-wide analysis, we show that the mutational consequences due to loss of RRM3 vary depending on the genomic locus. Rrm3 promotes the accuracy of DNA replication by Pols ϵ and δ across the genome, and it is particularly important for preventing Pol ζ-dependent mutagenesis at tRNA genes. In addition, mutation avoidance by Rrm3 depends on its helicase activity, and Pif1 serves as a backup for Rrm3 in suppressing mutagenesis. We present evidence that the sole human Pif1 family helicase in human cells likely also promotes replication fidelity, suggesting that a role for Pif1 family helicases in mutation avoidance may be evolutionarily conserved, a possible underlying mechanism for its potential tumor-suppressor function.
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Affiliation(s)
- Zhi-Xiong Zhou
- Genome Integrity & Structural Biology Laboratory, Princeton University, Princeton, NJ 08544, USA
| | - Cindy Follonier
- Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Princeton, NJ 08544, USA
| | - Scott A Lujan
- Genome Integrity & Structural Biology Laboratory, Princeton University, Princeton, NJ 08544, USA
| | - Adam B Burkholder
- Integrative Bioinformatics Support Group, NIH/NIEHS, DHHS, Research Triangle Park, NC 27709, USA
| | - Virginia A Zakian
- Department of Molecular Biology, Lewis Thomas Laboratory, Princeton University, Princeton, NJ 08544, USA
| | - Thomas A Kunkel
- Genome Integrity & Structural Biology Laboratory, Princeton University, Princeton, NJ 08544, USA
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10
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Lisova AE, Baranovskiy AG, Morstadt LM, Babayeva ND, Tahirov T. Human DNA polymerase α has a strong mutagenic potential at the initial steps of DNA synthesis. Nucleic Acids Res 2022; 50:12266-12273. [PMID: 36454017 PMCID: PMC9757036 DOI: 10.1093/nar/gkac1101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 09/16/2022] [Accepted: 11/10/2022] [Indexed: 12/05/2022] Open
Abstract
DNA polymerase α (Polα) is essential for DNA replication initiation and makes a notable contribution to genome mutagenesis. The activity and fidelity of Polα during the early steps of DNA replication have not been well studied. Here we show that at the beginning of DNA synthesis, when extending the RNA primer received from primase, Polα is more mutagenic than during the later DNA elongation steps. Kinetic and binding studies revealed substantially higher activity and affinity to the template:primer when Polα interacts with ribonucleotides of a chimeric RNA-DNA primer. Polα activity greatly varies during first six steps of DNA synthesis, and the bias in the rates of correct and incorrect dNTP incorporation leads to impaired fidelity, especially upon the second step of RNA primer extension. Furthermore, increased activity and stability of Polα/template:primer complexes containing RNA-DNA primers result in higher efficiency of mismatch extension.
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Affiliation(s)
| | | | - Lucia M Morstadt
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Nigar D Babayeva
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Tahir H Tahirov
- To whom correspondence should be addressed. Tel: +1 402 559 7608; Fax: +1 402 559 3739;
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Mechanistic investigation of human maturation of Okazaki fragments reveals slow kinetics. Nat Commun 2022; 13:6973. [PMID: 36379932 PMCID: PMC9666535 DOI: 10.1038/s41467-022-34751-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2022] [Accepted: 11/04/2022] [Indexed: 11/16/2022] Open
Abstract
The final steps of lagging strand synthesis induce maturation of Okazaki fragments via removal of the RNA primers and ligation. Iterative cycles between Polymerase δ (Polδ) and Flap endonuclease-1 (FEN1) remove the primer, with an intermediary nick structure generated for each cycle. Here, we show that human Polδ is inefficient in releasing the nick product from FEN1, resulting in non-processive and remarkably slow RNA removal. Ligase 1 (Lig1) can release the nick from FEN1 and actively drive the reaction toward ligation. These mechanisms are coordinated by PCNA, which encircles DNA, and dynamically recruits Polδ, FEN1, and Lig1 to compete for their substrates. Our findings call for investigating additional pathways that may accelerate RNA removal in human cells, such as RNA pre-removal by RNase Hs, which, as demonstrated herein, enhances the maturation rate ~10-fold. They also suggest that FEN1 may attenuate the various activities of Polδ during DNA repair and recombination.
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12
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Zhou ZX, Kunkel TA. Extrinsic proofreading. DNA Repair (Amst) 2022; 117:103369. [PMID: 35850061 PMCID: PMC9561950 DOI: 10.1016/j.dnarep.2022.103369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Revised: 07/01/2022] [Accepted: 07/02/2022] [Indexed: 11/24/2022]
Abstract
The high fidelity of replication of the nuclear DNA genome in eukaryotes involves three processes. Correct rather than incorrect dNTPs are almost always incorporated by the three major replicases, DNA polymerases α, δ and ε. When an incorrect base is occasionally inserted, the latter Pols δ and ε also have a 3 ´ to 5 ´ exonuclease activity that can remove the mismatch to allow correct DNA synthesis to proceed. Lastly, rare mismatches that escape proofreading activity and are present in newly replicated DNA can be removed by DNA mismatch repair. In this review, we consider evidence supporting the hypothesis that the second mechanism, proofreading, can operate in two different ways. Primer terminal mismatches made by either Pol δ or Pol ε can be 'intrinsically' proofread. This mechanism occurs by direct transfer of a misinserted base made at the polymerase active site to the exonuclease active site that is located a short distance away. Intrinsic proofreading allows mismatch excision without intervening enzyme dissociation. Alternatively, considerable evidence suggests that mismatches made by any of the three replicases can also be proofread by 'extrinsic' proofreading by Pol δ. Extrinsic proofreading occurs when a mismatch made by any of the three replicases is initially abandoned, thereby allowing the exonuclease active site of Pol δ to bind directly to and remove the mismatch before replication continues. Here we review the evidence that extrinsic proofreading significantly enhances the fidelity of nuclear DNA replication, and we then briefly consider the implications of this process for evolution and disease.
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Affiliation(s)
- Zhi-Xiong Zhou
- Genome Integrity Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, NC 27709, USA
| | - Thomas A Kunkel
- Genome Integrity Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, NC 27709, USA.
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13
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Adebayo IA, Habib MAH, Sarmiento ME, Acosta A, Yaacob NS, Ismail MN. Proteomic analysis of Malaysian Horseshoe crab (Tachypleus gigas) hemocytes gives insights into its innate immunity host defence system and other biological processes. PLoS One 2022; 17:e0272799. [PMID: 35947629 PMCID: PMC9365167 DOI: 10.1371/journal.pone.0272799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 07/26/2022] [Indexed: 11/18/2022] Open
Abstract
Horseshoe crabs are one of the most studied invertebrates due to their remarkable innate immunity mechanism and biological processes. In this work, the proteins of the lipopolysaccharides (LPS)-stimulated and non-stimulated hemocytes of Malaysian Tachypleus gigas were profiled using LC-MS/MS. A total of 154 proteins were identified in both types of samples. Additionally, seventy-seven proteins were commonly found in both conditions, while 52 and 25 proteins were uniquely found in the LPS-stimulated and non-stimulated hemocytes, respectively. ATP-dependent energy-generating proteins such as actins and BLTX actin-related proteins were detected in both stimulated and non-stimulated T. gigas hemocytes, but more of such proteins were found in the former type. Proteins such as tachylectin-2, coagulogen, c-reactive proteins, histones, hemocyanin, and DNA polymerase, which play key roles in the organism’s innate immunity, were differentially expressed in the hemocytes following LPS challenge. In conclusion, the proteins identified in the hemolymph of T. gigas are vital for the organism’s molecular functions, biological processes, and activation of innate immunity.
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Affiliation(s)
- Ismail Abiola Adebayo
- Faculty of Biomedical Sciences, Department of Microbiology and Immunology, Kampala International University, Ishaka, Bushenyi, Uganda
- Analytical Biochemistry Research Centre, Universiti Sains Malaysia, Bayan Lepas, Pulau Pinang, Malaysia
- Department of Clinical Biology, School of Medicine and Pharmacy, College of Medicine and Health Sciences, University of Rwanda, Kigali, Rwanda
| | - Mohd Afiq Hazlami Habib
- Analytical Biochemistry Research Centre, Universiti Sains Malaysia, Bayan Lepas, Pulau Pinang, Malaysia
| | - Maria E. Sarmiento
- School of Health Sciences, Universiti Sains Malaysia, Kelantan, Malaysia
| | - Armando Acosta
- School of Health Sciences, Universiti Sains Malaysia, Kelantan, Malaysia
| | - Nik Soriani Yaacob
- Department of Chemical Pathology, School of Medical Sciences, Universiti Sains Malaysia (USM), Kelantan, Malaysia
| | - Mohd Nazri Ismail
- Analytical Biochemistry Research Centre, Universiti Sains Malaysia, Bayan Lepas, Pulau Pinang, Malaysia
- Institute for Research in Molecular Medicine, Universiti Sains Malaysia, USM, Pulau Pinang, Malaysia
- * E-mail:
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14
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Wieland J, Buchan S, Sen Gupta S, Mantzouratou A. Genomic instability and the link to infertility: A focus on microsatellites and genomic instability syndromes. Eur J Obstet Gynecol Reprod Biol 2022; 274:229-237. [PMID: 35671666 DOI: 10.1016/j.ejogrb.2022.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 05/25/2022] [Accepted: 06/01/2022] [Indexed: 12/01/2022]
Abstract
Infertility is associated to multiple types of different genomic instabilities and is a genetic feature of genomic instability syndromes. While the mismatch repair machinery contributes to the maintenance of genome integrity, surprisingly its potential role in infertility is overlooked. Defects in mismatch repair mechanisms contribute to microsatellite instability and genomic instability syndromes, due to the inability to repair newly replicated DNA. This article reviews the literature to date to elucidate the contribution of microsatellite instability to genomic instability syndromes and infertility. The key findings presented reveal microsatellite instability is poorly researched in genomic instability syndromes and infertility.
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Affiliation(s)
- Jack Wieland
- Department of Life and Environmental Sciences, Faculty of Science and Technology, Bournemouth University, Poole BH12 5BB, UK.
| | - Sarah Buchan
- Department of Life and Environmental Sciences, Faculty of Science and Technology, Bournemouth University, Poole BH12 5BB, UK.
| | - Sioban Sen Gupta
- Institute for Women's Health, 86-96 Chenies Mews, University College London, London WC1E 6HX, UK.
| | - Anna Mantzouratou
- Department of Life and Environmental Sciences, Faculty of Science and Technology, Bournemouth University, Poole BH12 5BB, UK.
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15
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Efficient discrimination against RNA-containing primers by human DNA polymerase ε. Sci Rep 2022; 12:10163. [PMID: 35715491 PMCID: PMC9205888 DOI: 10.1038/s41598-022-14602-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 06/09/2022] [Indexed: 01/13/2023] Open
Abstract
DNA polymerase ε (Polε) performs bulk synthesis of DNA on the leading strand during genome replication. Polε binds two substrates, a template:primer and dNTP, and catalyzes a covalent attachment of dNMP to the 3' end of the primer. Previous studies have shown that Polε easily inserts and extends ribonucleotides, which may promote mutagenesis and genome instability. In this work, we analyzed the mechanisms of discrimination against RNA-containing primers by human Polε (hPolε), performing binding and kinetic studies at near-physiological salt concentration. Pre-steady-state kinetic studies revealed that hPolεCD extends RNA primers with approximately 3300-fold lower efficiency in comparison to DNA, and addition of one dNMP to the 3' end of an RNA primer increases activity 36-fold. Likewise, addition of one rNMP to the 3' end of a DNA primer reduces activity 38-fold. The binding studies conducted in the presence of 0.15 M NaCl revealed that human hPolεCD has low affinity to DNA (KD of 1.5 µM). Strikingly, a change of salt concentration from 0.1 M to 0.15 M reduces the stability of the hPolεCD/DNA complex by 25-fold. Upon template:primer binding, the incoming dNTP and magnesium ions make hPolε discriminative against RNA and chimeric RNA-DNA primers. In summary, our studies revealed that hPolε discrimination against RNA-containing primers is based on the following factors: incoming dNTP, magnesium ions, a steric gate for the primer 2'OH, and the rigid template:primer binding pocket near the catalytic site. In addition, we showed the importance of conducting functional studies at near-physiological salt concentration.
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16
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Baranovskiy AG, Babayeva ND, Lisova AE, Morstadt LM, Tahirov TH. Structural and functional insight into mismatch extension by human DNA polymerase α. Proc Natl Acad Sci U S A 2022; 119:e2111744119. [PMID: 35467978 PMCID: PMC9169922 DOI: 10.1073/pnas.2111744119] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 03/08/2022] [Indexed: 12/11/2022] Open
Abstract
Human DNA polymerase α (Polα) does not possess proofreading ability and plays an important role in genome replication and mutagenesis. Polα extends the RNA primers generated by primase and provides a springboard for loading other replication factors. Here we provide the structural and functional analysis of the human Polα interaction with a mismatched template:primer. The structure of the human Polα catalytic domain in the complex with an incoming deoxycytidine triphosphate (dCTP) and the template:primer containing a T-C mismatch at the growing primer terminus was solved at a 2.9 Å resolution. It revealed the absence of significant distortions in the active site and in the conformation of the substrates, except the primer 3′-end. The T-C mismatch acquired a planar geometry where both nucleotides moved toward each other by 0.4 Å and 0.7 Å, respectively, and made one hydrogen bond. The binding studies conducted at a physiological salt concentration revealed that Polα has a low affinity to DNA and is not able to discriminate against a mispaired template:primer in the absence of deoxynucleotide triphosphate (dNTP). Strikingly, in the presence of cognate dNTP, Polα showed a more than 10-fold higher selectivity for a correct duplex versus a mismatched one. According to pre-steady-state kinetic studies, human Polα extends the T-C mismatch with a 249-fold lower efficiency due to reduction of the polymerization rate constant by 38-fold and reduced affinity to the incoming nucleotide by 6.6-fold. Thus, a mismatch at the postinsertion site affects all factors important for primer extension: affinity to both substrates and the rate of DNA polymerization.
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Affiliation(s)
- Andrey G. Baranovskiy
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198
| | - Nigar D. Babayeva
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198
| | - Alisa E. Lisova
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198
| | - Lucia M. Morstadt
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198
| | - Tahir H. Tahirov
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198
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17
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Williams JS, Kunkel TA. Ribonucleotide Incorporation by Eukaryotic B-family Replicases and Its Implications for Genome Stability. Annu Rev Biochem 2022; 91:133-155. [PMID: 35287470 DOI: 10.1146/annurev-biochem-032620-110354] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Our current view of how DNA-based genomes are efficiently and accurately replicated continues to evolve as new details emerge on the presence of ribonucleotides in DNA. Ribonucleotides are incorporated during eukaryotic DNA replication at rates that make them the most common noncanonical nucleotide placed into the nuclear genome, they are efficiently repaired, and their removal impacts genome integrity. This review focuses on three aspects of this subject: the incorporation of ribonucleotides into the eukaryotic nuclear genome during replication by B-family DNA replicases, how these ribonucleotides are removed, and the consequences of their presence or removal for genome stability and disease. Expected final online publication date for the Annual Review of Biochemistry, Volume 91 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Jessica S Williams
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, USA;
| | - Thomas A Kunkel
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, USA;
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18
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PrimPol: A Breakthrough among DNA Replication Enzymes and a Potential New Target for Cancer Therapy. Biomolecules 2022; 12:biom12020248. [PMID: 35204749 PMCID: PMC8961649 DOI: 10.3390/biom12020248] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 01/29/2022] [Accepted: 02/02/2022] [Indexed: 02/01/2023] Open
Abstract
DNA replication can encounter blocking obstacles, leading to replication stress and genome instability. There are several mechanisms for evading this blockade. One mechanism consists of repriming ahead of the obstacles, creating a new starting point; in humans, PrimPol is responsible for carrying out this task. PrimPol is a primase that operates in both the nucleus and mitochondria. In contrast with conventional primases, PrimPol is a DNA primase able to initiate DNA synthesis de novo using deoxynucleotides, discriminating against ribonucleotides. In vitro, PrimPol can act as a DNA primase, elongating primers that PrimPol itself sythesizes, or as translesion synthesis (TLS) DNA polymerase, elongating pre-existing primers across lesions. However, the lack of evidence for PrimPol polymerase activity in vivo suggests that PrimPol only acts as a DNA primase. Here, we provide a comprehensive review of human PrimPol covering its biochemical properties and structure, in vivo function and regulation, and the processes that take place to fill the gap-containing lesion that PrimPol leaves behind. Finally, we explore the available data on human PrimPol expression in different tissues in physiological conditions and its role in cancer.
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19
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Dahl JM, Thomas N, Tracy MA, Hearn BL, Perera L, Kennedy SR, Herr AJ, Kunkel TA. Probing the mechanisms of two exonuclease domain mutators of DNA polymerase ϵ. Nucleic Acids Res 2022; 50:962-974. [PMID: 35037018 DOI: 10.1093/nar/gkab1255] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 11/21/2021] [Accepted: 12/08/2021] [Indexed: 11/15/2022] Open
Abstract
We report the properties of two mutations in the exonuclease domain of the Saccharomyces cerevisiae DNA polymerase ϵ. One, pol2-Y473F, increases the mutation rate by about 20-fold, similar to the catalytically dead pol2-D290A/E290A mutant. The other, pol2-N378K, is a stronger mutator. Both retain the ability to excise a nucleotide from double-stranded DNA, but with impaired activity. pol2-Y473F degrades DNA poorly, while pol2-N378K degrades single-stranded DNA at an elevated rate relative to double-stranded DNA. These data suggest that pol2-Y473F reduces the capacity of the enzyme to perform catalysis in the exonuclease active site, while pol2-N378K impairs partitioning to the exonuclease active site. Relative to wild-type Pol ϵ, both variants decrease the dNTP concentration required to elicit a switch between proofreading and polymerization by more than an order of magnitude. While neither mutation appears to alter the sequence specificity of polymerization, the N378K mutation stimulates polymerase activity, increasing the probability of incorporation and extension of a mismatch. Considered together, these data indicate that impairing the primer strand transfer pathway required for proofreading increases the probability of common mutations by Pol ϵ, elucidating the association of homologous mutations in human DNA polymerase ϵ with cancer.
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Affiliation(s)
- Joseph M Dahl
- Genome Integrity Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC 27709, USA
| | - Natalie Thomas
- Genome Integrity Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC 27709, USA
| | - Maxwell A Tracy
- Department of Laboratory Medicine and Pathology, UW Medicine, Seattle, WA 98195, USA
| | - Brady L Hearn
- Department of Laboratory Medicine and Pathology, UW Medicine, Seattle, WA 98195, USA
| | - Lalith Perera
- Genome Integrity Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC 27709, USA
| | - Scott R Kennedy
- Department of Laboratory Medicine and Pathology, UW Medicine, Seattle, WA 98195, USA
| | - Alan J Herr
- Department of Laboratory Medicine and Pathology, UW Medicine, Seattle, WA 98195, USA
| | - Thomas A Kunkel
- Genome Integrity Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC 27709, USA
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20
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Zhou ZX, Lujan SA, Burkholder AB, St. Charles J, Dahl J, Farrell CE, Williams JS, Kunkel TA. How asymmetric DNA replication achieves symmetrical fidelity. Nat Struct Mol Biol 2021; 28:1020-1028. [PMID: 34887558 PMCID: PMC8815454 DOI: 10.1038/s41594-021-00691-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 10/22/2021] [Indexed: 11/09/2022]
Abstract
Accurate DNA replication of an undamaged template depends on polymerase selectivity for matched nucleotides, exonucleolytic proofreading of mismatches, and removal of remaining mismatches via DNA mismatch repair (MMR). DNA polymerases (Pols) δ and ε have 3'-5' exonucleases into which mismatches are partitioned for excision in cis (intrinsic proofreading). Here we provide strong evidence that Pol δ can extrinsically proofread mismatches made by itself and those made by Pol ε, independently of both Pol δ's polymerization activity and MMR. Extrinsic proofreading across the genome is remarkably efficient. We report, with unprecedented accuracy, in vivo contributions of nucleotide selectivity, proofreading, and MMR to the fidelity of DNA replication in Saccharomyces cerevisiae. We show that extrinsic proofreading by Pol δ improves and balances the fidelity of the two DNA strands. Together, we depict a comprehensive picture of how nucleotide selectivity, proofreading, and MMR cooperate to achieve high and symmetrical fidelity on the two strands.
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Affiliation(s)
- Zhi-Xiong Zhou
- Genome Integrity & Structural Biology Laboratory, NIH/NIEHS, DHHS, Research Triangle Park, North Carolina, USA
| | - Scott A. Lujan
- Genome Integrity & Structural Biology Laboratory, NIH/NIEHS, DHHS, Research Triangle Park, North Carolina, USA
| | - Adam B. Burkholder
- Integrative Bioinformatics Support Group, NIH/NIEHS, DHHS, Research Triangle Park, North Carolina, USA
| | - Jordan St. Charles
- Genome Integrity & Structural Biology Laboratory, NIH/NIEHS, DHHS, Research Triangle Park, North Carolina, USA
| | - Joseph Dahl
- Genome Integrity & Structural Biology Laboratory, NIH/NIEHS, DHHS, Research Triangle Park, North Carolina, USA
| | - Corinne E. Farrell
- Genome Integrity & Structural Biology Laboratory, NIH/NIEHS, DHHS, Research Triangle Park, North Carolina, USA
| | - Jessica S. Williams
- Genome Integrity & Structural Biology Laboratory, NIH/NIEHS, DHHS, Research Triangle Park, North Carolina, USA
| | - Thomas A. Kunkel
- Genome Integrity & Structural Biology Laboratory, NIH/NIEHS, DHHS, Research Triangle Park, North Carolina, USA
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21
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PCNA Loaders and Unloaders-One Ring That Rules Them All. Genes (Basel) 2021; 12:genes12111812. [PMID: 34828416 PMCID: PMC8618651 DOI: 10.3390/genes12111812] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 11/15/2021] [Accepted: 11/17/2021] [Indexed: 12/23/2022] Open
Abstract
During each cell duplication, the entirety of the genomic DNA in every cell must be accurately and quickly copied. Given the short time available for the chore, the requirement of many proteins, and the daunting amount of DNA present, DNA replication poses a serious challenge to the cell. A high level of coordination between polymerases and other DNA and chromatin-interacting proteins is vital to complete this task. One of the most important proteins for maintaining such coordination is PCNA. PCNA is a multitasking protein that forms a homotrimeric ring that encircles the DNA. It serves as a processivity factor for DNA polymerases and acts as a landing platform for different proteins interacting with DNA and chromatin. Therefore, PCNA is a signaling hub that influences the rate and accuracy of DNA replication, regulates DNA damage repair, controls chromatin formation during the replication, and the proper segregation of the sister chromatids. With so many essential roles, PCNA recruitment and turnover on the chromatin is of utmost importance. Three different, conserved protein complexes are in charge of loading/unloading PCNA onto DNA. Replication factor C (RFC) is the canonical complex in charge of loading PCNA during the S-phase. The Ctf18 and Elg1 (ATAD5 in mammalian) proteins form complexes similar to RFC, with particular functions in the cell’s nucleus. Here we summarize our current knowledge about the roles of these important factors in yeast and mammals.
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22
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Luo G, Zhang J, Yang M, He H, Huang Z. Selenium atom on phosphate enhances specificity and sensitivity of DNA polymerization and detection. J Mater Chem B 2021; 9:5636-5644. [PMID: 34196647 DOI: 10.1039/d1tb00428j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
DNA polymerization is of high specificity in vivo. However, its specificity is much lower in vitro, which limits advanced applications of DNA polymerization in ultrasensitive nucleic acid detection. Herein, we report a unique mechanism of single selenium-atom modified dNTP (dNTPαSe) to enhance polymerization specificity. We have found that both dNTPαSe (approximately 660 fold) and Se-DNA (approximately 2.8 fold) have lower binding affinity to DNA polymerase than canonical ones, and the Se-DNA duplex has much lower melting-temperature (Tm) than the corresponding canonical DNA duplex. The reduced affinity and Tm can destabilize the substrate-primer-template-enzyme assembly, thereby largely slowing down the mismatch of DNA polymerization and enhancing the amplification specificity and in turn detection sensitivity. Furthermore, the Se-strategy enables us to develop the selenium enhanced specific isothermal amplification (SEA) for nucleic acid detection with high specificity and sensitivity (up to detection of single-digit copies), allowing convenient detection of clinical HPV and COVID-19 viruses in the low-copy number. Clearly, we have discovered the exciting mechanism for enhancing DNA polymerization accuracy, amplification specificity and detection sensitivity by SEA, up to two orders of magnitude higher.
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Affiliation(s)
- Guangcheng Luo
- Key Laboratory of Bio-Resource and Eco-environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan, China. and Department of Clinical Laboratory, Affiliated Hospital of North Sichuan Medical College, Nanchong, Sichuan, China
| | - Jun Zhang
- Key Laboratory of Bio-Resource and Eco-environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan, China.
| | - Mei Yang
- Key Laboratory of Bio-Resource and Eco-environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan, China.
| | - Hongfei He
- Key Laboratory of Bio-Resource and Eco-environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan, China.
| | - Zhen Huang
- Key Laboratory of Bio-Resource and Eco-environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan, China. and SeNA Research Institute and Szostak-CDHT Large Nucleic Acids Institute, Chengdu, Sichuan, China
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23
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Strand discrimination in DNA mismatch repair. DNA Repair (Amst) 2021; 105:103161. [PMID: 34171627 DOI: 10.1016/j.dnarep.2021.103161] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 06/15/2021] [Accepted: 06/16/2021] [Indexed: 11/24/2022]
Abstract
DNA mismatch repair (MMR) corrects non-Watson-Crick basepairs generated by replication errors, recombination intermediates, and some forms of chemical damage to DNA. In MutS and MutL homolog-dependent MMR, damaged bases do not identify the error-containing daughter strand that must be excised and resynthesized. In organisms like Escherichia coli that use methyl-directed MMR, transient undermethylation identifies the daughter strand. For other organisms, growing in vitro and in vivo evidence suggest that strand discrimination is mediated by DNA replication-associated daughter strand nicks that direct asymmetric loading of the replicative clamp (the β-clamp in bacteria and the proliferating cell nuclear antigen, PCNA, in eukaryotes). Structural modeling suggests that replicative clamps mediate strand specificity either through the ability of MutL homologs to recognize the fixed orientation of the daughter strand relative to one face of the replicative clamps or through parental strand-specific diffusion of replicative clamps on DNA, which places the daughter strand in the MutL homolog endonuclease active site. Finally, identification of bacteria that appear to lack strand discrimination mediated by a replicative clamp and a pre-existing nick suggest that other strand discrimination mechanisms exist or that these organisms perform MMR by generating a double-stranded DNA break intermediate, which may be analogous to NucS-mediated MMR.
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24
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Stepchenkova EI, Zhuk AS, Cui J, Tarakhovskaya ER, Barbari SR, Shcherbakova PV, Polev DE, Fedorov R, Poliakov E, Rogozin IB, Lada AG, Pavlov YI. Compensation for the absence of the catalytically active half of DNA polymerase ε in yeast by positively selected mutations in CDC28. Genetics 2021; 218:6222163. [PMID: 33844024 DOI: 10.1093/genetics/iyab060] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 04/02/2021] [Indexed: 11/14/2022] Open
Abstract
Current eukaryotic replication models postulate that leading and lagging DNA strands are replicated predominantly by dedicated DNA polymerases. The catalytic subunit of the leading strand DNA polymerase ε, Pol2, consists of two halves made of two different ancestral B-family DNA polymerases. Counterintuitively, the catalytically active N-terminal half is dispensable, while the inactive C-terminal part is required for viability. Despite extensive studies of yeast Saccharomyces cerevisiae strains lacking the active N-terminal half, it is still unclear how these strains survive and recover. We designed a robust method for constructing mutants with only the C-terminal part of Pol2. Strains without the active polymerase part show severe growth defects, sensitivity to replication inhibitors, chromosomal instability, and elevated spontaneous mutagenesis. Intriguingly, the slow-growing mutant strains rapidly accumulate fast-growing clones. Analysis of genomic DNA sequences of these clones revealed that the adaptation to the loss of the catalytic N-terminal part of Pol2 occurs by a positive selection of mutants with improved growth. Elevated mutation rates help generate sufficient numbers of these variants. Single nucleotide changes in the cell cycle-dependent kinase gene, CDC28, improve the growth of strains lacking the N-terminal part of Pol2, and rescue their sensitivity to replication inhibitors and, in parallel, lower mutation rates. Our study predicts that changes in mammalian homologs of cyclin-dependent kinases may contribute to cellular responses to the leading strand polymerase defects.
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Affiliation(s)
- Elena I Stepchenkova
- Laboratory of Mutagenesis and Genetic Toxicology, Vavilov Institute of General Genetics, Saint-Petersburg Branch, Russian Academy of Sciences, Saint-Petersburg 199034, Russia.,Department of Genetics and Biotechnology, Saint-Petersburg State University, Saint-Petersburg 199034, Russia.,Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Anna S Zhuk
- ITMO University, Saint-Petersburg 191002, Russia
| | - Jian Cui
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Elena R Tarakhovskaya
- Laboratory of Mutagenesis and Genetic Toxicology, Vavilov Institute of General Genetics, Saint-Petersburg Branch, Russian Academy of Sciences, Saint-Petersburg 199034, Russia.,Department of Plant Physiology and Biochemistry, Saint-Petersburg State University, Saint-Petersburg 199034, Russia
| | - Stephanie R Barbari
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Polina V Shcherbakova
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Dmitrii E Polev
- Research Resource Center "Biobank," Research Park, Saint-Petersburg State University, Saint-Petersburg 198504, Russia
| | - Roman Fedorov
- Department of Mathematics, University of Pittsburgh, PA 15213, USA
| | - Eugenia Poliakov
- Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Igor B Rogozin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Artem G Lada
- Department of Microbiology and Molecular Genetics, University of California Davis, Davis, CA 92697, USA
| | - Youri I Pavlov
- Department of Genetics and Biotechnology, Saint-Petersburg State University, Saint-Petersburg 199034, Russia.,Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA.,Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA.,Department of Microbiology and Pathology, University of Nebraska Medical Center, Omaha, NE 68198, USA.,Department of Genetics Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE 68198, USA
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25
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Abstract
The faithful and timely copying of DNA by molecular machines known as replisomes depends on a disparate suite of enzymes and scaffolding factors working together in a highly orchestrated manner. Large, dynamic protein-nucleic acid assemblies that selectively morph between distinct conformations and compositional states underpin this critical cellular process. In this article, we discuss recent progress outlining the physical basis of replisome construction and progression in eukaryotes.
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Affiliation(s)
- Ilan Attali
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA;
| | - Michael R Botchan
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
| | - James M Berger
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA;
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26
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Pavlov YI, Zhuk AS, Stepchenkova EI. DNA Polymerases at the Eukaryotic Replication Fork Thirty Years after: Connection to Cancer. Cancers (Basel) 2020; 12:E3489. [PMID: 33255191 PMCID: PMC7760166 DOI: 10.3390/cancers12123489] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/13/2020] [Accepted: 11/13/2020] [Indexed: 12/13/2022] Open
Abstract
Recent studies on tumor genomes revealed that mutations in genes of replicative DNA polymerases cause a predisposition for cancer by increasing genome instability. The past 10 years have uncovered exciting details about the structure and function of replicative DNA polymerases and the replication fork organization. The principal idea of participation of different polymerases in specific transactions at the fork proposed by Morrison and coauthors 30 years ago and later named "division of labor," remains standing, with an amendment of the broader role of polymerase δ in the replication of both the lagging and leading DNA strands. However, cancer-associated mutations predominantly affect the catalytic subunit of polymerase ε that participates in leading strand DNA synthesis. We analyze how new findings in the DNA replication field help elucidate the polymerase variants' effects on cancer.
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Affiliation(s)
- Youri I. Pavlov
- Eppley Institute for Research in Cancer and Allied Diseases and Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
- Department of Genetics and Biotechnology, Saint-Petersburg State University, 199034 Saint Petersburg, Russia;
| | - Anna S. Zhuk
- International Laboratory of Computer Technologies, ITMO University, 197101 Saint Petersburg, Russia;
| | - Elena I. Stepchenkova
- Department of Genetics and Biotechnology, Saint-Petersburg State University, 199034 Saint Petersburg, Russia;
- Laboratory of Mutagenesis and Genetic Toxicology, Vavilov Institute of General Genetics, Saint-Petersburg Branch, Russian Academy of Sciences, 199034 Saint Petersburg, Russia
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27
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Bulock CR, Xing X, Shcherbakova PV. Mismatch repair and DNA polymerase δ proofreading prevent catastrophic accumulation of leading strand errors in cells expressing a cancer-associated DNA polymerase ϵ variant. Nucleic Acids Res 2020; 48:9124-9134. [PMID: 32756902 PMCID: PMC7498342 DOI: 10.1093/nar/gkaa633] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 07/13/2020] [Accepted: 07/27/2020] [Indexed: 12/15/2022] Open
Abstract
Substitutions in the exonuclease domain of DNA polymerase ϵ cause ultramutated human tumors. Yeast and mouse mimics of the most common variant, P286R, produce mutator effects far exceeding the effect of Polϵ exonuclease deficiency. Yeast Polϵ-P301R has increased DNA polymerase activity, which could underlie its high mutagenicity. We aimed to understand the impact of this increased activity on the strand-specific role of Polϵ in DNA replication and the action of extrinsic correction systems that remove Polϵ errors. Using mutagenesis reporters spanning a well-defined replicon, we show that both exonuclease-deficient Polϵ (Polϵ-exo−) and Polϵ-P301R generate mutations in a strictly strand-specific manner, yet Polϵ-P301R is at least ten times more mutagenic than Polϵ-exo− at each location analyzed. Thus, the cancer variant remains a dedicated leading-strand polymerase with markedly low accuracy. We further show that P301R substitution is lethal in strains lacking Polδ proofreading or mismatch repair (MMR). Heterozygosity for pol2-P301R is compatible with either defect but causes strong synergistic increases in the mutation rate, indicating that Polϵ-P301R errors are corrected by Polδ proofreading and MMR. These data reveal the unexpected ease with which polymerase exchange occurs in vivo, allowing Polδ exonuclease to prevent catastrophic accumulation of Polϵ-P301R-generated errors on the leading strand.
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Affiliation(s)
- Chelsea R Bulock
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Xuanxuan Xing
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Polina V Shcherbakova
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
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Kim TY, Ji ES, Lee JY, Kim JY, Yoo JS, Szasz AM, Dome B, Marko-Varga G, Kwon HJ. DNA Polymerase Alpha Subunit B Is a Binding Protein for Erlotinib Resistance in Non-Small Cell Lung Cancer. Cancers (Basel) 2020; 12:cancers12092613. [PMID: 32933200 PMCID: PMC7564424 DOI: 10.3390/cancers12092613] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Revised: 09/05/2020] [Accepted: 09/10/2020] [Indexed: 12/14/2022] Open
Abstract
Simple Summary Non-small-cell lung carcinoma (NSCLC) covers for almost 85% of all lung cancers and a major contributor to the overall cancer death rate. Erlotinib is used to treat NSCLC via inhibition of epithelial growth factor receptor (EGFR) kinase activity. Despite its high efficacy, recurrence can occur in patients who become resistant to the drug. We performed DARTS LC-MS/MS with SWATH of DIA analysis and identified a novel binding protein of Erlotinib that may underlie NSCLC resistance. Our study indicated that Erlotinib binds POLA2 in addition to EGFR. This was confirmed by DARTS and CETSA results. Importantly, POLA2 expression levels in four NSCLC cell lines were positively correlated with anti-proliferative Erlotinib efficacy (Pearson correlation coefficient, R = 0.9886). These results suggest that POLA2 is a novel complementary target protein of Erlotinib, and could clinically provide validity as a surrogate marker for drug resistance in patients with NSCLC. Abstract Erlotinib inhibits epithelial growth factor receptor (EGFR) kinase activity and is used to treat non-small cell lung cancer (NSCLC). Despite its high efficacy, recurrence can occur in patients who become resistant to the drug. To address the underlying mechanism of Erlotinib resistance, we investigated additional mechanisms related to mode-of-drug-action, by multiple protein-binding interactions, besides EGFR by using drug affinity responsive target stability (DARTS) and liquid chromatography-mass spectrometry (LC-MS/MS) methods with non-labeled Erlotinib. DNA polymerase alpha subunit B (POLA2) was identified as a new Erlotinib binding protein that was validated by the DARTS platform, complemented with cellular thermal shift assays. Genetic knock-down of POLA2 promoted the anti-proliferative effect of the drug in the Erlotinib-resistant cell line H1299 with high POLA2 expression, whereas the overexpression of POLA2 restored anti-proliferative effects in the Erlotinib-sensitive cell line HCC827 with low POLA2 expression. Importantly, POLA2 expression levels in four NSCLC cell lines were positively correlated with anti-proliferative Erlotinib efficacy (Pearson correlation coefficient, R = 0.9886). These results suggest that POLA2 is a novel complementary target protein of Erlotinib, and could clinically provide validity as a surrogate marker for drug resistance in patients with NSCLC.
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Affiliation(s)
- Tae Young Kim
- Chemical Genomics Global Research Lab, Department of Biotechnology, College of Life Science & Biotechnology, Yonsei University, Seoul 120-749, Korea;
| | - Eun Sun Ji
- Korea Basic Science Institute, Ochang 28119, Korea; (E.S.J.); (J.Y.L.); (J.Y.K.); (J.S.Y.)
| | - Ju Yeon Lee
- Korea Basic Science Institute, Ochang 28119, Korea; (E.S.J.); (J.Y.L.); (J.Y.K.); (J.S.Y.)
| | - Jin Young Kim
- Korea Basic Science Institute, Ochang 28119, Korea; (E.S.J.); (J.Y.L.); (J.Y.K.); (J.S.Y.)
| | - Jong Shin Yoo
- Korea Basic Science Institute, Ochang 28119, Korea; (E.S.J.); (J.Y.L.); (J.Y.K.); (J.S.Y.)
| | - A. Marcell Szasz
- Department of Tumor Biology, National Korányi Institute of Pulmonology, 1121 Budapest, Hungary;
- Department of Bioinformatics, Semmelweis University, 1094 Budapest, Hungary
- Division Clinical Protein Science & Imaging, Department of Clinical Sciences (Lund) and Department of Biomedical Engineering, Lund University, SE-221 84 Lund, Sweden;
| | - Balazs Dome
- Department of Thoracic Surgery, National Institute of Oncology and Semmelweis University, 1117 Budapest, Hungary;
- Division of Thoracic Surgery, Department of Surgery, Medical University of Vienna, 1090 Vienna, Austria
| | - Gyorgy Marko-Varga
- Division Clinical Protein Science & Imaging, Department of Clinical Sciences (Lund) and Department of Biomedical Engineering, Lund University, SE-221 84 Lund, Sweden;
| | - Ho Jeong Kwon
- Chemical Genomics Global Research Lab, Department of Biotechnology, College of Life Science & Biotechnology, Yonsei University, Seoul 120-749, Korea;
- Correspondence: ; Tel.: +82-2-2123-5883; Fax: +82-2-362-7265
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29
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Abstract
Polδ and Polε are the two major replicative polymerases in eukaryotes, but their precise roles at the replication fork remain a subject of debate. A bulk of data supports a model where Polε and Polδ synthesize leading and lagging DNA strands, respectively. However, this model has been difficult to reconcile with the fact that mutations in Polδ have much stronger consequences for genome stability than equivalent mutations in Polε. We provide direct evidence for a long-entertained idea that Polδ can proofread errors made by Polε in addition to its own errors, thus, making a more prominent contribution to mutation avoidance. This paper provides an essential advance in the understanding of the mechanism of eukaryotic DNA replication. During eukaryotic replication, DNA polymerases ε (Polε) and δ (Polδ) synthesize the leading and lagging strands, respectively. In a long-known contradiction to this model, defects in the fidelity of Polε have a much weaker impact on mutagenesis than analogous Polδ defects. It has been previously proposed that Polδ contributes more to mutation avoidance because it proofreads mismatches created by Polε in addition to its own errors. However, direct evidence for this model was missing. We show that, in yeast, the mutation rate increases synergistically when a Polε nucleotide selectivity defect is combined with a Polδ proofreading defect, demonstrating extrinsic proofreading of Polε errors by Polδ. In contrast, combining Polδ nucleotide selectivity and Polε proofreading defects produces no synergy, indicating that Polε cannot correct errors made by Polδ. We further show that Polδ can remove errors made by exonuclease-deficient Polε in vitro. These findings illustrate the complexity of the one-strand–one-polymerase model where synthesis appears to be largely divided, but Polδ proofreading operates on both strands.
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30
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Hoitsma NM, Whitaker AM, Schaich MA, Smith MR, Fairlamb MS, Freudenthal BD. Structure and function relationships in mammalian DNA polymerases. Cell Mol Life Sci 2020; 77:35-59. [PMID: 31722068 PMCID: PMC7050493 DOI: 10.1007/s00018-019-03368-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 10/11/2019] [Accepted: 10/31/2019] [Indexed: 12/19/2022]
Abstract
DNA polymerases are vital for the synthesis of new DNA strands. Since the discovery of DNA polymerase I in Escherichia coli, a diverse library of mammalian DNA polymerases involved in DNA replication, DNA repair, antibody generation, and cell checkpoint signaling has emerged. While the unique functions of these DNA polymerases are differentiated by their association with accessory factors and/or the presence of distinctive catalytic domains, atomic resolution structures of DNA polymerases in complex with their DNA substrates have revealed mechanistic subtleties that contribute to their specialization. In this review, the structure and function of all 15 mammalian DNA polymerases from families B, Y, X, and A will be reviewed and discussed with special emphasis on the insights gleaned from recently published atomic resolution structures.
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Affiliation(s)
- Nicole M Hoitsma
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Amy M Whitaker
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Matthew A Schaich
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Mallory R Smith
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Max S Fairlamb
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Bret D Freudenthal
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA.
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31
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Garbacz MA, Cox PB, Sharma S, Lujan SA, Chabes A, Kunkel TA. The absence of the catalytic domains of Saccharomyces cerevisiae DNA polymerase ϵ strongly reduces DNA replication fidelity. Nucleic Acids Res 2019; 47:3986-3995. [PMID: 30698744 DOI: 10.1093/nar/gkz048] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 01/15/2019] [Accepted: 01/23/2019] [Indexed: 11/13/2022] Open
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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Affiliation(s)
- Marta A Garbacz
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, NC 27709, USA
| | - Phillip B Cox
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, NC 27709, USA
| | - Sushma Sharma
- Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden
| | - Scott A Lujan
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, NC 27709, USA
| | - Andrei Chabes
- Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden
| | - Thomas A Kunkel
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, NC 27709, USA
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32
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Opportunities for new studies of nuclear DNA replication enzymology in budding yeast. Curr Genet 2019; 66:299-302. [PMID: 31493018 DOI: 10.1007/s00294-019-01023-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 07/29/2019] [Accepted: 07/30/2019] [Indexed: 12/12/2022]
Abstract
Three major eukaryotic DNA polymerases, Polymerases α, δ, and ε (Pols α, δ, and ε), perform the fundamental process of DNA synthesis at the replication fork both accurately and efficiently. In trying to understand the necessity and flexibility of the polymerase usage, we recently reported that budding yeast cells lacking Pol ε exonuclease and polymerase domains (pol2-16) survive, but have severe growth defects, checkpoint activation, increased level of dNTP pools as well as significant increase in the mutation rates. Herein, we suggest new opportunities to distinguish the roles of Pol ε from those of two other eukaryotic B-family DNA polymerases, Pols δ and ζ.
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33
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Van Esch H, Colnaghi R, Freson K, Starokadomskyy P, Zankl A, Backx L, Abramowicz I, Outwin E, Rohena L, Faulkner C, Leong GM, Newbury-Ecob RA, Challis RC, Õunap K, Jaeken J, Seuntjens E, Devriendt K, Burstein E, Low KJ, O'Driscoll M. Defective DNA Polymerase α-Primase Leads to X-Linked Intellectual Disability Associated with Severe Growth Retardation, Microcephaly, and Hypogonadism. Am J Hum Genet 2019; 104:957-967. [PMID: 31006512 PMCID: PMC6506757 DOI: 10.1016/j.ajhg.2019.03.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Accepted: 03/04/2019] [Indexed: 12/26/2022] Open
Abstract
Replicating the human genome efficiently and accurately is a daunting challenge involving the duplication of upward of three billion base pairs. At the core of the complex machinery that achieves this task are three members of the B family of DNA polymerases: DNA polymerases α, δ, and ε. Collectively these multimeric polymerases ensure DNA replication proceeds at optimal rates approaching 2 × 103 nucleotides/min with an error rate of less than one per million nucleotides polymerized. The majority of DNA replication of undamaged DNA is conducted by DNA polymerases δ and ε. The DNA polymerase α-primase complex performs limited synthesis to initiate the replication process, along with Okazaki-fragment synthesis on the discontinuous lagging strand. An increasing number of human disorders caused by defects in different components of the DNA-replication apparatus have been described to date. These are clinically diverse and involve a wide range of features, including variable combinations of growth delay, immunodeficiency, endocrine insufficiencies, lipodystrophy, and cancer predisposition. Here, by using various complementary approaches, including classical linkage analysis, targeted next-generation sequencing, and whole-exome sequencing, we describe distinct missense and splice-impacting mutations in POLA1 in five unrelated families presenting with an X-linked syndrome involving intellectual disability, proportionate short stature, microcephaly, and hypogonadism. POLA1 encodes the p180 catalytic subunit of DNA polymerase α-primase. A range of replicative impairments could be demonstrated in lymphoblastoid cell lines derived from affected individuals. Our findings describe the presentation of pathogenic mutations in a catalytic component of a B family DNA polymerase member, DNA polymerase α.
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Affiliation(s)
- Hilde Van Esch
- Center for Human Genetics, University Hospitals Leuven, 3000 Leuven, Belgium; Laboratory for the Genetics of Cognition, Department of Human Genetics, Katholieke Universiteit Leuven, 3000 Leuven, Belgium.
| | - Rita Colnaghi
- Genome Damage and Stability Centre, University of Sussex, BN1 9RQ Sussex, UK
| | - Kathleen Freson
- Department of Cardiovascular Sciences, Center for Molecular and Vascular Biology, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Petro Starokadomskyy
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Andreas Zankl
- Department of Clinical Genetics, the Children's Hospital at Westmead, Westmead, NSW 2145, Australia; Children's Hospital Westmead Clinical School, Sydney Medical School, the University of Sydney, Westmead, NSW 2145, Australia; Bone Biology Division and Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Darlinghurst, NSW 2010, Australia
| | - Liesbeth Backx
- Laboratory for the Genetics of Cognition, Department of Human Genetics, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Iga Abramowicz
- Genome Damage and Stability Centre, University of Sussex, BN1 9RQ Sussex, UK
| | - Emily Outwin
- Genome Damage and Stability Centre, University of Sussex, BN1 9RQ Sussex, UK
| | - Luis Rohena
- Division of Genetics, Department of Pediatrics, San Antonio Military Medical Center, San Antonio, TX 78234, USA
| | - Claire Faulkner
- Bristol Genetics Laboratory, Southmead Hospital, BS10 5NB Bristol, UK
| | - Gary M Leong
- Department of Paediatrics, Nepean Hospital, Nepean Clinical School, the University of Sydney, Kingswood, NSW 2747, Australia
| | - Ruth A Newbury-Ecob
- Clinical Genetics, St. Michael's Hospital, University Hospitals NHS Trust, BS2 8HW Bristol, UK
| | - Rachel C Challis
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, EH4 2XU Edinburgh, UK
| | - Katrin Õunap
- Department of Clinical Genetics, United Laboratories, Tartu University Hospital and Institute of Clinical Medicine, University of Tartu, Tartu 50406, Estonia
| | - Jacques Jaeken
- Center for Metabolic Diseases, University Hospitals Leuven, 3000 Leuven, Belgium
| | - Eve Seuntjens
- Developmental Neurobiology, Department of Biology, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Koen Devriendt
- Center for Human Genetics, University Hospitals Leuven, 3000 Leuven, Belgium
| | - Ezra Burstein
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390 Texas, USA
| | - Karen J Low
- Clinical Genetics, St. Michael's Hospital, University Hospitals NHS Trust, BS2 8HW Bristol, UK
| | - Mark O'Driscoll
- Genome Damage and Stability Centre, University of Sussex, BN1 9RQ Sussex, UK.
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34
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DNA Rereplication Is Susceptible to Nucleotide-Level Mutagenesis. Genetics 2019; 212:445-460. [PMID: 31028114 PMCID: PMC6553831 DOI: 10.1534/genetics.119.302194] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 04/15/2019] [Indexed: 12/12/2022] Open
Abstract
The initiation of eukaryotic DNA replication at replication origins is tightly regulated to prevent re-initiation and re-replication within each cell cycle. This regulation is critical for genome stability as re-replication is an extremely potent inducer... The sources of genome instability, a hallmark of cancer, remain incompletely understood. One potential source is DNA rereplication, which arises when the mechanisms that prevent the reinitiation of replication origins within a single cell cycle are compromised. Using the budding yeast Saccharomyces cerevisiae, we previously showed that DNA rereplication is extremely potent at inducing gross chromosomal alterations and that this arises in part because of the susceptibility of rereplication forks to break. Here, we examine the ability of DNA rereplication to induce nucleotide-level mutations. During normal replication these mutations are restricted by three overlapping error-avoidance mechanisms: the nucleotide selectivity of replicative polymerases, their proofreading activity, and mismatch repair. Using lys2InsEA14, a frameshift reporter that is poorly proofread, we show that rereplication induces up to a 30× higher rate of frameshift mutations and that this mutagenesis is due to passage of the rereplication fork, not secondary to rereplication fork breakage. Rereplication can also induce comparable rates of frameshift and base-substitution mutations in a more general mutagenesis reporter CAN1, when the proofreading activity of DNA polymerase ε is inactivated. Finally, we show that the rereplication-induced mutagenesis of both lys2InsEA14 and CAN1 disappears in the absence of mismatch repair. These results suggest that mismatch repair is attenuated during rereplication, although at most sequences DNA polymerase proofreading provides enough error correction to mitigate the mutagenic consequences. Thus, rereplication can facilitate nucleotide-level mutagenesis in addition to inducing gross chromosomal alterations, broadening its potential role in genome instability.
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35
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Foley MC, Couto L, Rauf S, Boyke A. Insights into DNA polymerase δ’s mechanism for accurate DNA replication. J Mol Model 2019; 25:80. [DOI: 10.1007/s00894-019-3957-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 02/05/2019] [Indexed: 11/28/2022]
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36
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Xing X, Kane DP, Bulock CR, Moore EA, Sharma S, Chabes A, Shcherbakova PV. A recurrent cancer-associated substitution in DNA polymerase ε produces a hyperactive enzyme. Nat Commun 2019; 10:374. [PMID: 30670691 PMCID: PMC6343027 DOI: 10.1038/s41467-018-08145-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Accepted: 12/12/2018] [Indexed: 11/17/2022] Open
Abstract
Alterations in the exonuclease domain of DNA polymerase ε (Polε) cause ultramutated tumors. Severe mutator effects of the most common variant, Polε-P286R, modeled in yeast suggested that its pathogenicity involves yet unknown mechanisms beyond simple proofreading deficiency. We show that, despite producing a catastrophic amount of replication errors in vivo, the yeast Polε-P286R analog retains partial exonuclease activity and is more accurate than exonuclease-dead Polε. The major consequence of the arginine substitution is a dramatically increased DNA polymerase activity. This is manifested as a superior ability to copy synthetic and natural templates, extend mismatched primer termini, and bypass secondary DNA structures. We discuss a model wherein the cancer-associated substitution limits access of the 3’-terminus to the exonuclease site and promotes binding at the polymerase site, thus stimulating polymerization. We propose that the ultramutator effect results from increased polymerase activity amplifying the contribution of Polε errors to the genomic mutation rate. Somatic alterations in the exonuclease domain of DNA polymerase ɛ have been linked to the development of highly mutated cancers. Here, the authors report that a major consequence of the most common cancer-associated Polɛ variant is a dramatically increased DNA polymerase activity.
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Affiliation(s)
- Xuanxuan Xing
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, 68198, USA.,Comprehensive Cancer Center, Ohio State University, Columbus, OH, 43210, USA
| | - Daniel P Kane
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, 68198, USA.,Department of Biological and Environmental Sciences, Le Moyne College, Syracuse, NY, 13214, USA
| | - Chelsea R Bulock
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Elizabeth A Moore
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Sushma Sharma
- Department of Medical Biochemistry and Biophysics, Umeå University, 901 87, Umeå, Sweden
| | - Andrei Chabes
- Department of Medical Biochemistry and Biophysics, Umeå University, 901 87, Umeå, Sweden.,Laboratory for Molecular Infection Medicine Sweden, Umeå University, 901 87, Umeå, Sweden
| | - Polina V Shcherbakova
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
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37
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Zheng DQ, Petes TD. Genome Instability Induced by Low Levels of Replicative DNA Polymerases in Yeast. Genes (Basel) 2018; 9:genes9110539. [PMID: 30405078 PMCID: PMC6267110 DOI: 10.3390/genes9110539] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 11/04/2018] [Accepted: 11/05/2018] [Indexed: 11/29/2022] Open
Abstract
Most cells of solid tumors have very high levels of genome instability of several different types, including deletions, duplications, translocations, and aneuploidy. Much of this instability appears induced by DNA replication stress. As a model for understanding this type of instability, we have examined genome instability in yeast strains that have low levels of two of the replicative DNA polymerases: DNA polymerase α and DNA polymerase δ (Polα and Polδ). We show that low levels of either of these DNA polymerases results in greatly elevated levels of mitotic recombination, chromosome rearrangements, and deletions/duplications. The spectrum of events in the two types of strains, however, differs in a variety of ways. For example, a reduced level of Polδ elevates single-base alterations and small deletions considerably more than a reduced level of Polα. In this review, we will summarize the methods used to monitor genome instability in yeast, and how this analysis contributes to understanding the linkage between genome instability and DNA replication stress.
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Affiliation(s)
- Dao-Qiong Zheng
- Ocean College, Zhejiang University, Zhoushan 316021, Zhejiang, China.
| | - Thomas D Petes
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710, USA.
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38
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Kunkel TA. A simple but profound mutation in mouse DNA polymerase ε drives tumorigenesis. J Clin Invest 2018; 128:3754-3756. [PMID: 30124465 DOI: 10.1172/jci123021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Over 40 years ago, Loeb and colleagues proposed that errors in DNA replication produce a mutator phenotype that is involved in generating the multiple mutations required for tumor development. In this issue of the JCI, Li, Castrillon, and colleagues describe a mouse model containing a single base change in the gene encoding replicative DNA polymerase ε (POLE) that mimics the "ultramutator" phenotype recently reported in many human tumors. Their seminal accomplishment validates Loeb's hypothesis and the use of mutational signatures to understand the origins and potentially the treatment of human tumors, and it offers an exciting opportunity to further explore the mechanisms responsible for normal DNA replication fidelity and their perturbations.
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39
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Su KY, Lin LI, Goodman SD, Yen RS, Wu CY, Chang WC, Yang YC, Cheng WC, Fang WH. DNA polymerase I proofreading exonuclease activity is required for endonuclease V repair pathway both in vitro and in vivo. DNA Repair (Amst) 2018. [DOI: 10.1016/j.dnarep.2018.02.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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40
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Baranovskiy AG, Duong VN, Babayeva ND, Zhang Y, Pavlov YI, Anderson KS, Tahirov TH. Activity and fidelity of human DNA polymerase α depend on primer structure. J Biol Chem 2018; 293:6824-6843. [PMID: 29555682 DOI: 10.1074/jbc.ra117.001074] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 03/09/2018] [Indexed: 12/13/2022] Open
Abstract
DNA polymerase α (Polα) plays an important role in genome replication. In a complex with primase, Polα synthesizes chimeric RNA-DNA primers necessary for replication of both chromosomal DNA strands. During RNA primer extension with deoxyribonucleotides, Polα needs to use double-stranded helical substrates having different structures. Here, we provide a detailed structure-function analysis of human Polα's interaction with dNTPs and DNA templates primed with RNA, chimeric RNA-DNA, or DNA. We report the crystal structures of two ternary complexes of the Polα catalytic domain containing dCTP, a DNA template, and either a DNA or an RNA primer. Unexpectedly, in the ternary complex with a DNA:DNA duplex and dCTP, the "fingers" subdomain of Polα is in the open conformation. Polα induces conformational changes in the DNA and hybrid duplexes to produce the universal double helix form. Pre-steady-state kinetic studies indicated for both duplex types that chemical catalysis rather than product release is the rate-limiting step. Moreover, human Polα extended DNA primers with higher efficiency but lower processivity than it did with RNA and chimeric primers. Polα has a substantial propensity to make errors during DNA synthesis, and we observed that its fidelity depends on the type of sugar at the primer 3'-end. A detailed structural comparison of Polα with other replicative DNA polymerases disclosed common features and some differences, which may reflect the specialization of each polymerase in genome replication.
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Affiliation(s)
- Andrey G Baranovskiy
- From the Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, and
| | - Vincent N Duong
- the Departments of Pharmacology and Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06510
| | - Nigar D Babayeva
- From the Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, and
| | - Yinbo Zhang
- From the Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, and
| | - Youri I Pavlov
- From the Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, and.,the Departments of Biochemistry and Molecular Biology, Pathology and Microbiology, and Genetics and Anatomy, University of Nebraska Medical Center, Omaha, Nebraska 68198 and
| | - Karen S Anderson
- the Departments of Pharmacology and Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06510
| | - Tahir H Tahirov
- From the Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, and
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41
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Fidelity of DNA replication-a matter of proofreading. Curr Genet 2018; 64:985-996. [PMID: 29500597 PMCID: PMC6153641 DOI: 10.1007/s00294-018-0820-1] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 02/27/2018] [Accepted: 02/28/2018] [Indexed: 01/29/2023]
Abstract
DNA that is transmitted to daughter cells must be accurately duplicated to maintain genetic integrity and to promote genetic continuity. A major function of replicative DNA polymerases is to replicate DNA with the very high accuracy. The fidelity of DNA replication relies on nucleotide selectivity of replicative DNA polymerase, exonucleolytic proofreading, and postreplicative DNA mismatch repair (MMR). Proofreading activity that assists most of the replicative polymerases is responsible for removal of incorrectly incorporated nucleotides from the primer terminus before further primer extension. It is estimated that proofreading improves the fidelity by a 2–3 orders of magnitude. The primer with the incorrect terminal nucleotide has to be moved to exonuclease active site, and after removal of the wrong nucleotide must be transferred back to polymerase active site. The mechanism that allows the transfer of the primer between pol and exo site is not well understood. While defects in MMR are well known to be linked with increased cancer incidence only recently, the replicative polymerases that have alterations in the exonuclease domain have been associated with some sporadic and hereditary human cancers. In this review, we would like to emphasize the importance of proofreading (3′-5′ exonuclease activity) in the fidelity of DNA replication and to highlight what is known about switching from polymerase to exonuclease active site.
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42
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Family A and B DNA Polymerases in Cancer: Opportunities for Therapeutic Interventions. BIOLOGY 2018; 7:biology7010005. [PMID: 29301327 PMCID: PMC5872031 DOI: 10.3390/biology7010005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 12/14/2017] [Accepted: 12/29/2017] [Indexed: 02/07/2023]
Abstract
DNA polymerases are essential for genome replication, DNA repair and translesion DNA synthesis (TLS). Broadly, these enzymes belong to two groups: replicative and non-replicative DNA polymerases. A considerable body of data suggests that both groups of DNA polymerases are associated with cancer. Many mutations in cancer cells are either the result of error-prone DNA synthesis by non-replicative polymerases, or the inability of replicative DNA polymerases to proofread mismatched nucleotides due to mutations in 3'-5' exonuclease activity. Moreover, non-replicative, TLS-capable DNA polymerases can negatively impact cancer treatment by synthesizing DNA past lesions generated from treatments such as cisplatin, oxaliplatin, etoposide, bleomycin, and radiotherapy. Hence, the inhibition of DNA polymerases in tumor cells has the potential to enhance treatment outcomes. Here, we review the association of DNA polymerases in cancer from the A and B families, which participate in lesion bypass, and conduct gene replication. We also discuss possible therapeutic interventions that could be used to maneuver the role of these enzymes in tumorigenesis.
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43
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Schroeder JW, Yeesin P, Simmons LA, Wang JD. Sources of spontaneous mutagenesis in bacteria. Crit Rev Biochem Mol Biol 2017; 53:29-48. [PMID: 29108429 DOI: 10.1080/10409238.2017.1394262] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Mutations in an organism's genome can arise spontaneously, that is, in the absence of exogenous stress and prior to selection. Mutations are often neutral or deleterious to individual fitness but can also provide genetic diversity driving evolution. Mutagenesis in bacteria contributes to the already serious and growing problem of antibiotic resistance. However, the negative impacts of spontaneous mutagenesis on human health are not limited to bacterial antibiotic resistance. Spontaneous mutations also underlie tumorigenesis and evolution of drug resistance. To better understand the causes of genetic change and how they may be manipulated in order to curb antibiotic resistance or the development of cancer, we must acquire a mechanistic understanding of the major sources of mutagenesis. Bacterial systems are particularly well-suited to studying mutagenesis because of their fast growth rate and the panoply of available experimental tools, but efforts to understand mutagenic mechanisms can be complicated by the experimental system employed. Here, we review our current understanding of mutagenic mechanisms in bacteria and describe the methods used to study mutagenesis in bacterial systems.
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Affiliation(s)
- Jeremy W Schroeder
- a Department of Bacteriology , University of Wisconsin - Madison , Madison , WI , USA
| | - Ponlkrit Yeesin
- a Department of Bacteriology , University of Wisconsin - Madison , Madison , WI , USA
| | - Lyle A Simmons
- b Department of Molecular, Cellular, and Developmental Biology , University of Michigan , Ann Arbor , MI , USA
| | - Jue D Wang
- a Department of Bacteriology , University of Wisconsin - Madison , Madison , WI , USA
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44
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Liu D, Frederiksen JH, Liberti SE, Lützen A, Keijzers G, Pena-Diaz J, Rasmussen LJ. Human DNA polymerase delta double-mutant D316A;E318A interferes with DNA mismatch repair in vitro. Nucleic Acids Res 2017; 45:9427-9440. [PMID: 28934474 PMCID: PMC5766205 DOI: 10.1093/nar/gkx611] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2016] [Accepted: 07/05/2017] [Indexed: 12/11/2022] Open
Abstract
DNA mismatch repair (MMR) is a highly-conserved DNA repair mechanism, whose primary role is to remove DNA replication errors preventing them from manifesting as mutations, thereby increasing the overall genome stability. Defects in MMR are associated with increased cancer risk in humans and other organisms. Here, we characterize the interaction between MMR and a proofreading-deficient allele of the human replicative DNA polymerase delta, PolδD316A;E318A, which has a higher capacity for strand displacement DNA synthesis than wild type Polδ. Human cell lines overexpressing PolδD316A;E318A display a mild mutator phenotype, while nuclear extracts of these cells exhibit reduced MMR activity in vitro, and these defects are complemented by overexpression or addition of exogenous human Exonuclease 1 (EXO1). By contrast, another proofreading-deficient mutant, PolδD515V, which has a weaker strand displacement activity, does not decrease the MMR activity as significantly as PolδD316A;E318A. In addition, PolδD515V does not increase the mutation frequency in MMR-proficient cells. Based on our findings, we propose that the proofreading activity restricts the strand displacement activity of Polδ in MMR. This contributes to maintain the nicks required for EXO1 entry, and in this manner ensures the dominance of the EXO1-dependent MMR pathway.
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Affiliation(s)
- Dekang Liu
- Center for Healthy Aging, University of Copenhagen, Denmark.,Department of Cellular and Molecular Medicine, University of Copenhagen, Denmark
| | - Jane H Frederiksen
- Center for Healthy Aging, University of Copenhagen, Denmark.,Department of Cellular and Molecular Medicine, University of Copenhagen, Denmark
| | - Sascha E Liberti
- Center for Healthy Aging, University of Copenhagen, Denmark.,Department of Cellular and Molecular Medicine, University of Copenhagen, Denmark
| | - Anne Lützen
- Department of Science, Systems and Models, Roskilde University, Denmark
| | - Guido Keijzers
- Center for Healthy Aging, University of Copenhagen, Denmark.,Department of Cellular and Molecular Medicine, University of Copenhagen, Denmark
| | - Javier Pena-Diaz
- Center for Healthy Aging, University of Copenhagen, Denmark.,Department of Cellular and Molecular Medicine, University of Copenhagen, Denmark
| | - Lene Juel Rasmussen
- Center for Healthy Aging, University of Copenhagen, Denmark.,Department of Cellular and Molecular Medicine, University of Copenhagen, Denmark
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45
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Paschalis V, Le Chatelier E, Green M, Nouri H, Képès F, Soultanas P, Janniere L. Interactions of the Bacillus subtilis DnaE polymerase with replisomal proteins modulate its activity and fidelity. Open Biol 2017; 7:170146. [PMID: 28878042 PMCID: PMC5627055 DOI: 10.1098/rsob.170146] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 08/01/2017] [Indexed: 01/09/2023] Open
Abstract
During Bacillus subtilis replication two replicative polymerases function at the replisome to collectively carry out genome replication. In a reconstituted in vitro replication assay, PolC is the main polymerase while the lagging strand DnaE polymerase briefly extends RNA primers synthesized by the primase DnaG prior to handing-off DNA synthesis to PolC. Here, we show in vivo that (i) the polymerase activity of DnaE is essential for both the initiation and elongation stages of DNA replication, (ii) its error rate varies inversely with PolC concentration, and (iii) its misincorporations are corrected by the mismatch repair system post-replication. We also found that the error rates in cells encoding mutator forms of both PolC and DnaE are significantly higher (up to 15-fold) than in PolC mutants. In vitro, we showed that (i) the polymerase activity of DnaE is considerably stimulated by DnaN, SSB and PolC, (ii) its error-prone activity is strongly inhibited by DnaN, and (iii) its errors are proofread by the 3' > 5' exonuclease activity of PolC in a stable template-DnaE-PolC complex. Collectively our data show that protein-protein interactions within the replisome modulate the activity and fidelity of DnaE, and confirm the prominent role of DnaE during B. subtilis replication.
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Affiliation(s)
- Vasileios Paschalis
- Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Emmanuelle Le Chatelier
- Institut National de la Recherche Agronomique, Génétique Microbienne, 78350 Jouy-en-Josas, France
| | - Matthew Green
- Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Hamid Nouri
- iSSB, Genopole, CNRS, Univ EVRY, Université Paris-Saclay, Génopole Campus 1, Genavenir 6, 5 rue Henri Desbruères, 91030 Evry, France
| | - François Képès
- iSSB, Genopole, CNRS, Univ EVRY, Université Paris-Saclay, Génopole Campus 1, Genavenir 6, 5 rue Henri Desbruères, 91030 Evry, France
| | - Panos Soultanas
- Centre for Biomolecular Sciences, School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Laurent Janniere
- iSSB, Genopole, CNRS, Univ EVRY, Université Paris-Saclay, Génopole Campus 1, Genavenir 6, 5 rue Henri Desbruères, 91030 Evry, France
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46
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Abstract
The fidelity of DNA replication is determined by many factors, here simplified as the contribution of the DNA polymerase (nucleotide selectivity and proofreading), mismatch repair, a balanced supply of nucleotides, and the condition of the DNA template (both in terms of sequence context and the presence of DNA lesions). This review discusses the contribution and interplay between these factors to the overall fidelity of DNA replication.
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Affiliation(s)
- Rais A Ganai
- Department of Medical Biochemistry and Biophysics, Umeå University, SE 901 87 Umeå, Sweden; Howard Hughes Medical Institute, Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, NY 10016, USA
| | - Erik Johansson
- Department of Medical Biochemistry and Biophysics, Umeå University, SE 901 87 Umeå, Sweden.
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47
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Hedglin M, Benkovic SJ. Eukaryotic Translesion DNA Synthesis on the Leading and Lagging Strands: Unique Detours around the Same Obstacle. Chem Rev 2017; 117:7857-7877. [PMID: 28497687 PMCID: PMC5662946 DOI: 10.1021/acs.chemrev.7b00046] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
During S-phase, minor DNA damage may be overcome by DNA damage tolerance (DDT) pathways that bypass such obstacles, postponing repair of the offending damage to complete the cell cycle and maintain cell survival. In translesion DNA synthesis (TLS), specialized DNA polymerases replicate the damaged DNA, allowing stringent DNA synthesis by a replicative polymerase to resume beyond the offending damage. Dysregulation of this DDT pathway in human cells leads to increased mutation rates that may contribute to the onset of cancer. Furthermore, TLS affords human cancer cells the ability to counteract chemotherapeutic agents that elicit cell death by damaging DNA in actively replicating cells. Currently, it is unclear how this critical pathway unfolds, in particular, where and when TLS occurs on each template strand. Given the semidiscontinuous nature of DNA replication, it is likely that TLS on the leading and lagging strand templates is unique for each strand. Since the discovery of DDT in the late 1960s, most studies on TLS in eukaryotes have focused on DNA lesions resulting from ultraviolet (UV) radiation exposure. In this review, we revisit these and other related studies to dissect the step-by-step intricacies of this complex process, provide our current understanding of TLS on leading and lagging strand templates, and propose testable hypotheses to gain further insights.
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Affiliation(s)
- Mark Hedglin
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, U.S.A
| | - Stephen J. Benkovic
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, U.S.A
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48
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Abstract
The accurate and complete replication of genomic DNA is essential for all life. In eukaryotic cells, the assembly of the multi-enzyme replisomes that perform replication is divided into stages that occur at distinct phases of the cell cycle. Replicative DNA helicases are loaded around origins of DNA replication exclusively during G1 phase. The loaded helicases are then activated during S phase and associate with the replicative DNA polymerases and other accessory proteins. The function of the resulting replisomes is monitored by checkpoint proteins that protect arrested replisomes and inhibit new initiation when replication is inhibited. The replisome also coordinates nucleosome disassembly, assembly, and the establishment of sister chromatid cohesion. Finally, when two replisomes converge they are disassembled. Studies in Saccharomyces cerevisiae have led the way in our understanding of these processes. Here, we review our increasingly molecular understanding of these events and their regulation.
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49
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Andrianova MA, Bazykin GA, Nikolaev SI, Seplyarskiy VB. Human mismatch repair system balances mutation rates between strands by removing more mismatches from the lagging strand. Genome Res 2017; 27:1336-1343. [PMID: 28512192 PMCID: PMC5538550 DOI: 10.1101/gr.219915.116] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 05/09/2017] [Indexed: 12/13/2022]
Abstract
Mismatch repair (MMR) is one of the main systems maintaining fidelity of replication. Differences in correction of errors produced during replication of the leading and the lagging DNA strands were reported in yeast and in human cancers, but the causes of these differences remain unclear. Here, we analyze data on human cancers with somatic mutations in two of the major DNA polymerases, delta and epsilon, that replicate the genome. We show that these cancers demonstrate a substantial asymmetry of the mutations between the leading and the lagging strands. The direction of this asymmetry is the opposite between cancers with mutated polymerases delta and epsilon, consistent with the role of these polymerases in replication of the lagging and the leading strands in human cells, respectively. Moreover, the direction of strand asymmetry observed in cancers with mutated polymerase delta is similar to that observed in MMR-deficient cancers. Together, these data indicate that polymerase delta (possibly together with polymerase alpha) contributes more mismatches during replication than its leading-strand counterpart, polymerase epsilon; that most of these mismatches are repaired by the MMR system; and that MMR repairs about three times more mismatches produced in cells during lagging strand replication compared with the leading strand.
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Affiliation(s)
- Maria A Andrianova
- Institute for Information Transmission Problems of the Russian Academy of Sciences (Kharkevich Institute), Moscow 127994, Russia.,Lomonosov Moscow State University, Moscow 119234, Russia
| | - Georgii A Bazykin
- Institute for Information Transmission Problems of the Russian Academy of Sciences (Kharkevich Institute), Moscow 127994, Russia.,Skolkovo Institute of Science and Technology, Skolkovo 143026, Russia
| | - Sergey I Nikolaev
- Department of Genetic Medicine and Development, University of Geneva Medical School, 1211 Geneva, Switzerland.,Institute of Genetics and Genomics in Geneva, 1211 Geneva, Switzerland
| | - Vladimir B Seplyarskiy
- Institute for Information Transmission Problems of the Russian Academy of Sciences (Kharkevich Institute), Moscow 127994, Russia.,Division of Genetics, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA
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50
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Risks at the DNA Replication Fork: Effects upon Carcinogenesis and Tumor Heterogeneity. Genes (Basel) 2017; 8:genes8010046. [PMID: 28117753 PMCID: PMC5295039 DOI: 10.3390/genes8010046] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 01/09/2017] [Accepted: 01/17/2017] [Indexed: 12/27/2022] Open
Abstract
The ability of all organisms to copy their genetic information via DNA replication is a prerequisite for cell division and a biological imperative of life. In multicellular organisms, however, mutations arising from DNA replication errors in the germline and somatic cells are the basis of genetic diseases and cancer, respectively. Within human tumors, replication errors additionally contribute to mutator phenotypes and tumor heterogeneity, which are major confounding factors for cancer therapeutics. Successful DNA replication involves the coordination of many large-scale, complex cellular processes. In this review, we focus on the roles that defects in enzymes that normally act at the replication fork and dysregulation of enzymes that inappropriately damage single-stranded DNA at the fork play in causing mutations that contribute to carcinogenesis. We focus on tumor data and experimental evidence that error-prone variants of replicative polymerases promote carcinogenesis and on research indicating that the primary target mutated by APOBEC (apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like) cytidine deaminases is ssDNA present at the replication fork. Furthermore, we discuss evidence from model systems that indicate replication stress and other cancer-associated metabolic changes may modulate mutagenic enzymatic activities at the replication fork.
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