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Sikand A, Jaszczur M, Bloom LB, Woodgate R, Cox MM, Goodman MF. The SOS Error-Prone DNA Polymerase V Mutasome and β-Sliding Clamp Acting in Concert on Undamaged DNA and during Translesion Synthesis. Cells 2021; 10:cells10051083. [PMID: 34062858 PMCID: PMC8147279 DOI: 10.3390/cells10051083] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 04/27/2021] [Accepted: 04/28/2021] [Indexed: 11/16/2022] Open
Abstract
In the mid 1970s, Miroslav Radman and Evelyn Witkin proposed that Escherichia coli must encode a specialized error-prone DNA polymerase (pol) to account for the 100-fold increase in mutations accompanying induction of the SOS regulon. By the late 1980s, genetic studies showed that SOS mutagenesis required the presence of two “UV mutagenesis” genes, umuC and umuD, along with recA. Guided by the genetics, decades of biochemical studies have defined the predicted error-prone DNA polymerase as an activated complex of these three gene products, assembled as a mutasome, pol V Mut = UmuD’2C-RecA-ATP. Here, we explore the role of the β-sliding processivity clamp on the efficiency of pol V Mut-catalyzed DNA synthesis on undamaged DNA and during translesion DNA synthesis (TLS). Primer elongation efficiencies and TLS were strongly enhanced in the presence of β. The results suggest that β may have two stabilizing roles: its canonical role in tethering the pol at a primer-3’-terminus, and a possible second role in inhibiting pol V Mut’s ATPase to reduce the rate of mutasome-DNA dissociation. The identification of umuC, umuD, and recA homologs in numerous strains of pathogenic bacteria and plasmids will ensure the long and productive continuation of the genetic and biochemical journey initiated by Radman and Witkin.
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Affiliation(s)
- Adhirath Sikand
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA;
| | - Malgorzata Jaszczur
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA;
| | - Linda B. Bloom
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32611, USA;
| | - Roger Woodgate
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20814, USA;
| | - Michael M. Cox
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA;
| | - Myron F. Goodman
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA;
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA;
- Correspondence:
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2
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Vaisman A, Woodgate R. Mysterious and fascinating: DNA polymerase ɩ remains enigmatic 20 years after its discovery. DNA Repair (Amst) 2020; 93:102914. [PMID: 33087280 DOI: 10.1016/j.dnarep.2020.102914] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
With the publication of the first paper describing the biochemical properties of DNA polymerase iota (polɩ), the question immediately arose as to why cells harbor such a low-fidelity enzyme which often violates the Watson-Crick base pairing rules? Yet 20 years after its discovery, the cellular function of polɩ remains unknown. Here, we provide a graphical review of the unique biochemical properties of polɩ and speculate about the cellular pathways in which enigmatic polɩ may participate.
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Affiliation(s)
- Alexandra Vaisman
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA
| | - Roger Woodgate
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA.
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3
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Walsh E, Henrikus SS, Vaisman A, Makiela-Dzbenska K, Armstrong TJ, Łazowski K, McDonald JP, Goodman MF, van Oijen AM, Jonczyk P, Fijalkowska IJ, Robinson A, Woodgate R. Role of RNase H enzymes in maintaining genome stability in Escherichia coli expressing a steric-gate mutant of pol V ICE391. DNA Repair (Amst) 2019; 84:102685. [PMID: 31543434 DOI: 10.1016/j.dnarep.2019.102685] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 07/31/2019] [Accepted: 08/03/2019] [Indexed: 11/18/2022]
Abstract
pol VICE391 (RumA'2B) is a low-fidelity polymerase that promotes considerably higher levels of spontaneous "SOS-induced" mutagenesis than the related E. coli pol V (UmuD'2C). The molecular basis for the enhanced mutagenesis was previously unknown. Using single molecule fluorescence microscopy to visualize pol V enzymes, we discovered that the elevated levels of mutagenesis are likely due, in part, to prolonged binding of RumB to genomic DNA leading to increased levels of DNA synthesis compared to UmuC. We have generated a steric gate pol VICE391 variant (pol VICE391_Y13A) that readily misincorporates ribonucleotides into the E. coli genome and have used the enzyme to investigate the molecular mechanisms of Ribonucleotide Excision Repair (RER) under conditions of increased ribonucleotide-induced stress. To do so, we compared the extent of spontaneous mutagenesis promoted by pol V and pol VICE391 to that of their respective steric gate variants. Levels of mutagenesis promoted by the steric gate variants that are lower than that of the wild-type enzyme are indicative of active RER that removes misincorporated ribonucleotides, but also misincorporated deoxyribonucleotides from the genome. Using such an approach, we confirmed that RNase HII plays a pivotal role in RER. In the absence of RNase HII, Nucleotide Excision Repair (NER) proteins help remove misincorporated ribonucleotides. However, significant RER occurs in the absence of RNase HII and NER. Most of the RNase HII and NER-independent RER occurs on the lagging strand during genome duplication. We suggest that this is most likely due to efficient RNase HI-dependent RER which recognizes the polyribonucleotide tracts generated by pol VICE391_Y13A. These activities are critical for the maintenance of genomic integrity when RNase HII is overwhelmed, or inactivated, as ΔrnhB or ΔrnhB ΔuvrA strains expressing pol VICE391_Y13A exhibit genome and plasmid instability in the absence of RNase HI.
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Affiliation(s)
- Erin Walsh
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA
| | - Sarah S Henrikus
- Molecular Horizons Institute and School of Chemistry and Biomolecular Science, University of Wollongong, Australia; Illawarra Health and Medical Research Institute, Wollongong, Australia
| | - Alexandra Vaisman
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA
| | | | - Thomas J Armstrong
- Molecular Horizons Institute and School of Chemistry and Biomolecular Science, University of Wollongong, Australia; Illawarra Health and Medical Research Institute, Wollongong, Australia
| | - Krystian Łazowski
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - John P McDonald
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA
| | - Myron F Goodman
- Departments of Biological Sciences and Chemistry, University of Southern California, Los Angeles, CA 90089-2910 USA
| | - Antoine M van Oijen
- Molecular Horizons Institute and School of Chemistry and Biomolecular Science, University of Wollongong, Australia; Illawarra Health and Medical Research Institute, Wollongong, Australia
| | - Piotr Jonczyk
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - Iwona J Fijalkowska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - Andrew Robinson
- Molecular Horizons Institute and School of Chemistry and Biomolecular Science, University of Wollongong, Australia; Illawarra Health and Medical Research Institute, Wollongong, Australia
| | - Roger Woodgate
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA.
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4
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Ikehata H. Mechanistic considerations on the wavelength-dependent variations of UVR genotoxicity and mutagenesis in skin: the discrimination of UVA-signature from UV-signature mutation. Photochem Photobiol Sci 2018; 17:1861-1871. [PMID: 29850669 DOI: 10.1039/c7pp00360a] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Ultraviolet radiation (UVR) predominantly induces UV-signature mutations, C → T and CC → TT base substitutions at dipyrimidine sites, in the cellular and skin genome. I observed in our in vivo mutation studies of mouse skin that these UVR-specific mutations show a wavelength-dependent variation in their sequence-context preference. The C → T mutation occurs most frequently in the 5'-TCG-3' sequence regardless of the UVR wavelength, but is recovered more preferentially there as the wavelength increases, resulting in prominent occurrences exclusively in the TCG sequence in the UVA wavelength range, which I will designate as a "UVA signature" in this review. The preference of the UVB-induced C → T mutation for the sequence contexts shows a mixed pattern of UVC- and UVA-induced mutations, and a similar pattern is also observed for natural sunlight, in which UVB is the most genotoxic component. In addition, the CC → TT mutation hardly occurs at UVA1 wavelengths, although it is detected rarely but constantly in the UVC and UVB ranges. This wavelength-dependent variation in the sequence-context preference of the UVR-specific mutations could be explained by two different photochemical mechanisms of cyclobutane pyrimidine dimer (CPD) formation. The UV-signature mutations observed in the UVC and UVB ranges are known to be caused mainly by CPDs produced through the conventional singlet/triplet excitation of pyrimidine bases after the direct absorption of the UVC/UVB photon energy in those bases. On the other hand, a novel photochemical mechanism through the direct absorption of the UVR energy to double-stranded DNA, which is called "collective excitation", has been proposed for the UVA-induced CPD formation. The UVA photons directly absorbed by DNA produce CPDs with a sequence context preference different from that observed for CPDs caused by the UVC/UVB-mediated singlet/triplet excitation, causing CPD formation preferentially at thymine-containing dipyrimidine sites and probably also preferably at methyl CpG-associated dipyrimidine sites, which include the TCG sequence. In this review, I present a mechanistic consideration on the wavelength-dependent variation of the sequence context preference of the UVR-specific mutations and rationalize the proposition of the UVA-signature mutation, in addition to the UV-signature mutation.
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Affiliation(s)
- Hironobu Ikehata
- Department of Medical Biochemistry, Tohoku University Graduate School of Medicine, Sendai, Japan.
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5
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Douki T, von Koschembahr A, Cadet J. Insight in DNA Repair of UV-induced Pyrimidine Dimers by Chromatographic Methods. Photochem Photobiol 2017; 93:207-215. [PMID: 27935042 DOI: 10.1111/php.12685] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 11/21/2016] [Indexed: 01/15/2023]
Abstract
UV-induced formation of pyrimidine dimers in DNA is a major deleterious event in both eukaryotic and prokaryotic cells. Accumulation of cyclobutane pyrimidine dimers and pyrimidine (6-4) pyrimidone photoproducts can lead to cell death or be at the origin of mutations. In skin, UV induction of DNA damage is a major initiating event in tumorigenesis. To counteract these deleterious effects, all cell types possess DNA repair machinery, such as nucleotide excision repair and, in some cell types, direct reversion. Different analytical approaches were used to assess the efficiency of repair and decipher the enzymatic mechanisms. We presently review the information provided by chromatographic methods, which are complementary to biochemical assays, such as immunological detection and electrophoresis-based techniques. Chromatographic assays are interesting in their ability to provide quantitative data on a wide range of damage and are also valuable tools for the identification of repair intermediates.
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Affiliation(s)
- Thierry Douki
- Univ. Grenoble Alpes, INAC, LCIB, LAN, Grenoble, France.,CEA, INAC, SyMMES, LAN, Grenoble, France
| | - Anne von Koschembahr
- Univ. Grenoble Alpes, INAC, LCIB, LAN, Grenoble, France.,CEA, INAC, SyMMES, LAN, Grenoble, France
| | - Jean Cadet
- Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, QC, Canada
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6
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Genna V, Gaspari R, Dal Peraro M, De Vivo M. Cooperative motion of a key positively charged residue and metal ions for DNA replication catalyzed by human DNA Polymerase-η. Nucleic Acids Res 2016; 44:2827-36. [PMID: 26935581 PMCID: PMC4824119 DOI: 10.1093/nar/gkw128] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 02/19/2016] [Indexed: 12/18/2022] Open
Abstract
Trans-lesion synthesis polymerases, like DNA Polymerase-η (Pol-η), are essential for cell survival. Pol-η bypasses ultraviolet-induced DNA damages via a two-metal-ion mechanism that assures DNA strand elongation, with formation of the leaving group pyrophosphate (PPi). Recent structural and kinetics studies have shown that Pol-η function depends on the highly flexible and conserved Arg61 and, intriguingly, on a transient third ion resolved at the catalytic site, as lately observed in other nucleic acid-processing metalloenzymes. How these conserved structural features facilitate DNA replication, however, is still poorly understood. Through extended molecular dynamics and free energy simulations, we unravel a highly cooperative and dynamic mechanism for DNA elongation and repair, which is here described by an equilibrium ensemble of structures that connect the reactants to the products in Pol-η catalysis. We reveal that specific conformations of Arg61 help facilitate the recruitment of the incoming base and favor the proper formation of a pre-reactive complex in Pol-η for efficient DNA editing. Also, we show that a third transient metal ion, which acts concertedly with Arg61, serves as an exit shuttle for the leaving PPi. Finally, we discuss how this effective and cooperative mechanism for DNA repair may be shared by other DNA-repairing polymerases.
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Affiliation(s)
- Vito Genna
- Laboratory of Molecular Modeling & Drug Discovery, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genoa, Italy
| | - Roberto Gaspari
- CONCEPT Lab., Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genoa, Italy
| | - Matteo Dal Peraro
- Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland Swiss Institute of Bioinformatics (SIB), CH-1015, Lausanne, Switzerland
| | - Marco De Vivo
- Laboratory of Molecular Modeling & Drug Discovery, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genoa, Italy IAS-5 / INM-9 Computational Biomedicine Forschungszentrum Jülich, Wilhelm-Johnen-Straße 52428 Jülich, Germany
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7
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Ghodke PP, Gore KR, Harikrishna S, Samanta B, Kottur J, Nair DT, Pradeepkumar PI. The N(2)-Furfuryl-deoxyguanosine Adduct Does Not Alter the Structure of B-DNA. J Org Chem 2016; 81:502-11. [PMID: 26650891 DOI: 10.1021/acs.joc.5b02341] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
N(2)-Furfuryl-deoxyguanosine (fdG) is carcinogenic DNA adduct that originates from furfuryl alcohol. It is also a stable structural mimic of the damage induced by the nitrofurazone family of antibiotics. For the structural and functional studies of this model N(2)-dG adduct, reliable and rapid access to fdG-modified DNAs are warranted. Toward this end, here we report the synthesis of fdG-modified DNAs using phosphoramidite chemistry involving only three steps. The functional integrity of the modified DNA has been verified by primer extension studies with DNA polymerases I and IV from E. coli. Introduction of fdG into a DNA duplex decreases the Tm by ∼1.6 °C/modification. Molecular dynamics simulations of a DNA duplex bearing the fdG adduct revealed that though the overall B-DNA structure is maintained, this lesion can disrupt W-C H-bonding, stacking interactions, and minor groove hydrations to some extent at the modified site, and these effects lead to slight variations in the local base pair parameters. Overall, our studies show that fdG is tolerated at the minor groove of the DNA to a better extent compared with other bulky DNA damages, and this property will make it difficult for the DNA repair pathways to detect this adduct.
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Affiliation(s)
- Pratibha P Ghodke
- Department of Chemistry, Indian Institute of Technology Bombay , Mumbai-400076, India
| | - Kiran R Gore
- Department of Chemistry, Indian Institute of Technology Bombay , Mumbai-400076, India.,Department of Chemistry, University of Mumbai , Mumbai-400098, India
| | - S Harikrishna
- Department of Chemistry, Indian Institute of Technology Bombay , Mumbai-400076, India
| | - Biswajit Samanta
- Department of Chemistry, Indian Institute of Technology Bombay , Mumbai-400076, India
| | - Jithesh Kottur
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, Third Milestone, Faridabad-Gurgaon Expressway, Faridabad-121001, India.,Manipal University, Manipal-576104, India
| | - Deepak T Nair
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, Third Milestone, Faridabad-Gurgaon Expressway, Faridabad-121001, India.,National Centre for Biological Sciences (NCBS-TIFR), GKVK Campus, Bellary Road, Bangalore-560065, India
| | - P I Pradeepkumar
- Department of Chemistry, Indian Institute of Technology Bombay , Mumbai-400076, India
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8
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Abstract
All living organisms are continually exposed to agents that damage their DNA, which threatens the integrity of their genome. As a consequence, cells are equipped with a plethora of DNA repair enzymes to remove the damaged DNA. Unfortunately, situations nevertheless arise where lesions persist, and these lesions block the progression of the cell's replicase. In these situations, cells are forced to choose between recombination-mediated "damage avoidance" pathways or a specialized DNA polymerase (pol) to traverse the blocking lesion. The latter process is referred to as Translesion DNA Synthesis (TLS). As inferred by its name, TLS not only results in bases being (mis)incorporated opposite DNA lesions but also bases being (mis)incorporated downstream of the replicase-blocking lesion, so as to ensure continued genome duplication and cell survival. Escherichia coli and Salmonella typhimurium possess five DNA polymerases, and while all have been shown to facilitate TLS under certain experimental conditions, it is clear that the LexA-regulated and damage-inducible pols II, IV, and V perform the vast majority of TLS under physiological conditions. Pol V can traverse a wide range of DNA lesions and performs the bulk of mutagenic TLS, whereas pol II and pol IV appear to be more specialized TLS polymerases.
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9
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McIntyre J, Woodgate R. Regulation of translesion DNA synthesis: Posttranslational modification of lysine residues in key proteins. DNA Repair (Amst) 2015; 29:166-79. [PMID: 25743599 PMCID: PMC4426011 DOI: 10.1016/j.dnarep.2015.02.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 02/09/2015] [Accepted: 02/10/2015] [Indexed: 01/30/2023]
Abstract
Posttranslational modification of proteins often controls various aspects of their cellular function. Indeed, over the past decade or so, it has been discovered that posttranslational modification of lysine residues plays a major role in regulating translesion DNA synthesis (TLS) and perhaps the most appreciated lysine modification is that of ubiquitination. Much of the recent interest in ubiquitination stems from the fact that proliferating cell nuclear antigen (PCNA) was previously shown to be specifically ubiquitinated at K164 and that such ubiquitination plays a key role in regulating TLS. In addition, TLS polymerases themselves are now known to be ubiquitinated. In the case of human polymerase η, ubiquitination at four lysine residues in its C-terminus appears to regulate its ability to interact with PCNA and modulate TLS. Within the past few years, advances in global proteomic research have revealed that many proteins involved in TLS are, in fact, subject to a previously underappreciated number of lysine modifications. In this review, we will summarize the known lysine modifications of several key proteins involved in TLS; PCNA and Y-family polymerases η, ι, κ and Rev1 and we will discuss the potential regulatory effects of such modification in controlling TLS in vivo.
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Affiliation(s)
- Justyna McIntyre
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, ul. Pawinskiego 5a, 02-106 Warsaw, Poland.
| | - Roger Woodgate
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA
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10
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Ikehata H, Chang Y, Yokoi M, Yamamoto M, Hanaoka F. Remarkable induction of UV-signature mutations at the 3'-cytosine of dipyrimidine sites except at 5'-TCG-3' in the UVB-exposed skin epidermis of xeroderma pigmentosum variant model mice. DNA Repair (Amst) 2014; 22:112-22. [PMID: 25128761 DOI: 10.1016/j.dnarep.2014.07.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 07/12/2014] [Accepted: 07/21/2014] [Indexed: 10/24/2022]
Abstract
The human POLH gene is responsible for the variant form of xeroderma pigmentosum (XP-V), a genetic disease highly susceptible to cancer on sun-exposed skin areas, and encodes DNA polymerase η (polη), which is specialized for translesion DNA synthesis (TLS) of UV-induced DNA photolesions. We constructed polη-deficient mice transgenic with lacZ mutational reporter genes to study the effect of Polh null mutation (Polh(-/-)) on mutagenesis in the skin after UVB irradiation. UVB induced lacZ mutations with remarkably higher frequency in the Polh(-/-) epidermis and dermis than in the wild-type (Polh(+/+)) and heterozygote. DNA sequences of a hundred lacZ mutants isolated from the epidermis of four UVB-exposed Polh(-/-) mice were determined and compared with mutant sequences from irradiated Polh(+)(/)(+) mice. The spectra of the mutations in the two genotypes were both highly UV-specific and dominated by C→T transitions at dipyrimidines, namely UV-signature mutations. However, sequence preferences of the occurrence of UV-signature mutations were quite different between the two genotypes: the mutations occurred at a higher frequency preferentially at the 5'-TCG-3' sequence context than at the other dipyrimidine contexts in the Polh(+/+) epidermis, whereas the mutations were induced remarkably and exclusively at the 3'-cytosine of almost all dipyrimidine contexts with no preference for 5'-TCG-3' in the Polh(-/-) epidermis. In addition, in Polh(-/-) mice, a small but remarkable fraction of G→T transversions was also observed exclusively at the 3'-cytosine of dipyrimidine sites, strongly suggesting that these transversions resulted not from oxidative damage but from UV photolesions. These results would reflect the characteristics of the error-prone TLS functioning in the bypass of UV photolesions in the absence of polη, which would be mediated by mechanisms based on the two-step model of TLS. On the other hand, the deamination model would explain well the mutation spectrum in the Polh(+/+) genotype.
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Affiliation(s)
- Hironobu Ikehata
- Department of Cell Biology, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan; Department of Physiological Sciences, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan.
| | - Yumin Chang
- Department of Cell Biology, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan
| | - Masayuki Yokoi
- Department of Life Science, Faculty of Science, Gakushuin University, Tokyo 171-8588, Japan
| | - Masayuki Yamamoto
- Department of Physiological Sciences, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan
| | - Fumio Hanaoka
- Department of Life Science, Faculty of Science, Gakushuin University, Tokyo 171-8588, Japan
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11
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Y-family DNA polymerases and their role in tolerance of cellular DNA damage. Nat Rev Mol Cell Biol 2012; 13:141-52. [PMID: 22358330 DOI: 10.1038/nrm3289] [Citation(s) in RCA: 490] [Impact Index Per Article: 40.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The past 15 years have seen an explosion in our understanding of how cells replicate damaged DNA and how this can lead to mutagenesis. The Y-family DNA polymerases lie at the heart of this process, which is commonly known as translesion synthesis. This family of polymerases has unique features that enable them to synthesize DNA past damaged bases. However, as they exhibit low fidelity when copying undamaged DNA, it is essential that they are only called into play when they are absolutely required. Several layers of regulation ensure that this is achieved.
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12
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Cleaver JE. γH2Ax: biomarker of damage or functional participant in DNA repair "all that glitters is not gold!". Photochem Photobiol 2011; 87:1230-9. [PMID: 21883247 DOI: 10.1111/j.1751-1097.2011.00995.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The phosphorylation of H2Ax on its S139 site, γH2Ax, is important for the assembly of repair complexes at DNA double strand breaks (DSBs). The formation and functional role of γH2Ax after other kinds of DNA damage, especially UV light, where DSBs are rare, is less clear. Following UV light in the UVB and UVC ranges, complex distributions of γH2Ax can be identified, quite unlike the discrete enumerable foci seen after ionizing radiation. Several distinct distributions of γH2Ax occur: a low level nuclear-wide distribution of γH2Ax occurs during nucleotide excision repair; irregular focal distributions occur at arrested replication forks; high intensity nuclear-wide γH2Ax occurs in association with S-phase apoptosis. The intensity and distributions of γH2Ax vary according to the activity of excision repair, bypass polymerase and apoptotic caspases. The frequency of DSBs at arrested replication forks is low but highly variable in different cell types, and probably caused by enzymatic action. Despite the prominence of S139 phosphorylation following UV damage, mutation of this site has no influence on the UV damage response indicating that γH2Ax is a biomarker but not a participant in the UV-DNA damage response.
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Affiliation(s)
- James E Cleaver
- Department of Dermatology, University of California, San Francisco, CA, USA.
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13
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Hirota K, Sonoda E, Kawamoto T, Motegi A, Masutani C, Hanaoka F, Szüts D, Iwai S, Sale JE, Lehmann A, Takeda S. Simultaneous disruption of two DNA polymerases, Polη and Polζ, in Avian DT40 cells unmasks the role of Polη in cellular response to various DNA lesions. PLoS Genet 2010; 6. [PMID: 20949111 PMCID: PMC2951353 DOI: 10.1371/journal.pgen.1001151] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Accepted: 09/08/2010] [Indexed: 12/18/2022] Open
Abstract
Replicative DNA polymerases are frequently stalled by DNA lesions. The resulting replication blockage is released by homologous recombination (HR) and translesion DNA synthesis (TLS). TLS employs specialized TLS polymerases to bypass DNA lesions. We provide striking in vivo evidence of the cooperation between DNA polymerase η, which is mutated in the variant form of the cancer predisposition disorder xeroderma pigmentosum (XP-V), and DNA polymerase ζ by generating POLη−/−/POLζ−/− cells from the chicken DT40 cell line. POLζ−/− cells are hypersensitive to a very wide range of DNA damaging agents, whereas XP-V cells exhibit moderate sensitivity to ultraviolet light (UV) only in the presence of caffeine treatment and exhibit no significant sensitivity to any other damaging agents. It is therefore widely believed that Polη plays a very specific role in cellular tolerance to UV-induced DNA damage. The evidence we present challenges this assumption. The phenotypic analysis of POLη−/−/POLζ−/− cells shows that, unexpectedly, the loss of Polη significantly rescued all mutant phenotypes of POLζ−/− cells and results in the restoration of the DNA damage tolerance by a backup pathway including HR. Taken together, Polη contributes to a much wide range of TLS events than had been predicted by the phenotype of XP-V cells. DNA replication is a fragile biochemical reaction, as the replicative DNA polymerases are readily stalled by DNA lesions. The resulting replication blockage is released by translesion DNA synthesis (TLS), which employs specialized TLS polymerases to bypass DNA lesions. There are at least seven TLS polymerases known in vertebrates. However, how they cooperate in vivo remains one of central questions in the field. We analyzed this functional interaction by genetically disrupting two of major TLS polymerases, Polη and Polζ, in the unique genetic model organism, chicken DT40 cells. Currently, it is widely believed that Polη plays a very specific role in cellular tolerance to ultraviolet light–induced DNA damage. Polζ, on the other hand, plays a key role in cellular tolerance to a very wide range of DNA–damaging agents, as POLζ−/− cells are hypersensitivity to a number of DNA damaging agents. Our phenotypic analysis of POLη−/−/POLζ−/− cells shows that, unexpectedly, the loss of Polη significantly rescued all mutant phenotypes of POLζ−/− cells. The genetic interaction shown here reveals a previously unappreciated role of human Polη in cellular response to a wide variety of DNA lesions and two-step collaborative action of Polymerase η and ζ.
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Affiliation(s)
- Kouji Hirota
- CREST Research Project, Japan Science and Technology, Radiation Genetics, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Eiichiro Sonoda
- CREST Research Project, Japan Science and Technology, Radiation Genetics, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Takuo Kawamoto
- CREST Research Project, Japan Science and Technology, Radiation Genetics, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Akira Motegi
- CREST Research Project, Japan Science and Technology, Radiation Genetics, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Chikahide Masutani
- Solution-Oriented Research for Science and Technology (SORST), Japan Science and Technology Agency, Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Fumio Hanaoka
- Solution-Oriented Research for Science and Technology (SORST), Japan Science and Technology Agency, Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Dávid Szüts
- St. George's, University of London, London, United Kingdom
| | - Shigenori Iwai
- Division of Chemistry, Graduate School of Engineering Science, Osaka University, Osaka, Japan
| | - Julian E. Sale
- Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Alan Lehmann
- Genome Damage and Stability Centre, University of Sussex, Brighton, United Kingdom
| | - Shunichi Takeda
- CREST Research Project, Japan Science and Technology, Radiation Genetics, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- * E-mail:
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14
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Fernandes PH, Lloyd RS. Mutagenic bypass of the butadiene-derived 2'-deoxyuridine adducts by polymerases eta and zeta. Mutat Res 2007; 625:40-9. [PMID: 17586533 PMCID: PMC2180188 DOI: 10.1016/j.mrfmmm.2007.05.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2007] [Revised: 05/08/2007] [Accepted: 05/10/2007] [Indexed: 01/13/2023]
Abstract
Butadiene is a ubiquitous environmental chemical carcinogen that when activated to its monoepoxide intermediate can react with the N3 position of cytosine, resulting in two stereoisomeric adducted bases that rapidly deaminate to N3 2'-deoxyuridine lesions. We have previously shown that replication of DNAs containing these adducts through mammalian cells resulted in approximately 97% mutagenicity, predominantly C to T transitions. Since replicative DNA polymerases were blocked by these lesions in vitro, translesional polymerases were assessed for their ability to bypass these adducts. While polymerases iota, kappa and zeta were significantly blocked one nucleotide prior to the lesion, pol eta incorporated nucleotides opposite the adducts with a preference for insertion of a G or A. Following polymerase dissociation and reassociation, pol eta was also able to extend primers with mispaired termini opposite the lesions, with extensions from the A and T mismatched primer termini being the most efficient. Pol zeta was also able to extend primers containing all mismatched nucleotides opposite the lesions, with the most efficient extension occurring off of the A mismatched primer.
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Affiliation(s)
| | - R. Stephen Lloyd
- To whom correspondence should be addressed at Center for Research on Occupational and Environmental Toxicology, 3181 SW Sam Jackson Park Rd, Portland, OR 97239, Tel. 503 494−9957; Fax. 503 494−6831,
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15
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Lone S, Romano LJ. The role of specific amino acid residues in the active site of Escherichia coli DNA polymerase I on translesion DNA synthesis across from and past an N-2-aminofluorene adduct. Biochemistry 2007; 46:2599-607. [PMID: 17305316 DOI: 10.1021/bi061324o] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Understanding how carcinogenic DNA adducts compromise accurate DNA replication is an important goal in cancer research. A central part of these studies is to determine the molecular mechanism that allows a DNA polymerase to incorporate a nucleotide across from and past a bulky adduct in a DNA template. To address the importance of polymerase architecture on replication across from this type of bulky DNA adduct, three active-site mutants of Escherichia coli DNA polymerase I (Klenow fragment) were used to study DNA synthesis on DNA modified with the carcinogen N-2-aminofluorene (AF). Running-start synthesis studies showed that full-length synthesis past the AF adduct was inhibited for all of the mutants, but that this inhibition was substantially less for the F762A mutant. Single nucleotide extension and steady-state kinetic experiments showed that the Y766S mutant displayed higher rates of insertion of each incorrect nucleotide relative to WT across from the dG-AF adduct. This effect was not observed for F762A or E710A mutants. Similar experiments that measured synthesis one nucleotide past the dG-AF adduct revealed an enhanced preference by the F762A mutant for dG opposite the T at this position. Finally, synthesis at the +1 and +2 positions was inhibited to a greater extent for the Y766S and E710A mutants compared with both the WT and F762A mutants. Taken together, this work is consistent with the model that polymerase geometry plays a crucial role in both the insertion and extension steps during replication across from bulky DNA lesions.
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Affiliation(s)
- Samer Lone
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
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16
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Zhong X, Garg P, Stith CM, McElhinny SAN, Kissling GE, Burgers PMJ, Kunkel TA. The fidelity of DNA synthesis by yeast DNA polymerase zeta alone and with accessory proteins. Nucleic Acids Res 2006; 34:4731-42. [PMID: 16971464 PMCID: PMC1635245 DOI: 10.1093/nar/gkl465] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
DNA polymerase zeta (pol zeta) participates in several DNA transactions in eukaryotic cells that increase spontaneous and damage-induced mutagenesis. To better understand this central role in mutagenesis in vivo, here we report the fidelity of DNA synthesis in vitro by yeast pol zeta alone and with RFC, PCNA and RPA. Overall, the accessory proteins have little effect on the fidelity of pol zeta. Pol zeta is relatively accurate for single base insertion/deletion errors. However, the average base substitution fidelity of pol zeta is substantially lower than that of homologous B family pols alpha, delta and epsilon. Pol zeta is particularly error prone for substitutions in specific sequence contexts and generates multiple single base errors clustered in short patches at a rate that is unprecedented in comparison with other polymerases. The unique error specificity of pol zeta in vitro is consistent with Pol zeta-dependent mutagenic specificity reported in vivo. This fact, combined with the high rate of single base substitution errors and complex mutations observed here, indicates that pol zeta contributes to mutagenesis in vivo not only by extending mismatches made by other polymerases, but also by directly generating its own mismatches and then extending them.
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Affiliation(s)
| | - Parie Garg
- Department of Biochemistry and Molecular Biophysics, Washington University School of MedicineSt Louis, MO 63110, USA
| | - Carrie M. Stith
- Department of Biochemistry and Molecular Biophysics, Washington University School of MedicineSt Louis, MO 63110, USA
| | | | - Grace E. Kissling
- Biostatistics Branch, National Institute of Environmental Health Sciences, NIH, DHHSResearch Triangle Park, NC 27709, USA
| | - Peter M. J. Burgers
- Department of Biochemistry and Molecular Biophysics, Washington University School of MedicineSt Louis, MO 63110, USA
| | - Thomas A. Kunkel
- To whom correspondence should be addressed at: Bldg 101, Room E342B, 111 T.W. Alexander Drive, Research Triangle Park, NC 27709-2233, USA. Tel: +1 919 541 2644; Fax: +1 919 541 7613;
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17
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Garg P, Burgers PM. Ubiquitinated proliferating cell nuclear antigen activates translesion DNA polymerases eta and REV1. Proc Natl Acad Sci U S A 2005; 102:18361-6. [PMID: 16344468 PMCID: PMC1317920 DOI: 10.1073/pnas.0505949102] [Citation(s) in RCA: 194] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In response to DNA damage, the Rad6/Rad18 ubiquitin-conjugating complex monoubiquitinates the replication clamp proliferating cell nuclear antigen (PCNA) at Lys-164. Although ubiquitination of PCNA is recognized as an essential step in initiating postreplication repair, the mechanistic relevance of this modification has remained elusive. Here, we describe a robust in vitro system that ubiquitinates yeast PCNA specifically on Lys-164. Significantly, only those PCNA clamps that are appropriately loaded around effector DNA by its loader, replication factor C, are ubiquitinated. This observation suggests that, in vitro, only PCNA present at stalled replication forks is ubiquitinated. Ubiquitinated PCNA displays the same replicative functions as unmodified PCNA. These functions include loading onto DNA by replication factor C, as well as Okazaki fragment synthesis and maturation by the PCNA-coordinated actions of DNA polymerase delta, the flap endonuclease FEN1, and DNA ligase I. However, whereas the activity of DNA polymerase zeta remains unaffected by ubiquitination of PCNA, ubiquitinated PCNA specifically activates two key enzymes in translesion synthesis: DNA polymerase eta, the yeast Xeroderma pigmentosum ortholog, and Rev1, a deoxycytidyl transferase that functions in organizing the mutagenic DNA replication machinery. We propose that ubiquitination of PCNA increases its functionality as a sliding clamp to promote mutagenic DNA replication.
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Affiliation(s)
- Parie Garg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 South Euclid, St. Louis, MO 63110, USA
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18
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Abstract
When cells that are actively replicating DNA encounter sites of base damage or strand breaks, replication might stall or arrest. In this situation, cells rely on DNA-damage-tolerance mechanisms to bypass the damage effectively. One of these mechanisms, known as translesion DNA synthesis, is supported by specialized DNA polymerases that are able to catalyse nucleotide incorporation opposite lesions that cannot be negotiated by high-fidelity replicative polymerases. A second category of tolerance mechanism involves alternative replication strategies that obviate the need to replicate directly across sites of template-strand damage.
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Affiliation(s)
- Errol C Friedberg
- Laboratory of Molecular Pathology, Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9072, USA.
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19
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King NM, Nikolaishvili-Feinberg N, Bryant MF, Luche DD, Heffernan TP, Simpson DA, Hanaoka F, Kaufmann WK, Cordeiro-Stone M. Overproduction of DNA polymerase eta does not raise the spontaneous mutation rate in diploid human fibroblasts. DNA Repair (Amst) 2005; 4:714-24. [PMID: 15886068 DOI: 10.1016/j.dnarep.2005.04.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2005] [Revised: 03/31/2005] [Accepted: 04/01/2005] [Indexed: 11/22/2022]
Abstract
Telomerase-immortalized lines of diploid xeroderma pigmentosum variant (XP-V) fibroblasts (XP115LO and XP4BE) were complemented for constitutive or regulated expression of wild-type human DNA polymerase eta (hpol eta). The ectopic gene was expressed from a retroviral LTR at a population average of 34- to 59-fold above the endogenous (mutated) mRNA and high levels of hpol eta were detected by immunoblotting. The POLH cDNA was also cloned downstream from an ecdysone-regulated promoter and transduced into the same recipient cells. Abundance of the wild-type mRNA increased approximately 10-fold by addition of ponasterone to the culture medium. Complemented cell lines acquired normal resistance to the cytotoxic effects of UVC, even in the presence of 1mM caffeine. They also tolerated higher levels of UVC-induced template lesions during nascent DNA elongation when compared to normal fibroblasts (NHF). UVC-induced mutation frequencies at the hypoxanthine-guanine phosphoribosyl transferase (HPRT) locus were measured in the XP115LO+XPV cell line overproducing hpol eta constitutively (E. Bassett, N.M. King, M.F. Bryant, S. Hector, L. Pendyala, S.G. Chaney, M. Cordeiro-Stone, The role of DNA polymerase eta in translesion synthesis past platinum-DNA adducts in human fibroblasts, Cancer Res. 64 (2004) 6469-6475). Induced mutation frequencies were significantly reduced, even below those observed in NHF; however, the average mutation frequency in untreated cultures was about three-fold higher than in the isogenic vector-control cell line. In this study, spontaneous HPRT mutation frequencies were measured at regular intervals, as isogenic fibroblasts either lacking or overproducing hpol eta were expanded for 100 population doublings. The mutation rates estimated from these results were not significantly increased in XP115LO cells expressing abnormal levels of hpol eta, relative to the cells lacking this specialized polymerase. These findings suggest that diploid human fibroblasts with normal DNA repair capacities and intact checkpoints are well protected against the potential mutagenic outcome of overproducing hpol eta, while still benefiting from accurate translesion synthesis of UV-induced pyrimidine dimers.
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Affiliation(s)
- Nicole M King
- Department of Pathology and Laboratory Medicine, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7525, USA
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20
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Yagi Y, Ogawara D, Iwai S, Hanaoka F, Akiyama M, Maki H. DNA polymerases eta and kappa are responsible for error-free translesion DNA synthesis activity over a cis-syn thymine dimer in Xenopus laevis oocyte extracts. DNA Repair (Amst) 2005; 4:1252-69. [PMID: 16055392 DOI: 10.1016/j.dnarep.2005.06.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2005] [Revised: 06/15/2005] [Accepted: 06/17/2005] [Indexed: 10/25/2022]
Abstract
In translesion synthesis (TLS), specialized DNA polymerases (pols) facilitate progression of replication forks stalled by DNA damage. Although multiple TLS pols have been identified in eukaryotes, little is known about endogenous TLS pols and their relative contributions to TLS in vivo because of their low cellular abundance. Taking advantage of Xenopus laevis oocyte cells, with their extraordinary size and abundant enzymes involved in DNA metabolism, we have identified and characterized endogenous TLS pols for DNA damage induced by ultraviolet (UV) irradiation. We designed a TLS assay which monitors primer elongation on a synthetic oligomer template over a single UV-induced lesion, either a cys-syn cyclobutane pyrimidine dimer (CPD) or a pyrimidine (6-4) pyrimidone photoproduct. Four distinct TLS activities (TLS1-TLS4) were identified in X. laevis oocyte extracts, using three template/primer (T/P) DNA substrates having various sites at which primer extension is initiated relative to the lesion. TLS1 and TLS2 activities appear to be sequence-dependent. TLS3 and TLS4 extended the primers over the CPD in an error-free manner irrespective of sequence context. Base insertion opposite the CPD of the T/P substrate in which the 3'-end of the primer is placed one base upstream of the lesion was observed only with TLS3. TLS3 and TLS4 showed primer extension with similar efficiencies on the T/P substrate whose 3'-primer terminal dinucleotide (AA) was complementary to the CPD lesion. Investigations with antibodies and recombinant pols revealed that TLS3 and TLS4 were most likely attributable to pol eta and pol kappa, respectively. These results indicate that error-free insertion in CPD bypass is due mainly to pol eta (TLS3) in the extracts, and suggest that pol kappa (TLS4) may assist pol eta (TLS3) in error-free extension during CPD bypass.
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Affiliation(s)
- Yoshihiko Yagi
- Department of Molecular Biology, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5, Ikoma, Nara 630-0101, Japan
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21
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Abstract
Nucleotide-excision repair diseases exhibit cancer, complex developmental disorders and neurodegeneration. Cancer is the hallmark of xeroderma pigmentosum (XP), and neurodegeneration and developmental disorders are the hallmarks of Cockayne syndrome and trichothiodystrophy. A distinguishing feature is that the DNA-repair or DNA-replication deficiencies of XP involve most of the genome, whereas the defects in CS are confined to actively transcribed genes. Many of the proteins involved in repair are also components of dynamic multiprotein complexes, transcription factors, ubiquitylation cofactors and signal-transduction networks. Complex clinical phenotypes might therefore result from unanticipated effects on other genes and proteins.
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Affiliation(s)
- James E Cleaver
- Auerback Melanoma Laboratory, Room N431, UCSF Cancer Center, University of California, 94143-0808, USA.
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22
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Garg P, Stith CM, Majka J, Burgers PMJ. Proliferating cell nuclear antigen promotes translesion synthesis by DNA polymerase zeta. J Biol Chem 2005; 280:23446-50. [PMID: 15879599 DOI: 10.1074/jbc.c500173200] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
DNA polymerase zeta (Pol zeta), a heterodimer of Rev3 and Rev7, is essential for DNA damage provoked mutagenesis in eukaryotes. DNA polymerases that function in a processive complex with the replication clamp proliferating cell nuclear antigen (PCNA) have been shown to possess a close match to the consensus PCNA-binding motif QxxLxxFF. This consensus motif is lacking in either subunit of Pol zeta, yet its activity is stimulated by PCNA. In particular, translesion synthesis of UV damage-containing DNA is dramatically stimulated by PCNA such that translesion synthesis rates are comparable with replication rates by Pol zeta on undamaged DNA. PCNA also stimulated translesion synthesis of a model abasic site by Pol zeta. Efficient PCNA stimulation required that PCNA was prevented from sliding off the damage-containing model oligonucleotide template-primer through the use of biotin-streptavidin bumpers or other blocks. Under those experimental conditions, facile bypass of the abasic site was also detected by DNA polymerase delta or eta (Rad30). The yeast DNA damage checkpoint clamp, consisting of Rad17, Mec3, and Ddc1, and an ortholog of human 9-1-1, has been implicated in damage-induced mutagenesis. However, this checkpoint clamp did not stimulate translesion synthesis by Pol zeta or by DNA polymerase delta.
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Affiliation(s)
- Parie Garg
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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23
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Plosky BS, Woodgate R. Switching from high-fidelity replicases to low-fidelity lesion-bypass polymerases. Curr Opin Genet Dev 2004; 14:113-9. [PMID: 15196456 DOI: 10.1016/j.gde.2004.02.002] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Replication of damaged DNA often requires a DNA polymerase in addition to the cell's normal replicase. Recent research has begun to shed light on the switch from a high-fidelity replicative polymerase to a low-fidelity translesion polymerase that occurs at a stalled replication fork. A picture is emerging in which eukaryotic replicative clamps are posttranslationally modified by ubiquitination, SUMOylation or phosphorylation. It is believed that such modifications help to regulate the access of translesion polymerases to the nascent primer terminus.
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Affiliation(s)
- Brian S Plosky
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-2725, USA
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24
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Yang J, Chen Z, Liu Y, Hickey RJ, Malkas LH. Altered DNA polymerase iota expression in breast cancer cells leads to a reduction in DNA replication fidelity and a higher rate of mutagenesis. Cancer Res 2004; 64:5597-607. [PMID: 15313897 DOI: 10.1158/0008-5472.can-04-0603] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The recently discovered human enzyme DNA polymerase iota (pol iota) has been shown to have an exceptionally high error rate on artificial DNA templates. Although there is a considerable body of in vitro evidence for a role for pol iota in DNA lesion bypass, there is no in vivo evidence to confirm this action. We report here that pol iota expression is elevated in breast cancer cells and correlates with a significant decrease in DNA replication fidelity. We also demonstrate that UV treatment of breast cancer cells additionally increases pol iota expression with a peak occurring between 30 min and 2 h after cellular insult. This implies that the change in pol iota expression is an early event after UV-mediated DNA damage. That pol iota may play a role in the higher mutation frequencies observed in breast cancer cells was suggested when a reduction in mutation frequency was found after pol iota was immunodepleted from nuclear extracts of the cells. Analysis of the UV-induced mutation spectra revealed that > 90% were point mutations. The analysis also demonstrated a decreased C --> T nucleotide transition and an increased C --> A transversion rate. Overall, our data strongly suggest that pol iota may be involved in the generation of both increased spontaneous and translesion mutations during DNA replication in breast cancer cells, thereby contributing to the accumulation of genetic damage.
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Affiliation(s)
- Jin Yang
- Department of Medicine, Division of Hematology/Oncology, Cancer Research Institute, Indiana University of School of Medicine, Indianapolis, Indiana 46202, USA
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25
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Yu Y, Yang J, Zhu F, Xu F. Response of REV3 promoter to N-methyl-N'-nitro-N-nitrosoguanidine. Mutat Res 2004; 550:49-58. [PMID: 15135640 DOI: 10.1016/j.mrfmmm.2004.02.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2003] [Revised: 01/17/2004] [Accepted: 02/02/2004] [Indexed: 12/01/2022]
Abstract
Previously, we have shown that low concentration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) led to the upregulation of REV3 gene at transcriptional level in cultured human amnion FL cells. In this study, using bioinformatic analysis the putative binding sites for different transcription factors were found to exist in REV3 gene promoter region. A 2570-bp fragment of the 5' flanking region of REV3 gene was amplified by PCR from PAC clone RP3-415N12 and inserted into the pGL3-Basic reporter vector. Dual-luciferase reporter assay demonstrated that the reconstructed plasmid did respond to MNNG exposure in transfected FL cells. Several variants of the reporter plasmids with different deletions of the REV3 promoter region were also constructed and their promoter strength was analyzed. It was found that the MNNG response element might locate at the REV3 gene promoter region -404 to -102 between two Sma1 sites. The shortest responsive fragment containing the putative binding sites for transcription factors CREBP, AP-2, NF-kappaB, and SP1 was also identified.
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Affiliation(s)
- Yingnian Yu
- Department of Pathology and Pathophysiology, Center for Environmental Genomics, Zhejiang University School of Medicine, 353 Yan An Road, Hangzhou, Zhejiang 310031, China.
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26
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Vaisman A, Frank EG, Iwai S, Ohashi E, Ohmori H, Hanaoka F, Woodgate R. Sequence context-dependent replication of DNA templates containing UV-induced lesions by human DNA polymerase iota. DNA Repair (Amst) 2003; 2:991-1006. [PMID: 12967656 DOI: 10.1016/s1568-7864(03)00094-6] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Humans possess four Y-family polymerases: pols eta, iota, kappa and the Rev1 protein. The pivotal role that pol eta plays in protecting us from UV-induced skin cancers is unquestioned given that mutations in the POLH gene (encoding pol eta), lead to the sunlight-sensitive and cancer-prone xeroderma pigmentosum variant phenotype. The roles that pols iota, kappa and Rev1 play in the tolerance of UV-induced DNA damage is, however, much less clear. For example, in vitro studies in which the ability of pol iota to bypass UV-induced cyclobutane pyrimidine dimers (CPDs) or 6-4 pyrimidine-pyrimidone (6-4PP) lesions has been assayed, are somewhat varied with results ranging from limited misinsertion opposite CPDs to complete lesion bypass. We have tested the hypothesis that such discrepancies might have arisen from different assay conditions and local sequence contexts surrounding each UV-photoproduct and find that pol iota can facilitate significant levels of unassisted highly error-prone bypass of a T-T CPD, particularly when the lesion is located in a 3'-A[T-T]A-5' template sequence context and the reaction buffer contains no KCl. When encountering a T-T 6-4PP dimer under the same assay conditions, pol iota efficiently and accurately inserts the correct base, A, opposite the 3'T of the 6-4PP by factors of approximately 10(2) over the incorporation of incorrect nucleotides, while incorporation opposite the 5'T is highly mutagenic. Pol kappa has been proposed to function in the bypass of UV-induced lesions by helping extend primers terminated opposite CPDs. However, we find no evidence that the combined actions of pol iota and pol kappa result in a significant increase in bypass of T-T CPDs when compared to pol iota alone. Our data suggest that under certain conditions and sequence contexts, pol iota can bypass T-T CPDs unassisted and can efficiently incorporate one or more bases opposite a T-T 6-4PP. Such biochemical activities may, therefore, be of biological significance especially in XP-V cells lacking the primary T-T CPD bypassing enzyme, pol eta.
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Affiliation(s)
- Alexandra Vaisman
- Section on DNA Replication, Repair and Mutagenesis, Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Building 6, Room 1A13, 9000 Rockville Pike, Bethesda, MD 20892-2725,USA
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27
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Savijoki K, Ingmer H, Frees D, Vogensen FK, Palva A, Varmanen P. Heat and DNA damage induction of the LexA-like regulator HdiR from Lactococcus lactis is mediated by RecA and ClpP. Mol Microbiol 2003; 50:609-21. [PMID: 14617183 DOI: 10.1046/j.1365-2958.2003.03713.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The SOS response is a paradigm for bacterial cells response to DNA damage. Yet some bacteria lack a homologue of the SOS regulator, LexA, including the Gram-positive, Lactococcus lactis. In this organism we have identified a negative transcriptional regulator, HdiR that induces target gene expression both upon DNA damage and heat shock. Gel mobility shift assays revealed that the binding site for HdiR is located within an inverted repeat structure. HdiR is able to carry out a self-cleavage reaction in vitro at high pHs, while in vivo it undergoes RecA-dependent self-cleavage in the presence of a DNA-damaging agent. Intriguingly, the N-terminal cleavage product of HdiR retains DNA binding activity, and only when degraded by the Clp protease, is gene expression induced. Thus, the activity of HdiR in response to DNA damage is controlled by sequential proteolysis, involving self-cleavage and Clp-dependent degradation of HdiR. During heat-stress, limited self-cleavage occurs; however, recA and clpP are still required for full induction of target gene expression. Thus, our data show that common elements are involved in both the DNA damage and the heat-mediated induction of the HdiR regulon.
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Affiliation(s)
- Kirsi Savijoki
- University of Helsinki, Faculty of Veterinary Medicine, Department of Basic Veterinary Sciences, Division of Microbiology and Epidemiology, PO Box 57, 00014 Helsinki University, Helsinki, Finland
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Sonoda E, Okada T, Zhao GY, Tateishi S, Araki K, Yamaizumi M, Yagi T, Verkaik NS, van Gent DC, Takata M, Takeda S. Multiple roles of Rev3, the catalytic subunit of polzeta in maintaining genome stability in vertebrates. EMBO J 2003; 22:3188-97. [PMID: 12805232 PMCID: PMC162160 DOI: 10.1093/emboj/cdg308] [Citation(s) in RCA: 172] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Translesion DNA synthesis (TLS) and homologous DNA recombination (HR) are two major postreplicational repair (PRR) pathways. The REV3 gene of Saccharomyces cerevisiae encodes the catalytic subunit of DNA polymerase zeta, which is involved in mutagenic TLS. To investigate the role of REV3 in vertebrates, we disruped the gene in chicken DT40 cells. REV3(-/-) cells are sensitive to various DNA-damaging agents, including UV, methyl methanesulphonate (MMS), cisplatin and ionizing radiation (IR), consistent with its role in TLS. Interestingly, REV3(-/-) cells showed reduced gene targeting efficiencies and significant increase in the level of chromosomal breaks in the subsequent M phase after IR in the G(2) phase, suggesting the involvement of Rev3 in HR-mediated double-strand break repair. REV3(-/-) cells showed significant increase in sister chromatid exchange events and chromosomal breaks even in the absence of exogenous genotoxic stress. Furthermore, double mutants of REV3 and RAD54, genes involved in HR, are synthetic lethal. In conclusion, Rev3 plays critical roles in PRR, which accounts for survival on naturally occurring endogenous as well as induced damages during replication.
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Affiliation(s)
- Eiichiro Sonoda
- CREST Research Project, Japan Science and Technology, Radiation Genetics, Graduate School of Medicine, Kyoto University, Yoshida Konoe, Sakyo-ku, Kyoto 606-8501, Japan
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29
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Zhu F, Zhang M. DNA polymerase ζ: new insight into eukaryotic mutagenesis and mammalian embryonic development. World J Gastroenterol 2003; 9:1165-9. [PMID: 12800216 PMCID: PMC4611776 DOI: 10.3748/wjg.v9.i6.1165] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Information about the mechanisms that generate mutations in eukaryotes is likely to be useful for understanding human health concerns, such as genotoxicity and cancer. Eukaryotic mutagenesis is largely the outcome of attacks by endogenous and environmental agents. Except for DNA repair, cell cycle checkpoints and DNA damage avoidance, cells have also evolved DNA damage tolerance mechanism, by which lesion-targeted mutation might occur in the genome during replication by specific DNA polymerases to bypass the lesions (translesion DNA synthesis, TLS), or mutation on undamaged DNA templates (untargeted mutation) might be induced. DNA polymerase ζ (pol ζ), which was found firstly in budding yeast Saccharomyces cerevisiae and consists of catalytic subunit scRev3 and stimulating subunit scRev7, has received more attention in recent years. Pol ζ is a member of DNA polymerase δ subfamily, which belongs to DNA polymerase B family, and exists in almost all eukaryotes. Human homolog of the scRev3 gene is located in chromosome region 6q21, and the mouse equivalent maps to chromosome 10, distal to the c-myb gene and close to the Macs gene. Alternative splicing, upstream out-of frame ATG can be found in yeast scRev3, mouse and human homologs. Furthermore, the sequence from 253-323 immediate upstream of the AUG initiator codon has the potential to form a stem-loop hairpin secondary structure in REV3 mRNA, suggesting that human REV3 protein may be expressed at low levels in human cells under normal growth conditions. The functional domain analysis showed that yeast Rev3-980 tyrosine in conserved region II is at the polymerase active site. Human REV3 amino acid residues 1776-2195 provide a REV7 binding domain, and REV7 amino acid residues 1-211 provide a bind domain for REV1, REV3 and REV7 itself. More interestingly, REV7 interacts with hMAD2 and therefore might function in the cell cycle control by affecting the activation of APC (anaphase promoting complex). Currently it has been known that pol ζ is involved in most spontaneous mutation, lesion-targeted mutation via TLS, chemical carcinogen induced untargeted mutation and somatic hypermutation of antibody genes in mammalian. In TLS pathway, pol ζ acts as a "mismatch extender" with combination of other DNA polymerases, such as pol ι. Unlike in yeast, it was found that pol ζ also functioned in mouse embryonic development more recently. It was hypothesized that the roles of pol ζ in TLS and cell cycle control might contribute to mouse embryonic lethality.
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Affiliation(s)
- Feng Zhu
- Department of Pathophysiology, Zhejiang University School of Medicine, Hangzhou 310031, Zhejiang Province, China
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Abstract
Our appreciation of the DNA transactions that replicate and maintain a stable human genome is changing rapidly due to recent discoveries indicating that eukaryotic cells contain many more DNA polymerases than previously thought. This review describes emerging information on the properties and functions of human DNA polymerases, with emphasis on connections between DNA polymerase functions and cancer.
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Affiliation(s)
- Thomas A Kunkel
- Laboratory of Molecular Genetics and Laboratory of Structural Biology, National Institute of Environmental Health Sciences, NIH/DHHS, Research Triangle Park, NC 27709, USA.
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Burger A, Fix D, Liu H, Hays J, Bockrath R. In vivo deamination of cytosine-containing cyclobutane pyrimidine dimers in E. coli: a feasible part of UV-mutagenesis. Mutat Res 2003; 522:145-56. [PMID: 12517420 DOI: 10.1016/s0027-5107(02)00310-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We have estimated in vivo deamination rates for cytosines in cyclobutane pyrimidine dimers (CPD or PyPy) in UV-irradiated E. coli deficient in uracil DNA glycosylase. The protocol consisted of UV-irradiation, holding in buffer to allow for deamination of cytosines in CPDs and photoreversal (PR) to establish uracils where cytosines in CPD deaminated. The deamination rate at TC photoproducts targeting glutamine tRNA suppressor mutations was estimated from the increase in the mutation frequency after PR (MF(PR)) that developed as UV-irradiated cells were held before PR. Evidence suggested that an earlier study with this protocol under-estimated the deamination rate at sites producing the same mutations in an E. coli B/r strain. With a K12 strain, where the targeting apparently is principally by CPD and not (6-4) photoproducts, a larger rate of k = 0.0091 min(-1) at 42 degrees C resulted. The dark assay for MF also increased significantly with time for deamination consistent with a model for efficient mutation by translesion synthesis at uracil-containing CPD. In addition, we used a strain constructed by Cupples and Miller in which beta-galactosidase was inactive because -GGG- was at codon 461 and would revert to Lac(+) only when replaced by -GAG- or -GAA- for glutamate. CC photoproducts at this target site in the opposite DNA strand could reveal effects of first and second deaminations in the same CPD. MF(PR) for Lac(+) mutations increased and then decreased as a function of deamination time (at six temperatures 36-48 degrees C). Fitting an approximate model equation that distinguished two different deamination rates to these data suggested a first deamination producing Lac(+) at a rate about eight-fold less than a second deamination restoring the Lac(-) phenotype. We conclude that deamination, changing a cytosine-containing CPD to a uracil-containing CPD, could be an integral part of UV-induced C-to-T mutations.
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Affiliation(s)
- A Burger
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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32
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Abstract
Based upon phylogenetic relationships, the broad Y-family of DNA polymerases can be divided into various subfamilies consisting of UmuC (polV)-like; DinB (polIV/polkappa)-like; Rev1-like, Rad30A (poleta)-like and Rad30B (poliota)-like polymerases. The polIV/polkappa-like polymerases are most ubiquitous, having been identified in bacteria, archaea and eukaryotes. In contrast, the polV-like polymerases appear restricted to bacteria (both Gram positive and Gram negative). Rev1 and poleta-like polymerases are found exclusively in eukaryotes, and to date, poliota-like polymerases have only been identified in higher eukaryotes. In general, the in vitro properties of polymerases characterized within each sub-family are quite similar. An exception to this rule occurs with the poliota-like polymerases, where the enzymatic properties of Drosophila melanogaster poliota are more similar to that of Saccharomyces cerevisiae and human poleta than to the related human poliota. For example, like poleta, Drosophila poliota can bypass a cis-syn thymine-thymine dimer both accurately and efficiently, while human poliota bypasses the same lesion inefficiently and with low-fidelity. Even in cases where human poliota can efficiently insert a base opposite a lesion (such as a synthetic abasic site, the 3'T of a 6-4-thymine-thymine pyrimidine-pyrimidone photoproduct or opposite benzo[a]pyrene diol epoxide deoxyadenosine adducts), further extension is often limited. Thus, although poliota most likely arose from a genetic duplication of poleta millions of years ago as eukaryotes evolved, it would appear that poliota from humans (and possibly all mammals) has been further subjected to evolutionary pressures that have "tailored" its enzymatic properties away from lesion bypass and towards other function(s) specific for higher eukaryotes. The identification of such functions and the role that mammalian poliota plays in lesion bypass in vivo, should hopefully be forthcoming with the construction of human cell lines deleted for poliota and the identification of mice deficient in poliota.
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Affiliation(s)
- Alexandra Vaisman
- Section on DNA Replication, Repair and Mutagenesis, National Institute of Child Health and Human Development, National Institutes of Health, Building 6, Room 1A13, 9000 Rockville Pike, Bethesda, MD 20892-2725, USA
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Okada T, Sonoda E, Yamashita YM, Koyoshi S, Tateishi S, Yamaizumi M, Takata M, Ogawa O, Takeda S. Involvement of vertebrate polkappa in Rad18-independent postreplication repair of UV damage. J Biol Chem 2002; 277:48690-5. [PMID: 12356753 DOI: 10.1074/jbc.m207957200] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
DNA damage, which is left unrepaired by excision repair pathways, often blocks replication, leading to lesions such as breaks and gaps on the sister chromatids. These lesions may be processed by either homologous recombination (HR) repair or translesion DNA synthesis (TLS). Vertebrate Polkappa belongs to the DNA polymerase Y family, as do most TLS polymerases. However, the role for Polkappa in vertebrate cells is unclear because of the lack of reverse genetic studies. Here, we generated cells deficient in Polkappa (polkappa cells) from the chicken B lymphocyte line DT40. Although purified Polkappa is unable to bypass ultraviolet (UV) damage, polkappa cells exhibited increased UV sensitivity, and the phenotype was suppressed by expression of human and chicken Polkappa, suggesting that Polkappa is involved in TLS of UV photoproduct. Defects in both Polkappa and Rad18, which regulates TLS in yeast, in DT40 showed an additive effect on UV sensitivity. Interestingly, the level of sister chromatid exchange, which reflects HR-mediated repair, was elevated in normally cycling polkappa cells. This implies functional redundancy between HR and Polkappa in maintaining chromosomal DNA. In conclusion, vertebrate Polkappa is involved in Rad18-independent TLS of UV damage and plays a role in maintaining genomic stability.
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Affiliation(s)
- Takashi Okada
- Department of Radiation Genetics, Kyoto University Graduate School of Medicine, Japan
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35
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Frank EG, Sayer JM, Kroth H, Ohashi E, Ohmori H, Jerina DM, Woodgate R. Translesion replication of benzo[a]pyrene and benzo[c]phenanthrene diol epoxide adducts of deoxyadenosine and deoxyguanosine by human DNA polymerase iota. Nucleic Acids Res 2002; 30:5284-92. [PMID: 12466554 PMCID: PMC137958 DOI: 10.1093/nar/gkf643] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2002] [Revised: 10/07/2002] [Accepted: 10/07/2002] [Indexed: 11/13/2022] Open
Abstract
Human DNA polymerase iota (poliota) is a Y-family polymerase whose cellular function is presently unknown. Here, we report on the ability of poliota to bypass various stereoisomers of benzo[a]pyrene (BaP) diol epoxide (DE) and benzo[c]phenanthrene (BcPh) DE adducts at deoxyadenosine (dA) or deoxyguanosine (dG) bases in four different template sequence contexts in vitro. We find that the BaP DE dG adducts pose a strong block to poliota-dependent replication and result in a high frequency of base misincorporations. In contrast, misincorporations opposite BaP DE and BcPh DE dA adducts generally occurred with a frequency ranging between 2 x 10(-3) and 6 x 10(-4). Although dTMP was inserted efficiently opposite all dA adducts, further extension was relatively poor, with one exception (a cis opened adduct derived from BcPh DE) where up to 58% extension past the lesion was observed. Interestingly, another human Y-family polymerase, polkappa, was able to extend dTMP inserted opposite a BaP DE dA adduct. We suggest that poliota might therefore participate in the error-free bypass of DE-adducted dA in vivo by predominantly incorporating dTMP opposite the damaged base. In many cases, elongation would, however, require the participation of another polymerase more specialized in extension, such as polkappa.
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Affiliation(s)
- Ekaterina G Frank
- Section on DNA Replication, Repair, and Mutagenesis, Building 6, Room 1A13, National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892-2725 USA
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Burger A, Raymer J, Bockrath R. DNA damage-processing in E. coli: on-going protein synthesis is required for fixation of UV-induced lethality and mutation. DNA Repair (Amst) 2002; 1:821-31. [PMID: 12531029 DOI: 10.1016/s1568-7864(02)00107-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
UV irradiation of E. coli produces photoproducts in the DNA genome. In consequence, some bacteria lose viability (colony-forming ability) or remain viable as mutant cells. However, the end-points of viability inactivation (lethality) or mutation are determined by cellular processes that act on the UV-damaged DNA. We have investigated the in vivo time course for processes that deal with cyclobutane pyrimidine dimers (CPD) which can be specifically removed by photoreactivation (PR). At different times during post-UV incubation, samples were challenged with PR and assayed for viability or mutation. We used excision-defective E. coli B/r cells and worked under yellow light to avoid background PR. During post-UV incubation (0-100min) in fully supplemented defined medium, inactivation and mutation were initially significantly reversed by PR but the extent of this reversal decreased during continued incubation defining "fixation" of lethality or mutation, respectively. In contrast, if protein synthesis was restricted during the post-UV incubation, no fixation developed. When chloramphenicol was added to inhibit protein synthesis after 30min of supplemented post-UV incubation, at a time sufficient for expression of UV-induced protein(s), fixation of lethality or mutation was still annulled (no change in the effectiveness of PR developed). Lethality fixation did progress when protein synthesis was restricted and the cells were incubated in the presence of puromycin or were either clpP or clpX defective. We discuss these and related results to suggest (1) on-going protein synthesis is required in the fixation process for lethality and mutation to sustain an effective level of a hypothetical protein sensitive to ClpXP proteolysis and (2) this protein plays a critical role in the process leading to exchange between Pol III activity and alternative polymerase activities required as each cell deals with damage in template DNA.
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Affiliation(s)
- Amanda Burger
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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van den Boom V, Jaspers NGJ, Vermeulen W. When machines get stuck--obstructed RNA polymerase II: displacement, degradation or suicide. Bioessays 2002; 24:780-4. [PMID: 12210513 DOI: 10.1002/bies.10150] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The severe hereditary progeroid disorder Cockayne syndrome is a consequence of a defective transcription-coupled repair (TCR) pathway. This special mode of DNA repair aids a RNA polymerase that is stalled by a DNA lesion in the template and ensures efficient DNA repair to permit resumption of transcription and prevent cell death. Although some key players in TCR, such as the Cockayne syndrome A (CSA) and B (CSB) proteins have been identified, the exact molecular mechanism still remains illusive. A recent report provides new unexpected insights into TCR in yeast. The identification and characterisation of a novel protein co-purifying with the yeast homologue of CSB (Rad26) imposes reassessment of our current understanding of TCR in yeast. What about humans?
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Affiliation(s)
- Vincent van den Boom
- Department of Cell Biology and Genetics, Medical Genetic Center, Erasmus University Rotterdam, The Netherlands
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Deng J, Harding HP, Raught B, Gingras AC, Berlanga JJ, Scheuner D, Kaufman RJ, Ron D, Sonenberg N. Activation of GCN2 in UV-irradiated cells inhibits translation. Curr Biol 2002; 12:1279-86. [PMID: 12176355 DOI: 10.1016/s0960-9822(02)01037-0] [Citation(s) in RCA: 210] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
BACKGROUND Mammalian cells subjected to ultraviolet (UV) irradiation actively repress DNA replication, transcription, and mRNA translation. While the effects of UV irradiation on DNA replication and transcription have been extensively studied, the mechanism(s) responsible for translational repression are poorly understood. RESULTS Here, we demonstrate that UV irradiation elicits phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF2alpha) by activating the kinase GCN2 in a manner that does not require SAPK/JNK or p38 MAP kinase. GCN2-/- cells, and cells expressing nonphosphorylatable eIF2alpha as their only source of eIF2alpha protein, fail to repress translation in response to UV irradiation. CONCLUSIONS These results provide a mechanism for translation inhibition by UV irradiation and identify a hitherto unrecognized role for mammalian GCN2 as a mediator of the cellular response to UV stress.
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Affiliation(s)
- Jing Deng
- Department of Biochemistry and McGill Cancer Centre, McGill University, 3655 Promenade Sir William Osler, Montreal, H3G 1Y6, Quebec, Canada
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