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Macdonald Miller S, Abbriano RM, Herdean A, Banati R, Ralph PJ, Pernice M. Random mutagenesis of Phaeodactylum tricornutum using ultraviolet, chemical, and X-radiation demonstrates the need for temporal analysis of phenotype stability. Sci Rep 2023; 13:22385. [PMID: 38104215 PMCID: PMC10725415 DOI: 10.1038/s41598-023-45899-2] [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: 01/16/2023] [Accepted: 10/25/2023] [Indexed: 12/19/2023] Open
Abstract
We investigated two non-ionising mutagens in the form of ultraviolet radiation (UV) and ethyl methanosulfonate (EMS) and an ionising mutagen (X-ray) as methods to increase fucoxanthin content in the model diatom Phaeodactylum tricornutum. We implemented an ultra-high throughput method using fluorescence-activated cell sorting (FACS) and live culture spectral deconvolution for isolation and screening of potential pigment mutants, and assessed phenotype stability by measuring pigment content over 6 months using high-performance liquid chromatography (HPLC) to investigate the viability of long-term mutants. Both UV and EMS resulted in significantly higher fucoxanthin within the 6 month period after treatment, likely as a result of phenotype instability. A maximum fucoxanthin content of 135 ± 10% wild-type found in the EMS strain, a 35% increase. We found mutants generated using all methods underwent reversion to the wild-type phenotype within a 6 month time period. X-ray treatments produced a consistently unstable phenotype even at the maximum treatment of 1000 Grays, while a UV mutant and an EMS mutant reverted to wild-type after 4 months and 6 months, respectively, despite showing previously higher fucoxanthin than wild-type. This work provides new insights into key areas of microalgal biotechnology, by (i) demonstrating the use of an ionising mutagen (X-ray) on a biotechnologically relevant microalga, and by (ii) introducing temporal analysis of mutants which has substantial implications for strain creation and utility for industrial applications.
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Affiliation(s)
- Sean Macdonald Miller
- Faculty of Science, Climate Change Cluster (C3), University of Technology Sydney, Sydney, NSW, 2007, Australia.
| | - Raffaela M Abbriano
- Faculty of Science, Climate Change Cluster (C3), University of Technology Sydney, Sydney, NSW, 2007, Australia
| | - Andrei Herdean
- Faculty of Science, Climate Change Cluster (C3), University of Technology Sydney, Sydney, NSW, 2007, Australia
| | - Richard Banati
- Australian Nuclear Science and Technology Organisation (ANSTO), Kirrawee DC, NSW, 2232, Australia
- Faculty of Medicine and Health, University of Sydney, Camperdown, NSW, 2006, Australia
| | - Peter J Ralph
- Faculty of Science, Climate Change Cluster (C3), University of Technology Sydney, Sydney, NSW, 2007, Australia
| | - Mathieu Pernice
- Faculty of Science, Climate Change Cluster (C3), University of Technology Sydney, Sydney, NSW, 2007, Australia
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Du H, Pan B, Alund AW, Yan J, Chen Y, Robison TW, Chen T. Evaluation of mutagenic susceptibility of different stages in germ cell development of Caenorhabditis elegans using whole genome sequencing. Arch Toxicol 2023; 97:2261-2272. [PMID: 37209179 DOI: 10.1007/s00204-023-03526-z] [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: 03/20/2023] [Accepted: 05/11/2023] [Indexed: 05/22/2023]
Abstract
In contrast to somatic mutations, mutations in germ cells affect every cell of any organism derived from the germ cell and therefore are related to numerous genetic diseases. However, there is no suitable assay to evaluate the mutagenic sensitivities of both male and female germ cells. The main type of Caenorhabditis elegans (C. elegans) is hermaphroditic, where spermatogenesis and oogenesis occur chronologically at specific stages, allowing induction of mutations in either sperm or eggs exclusively. In this study, we used the alkylating agent ethyl methanesulfonate and N-ethyl-N-nitrosourea to induce germline mutations in C. elegans at different developmental stages and analyzed mutation frequency and mutational spectrum from data gathered using next-generation sequencing (NGS) technology. Our results revealed low spontaneous mutation rates of C. elegans, along with distinct mutagenic effects elicited by the two mutagens. Our data show that the parental worms treated during germ cell mitosis, spermatogenesis, and oogenesis resulted in different mutation frequencies in their offspring, and female germ cells could be very susceptible to mutagen exposure during oogenesis. In summary, our study indicates that the use of C. elegans and its specific chronological hermaphroditism would be a promising way to explore the sensitivities of both male and female germ cells to mutagens.
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Affiliation(s)
- Hua Du
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, 3900 NCTR Rd, Jefferson, AR, 72079, USA
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, 230031, Anhui, People's Republic of China
| | - Bohu Pan
- Division of Bioinformatics and Biostatistics, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, 72079, USA
| | - Alexander W Alund
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, 3900 NCTR Rd, Jefferson, AR, 72079, USA
- Discovery Sciences | Medicine Design, Pfizer Inc., 280 Shennecossett Rd, Groton, CT, 06340, USA
| | - Jian Yan
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, 3900 NCTR Rd, Jefferson, AR, 72079, USA
| | - Ying Chen
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, 3900 NCTR Rd, Jefferson, AR, 72079, USA
| | - Timothy W Robison
- Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, 20993, USA
| | - Tao Chen
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, 3900 NCTR Rd, Jefferson, AR, 72079, USA.
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3
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El Mir J, Fedou S, Thézé N, Morice-Picard F, Cario M, Fayyad-Kazan H, Thiébaud P, Rezvani HR. Xenopus: An in vivo model for studying skin response to ultraviolet B irradiation. Dev Growth Differ 2023; 65:194-202. [PMID: 36880984 DOI: 10.1111/dgd.12848] [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: 05/28/2022] [Revised: 02/25/2023] [Accepted: 02/27/2023] [Indexed: 03/08/2023]
Abstract
Ultraviolet B (UVB) in sunlight cause skin damage, ranging from wrinkles to photoaging and skin cancer. UVB can affect genomic DNA by creating cyclobutane pyrimidine dimers (CPDs) and pyrimidine-pyrimidine (6-4) photoproducts (6-4PPs). These lesions are mainly repaired by the nucleotide excision repair (NER) system and by photolyase enzymes that are activated by blue light. Our main goal was to validate the use of Xenopus laevis as an in vivo model system for investigating the impact of UVB on skin physiology. The mRNA expression levels of xpc and six other genes of the NER system and CPD/6-4PP photolyases were found at all stages of embryonic development and in all adult tissues tested. When examining Xenopus embryos at different time points after UVB irradiation, we observed a gradual decrease in CPD levels and an increased number of apoptotic cells, together with an epidermal thickening and an increased dendricity of melanocytes. We observed a quick removal of CPDs when embryos are exposed to blue light versus in the dark, confirming the efficient activation of photolyases. A decrease in the number of apoptotic cells and an accelerated return to normal proliferation rate was noted in blue light-exposed embryos compared with their control counterparts. Overall, a gradual decrease in CPD levels, detection of apoptotic cells, thickening of epidermis, and increased dendricity of melanocytes, emulate human skin responses to UVB and support Xenopus as an appropriate and alternative model for such studies.
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Affiliation(s)
- Joudi El Mir
- University Bordeaux, Inserm, BRIC, Bordeaux, France
| | | | - Nadine Thézé
- University Bordeaux, Inserm, BRIC, Bordeaux, France
| | - Fanny Morice-Picard
- University Bordeaux, Inserm, BRIC, Bordeaux, France.,Department of Dermatology and Pediatric Dermatology, National Reference Centre for Rare Disorders, Hôpital des Enfants Pellegrin, Centre Hospitalier Universitaire de Bordeaux, Bordeaux, France
| | - Muriel Cario
- University Bordeaux, Inserm, BRIC, Bordeaux, France.,Aquiderm, University of Bordeaux, Bordeaux, France
| | - Hussein Fayyad-Kazan
- Laboratory of Cancer Biology and Molecular Immunology, Faculty of Sciences I, Lebanese University, Hadath, Lebanon
| | | | - Hamid-Reza Rezvani
- University Bordeaux, Inserm, BRIC, Bordeaux, France.,Aquiderm, University of Bordeaux, Bordeaux, France
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Darré M, Vicente AR, Cisneros-Zevallos L, Artés-Hernández F. Postharvest Ultraviolet Radiation in Fruit and Vegetables: Applications and Factors Modulating Its Efficacy on Bioactive Compounds and Microbial Growth. Foods 2022; 11:foods11050653. [PMID: 35267286 PMCID: PMC8909097 DOI: 10.3390/foods11050653] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Revised: 02/07/2022] [Accepted: 02/07/2022] [Indexed: 12/17/2022] Open
Abstract
Ultraviolet (UV) radiation has been considered a deleterious agent that living organisms must avoid. However, many of the acclimation changes elicited by UV induce a wide range of positive effects in plant physiology through the elicitation of secondary antioxidant metabolites and natural defenses. Therefore, this fact has changed the original UV conception as a germicide and potentially damaging agent, leading to the concept that it is worthy of application in harvested commodities to take advantage of its beneficial responses. Four decades have already passed since postharvest UV radiation applications began to be studied. During this time, UV treatments have been successfully evaluated for different purposes, including the selection of raw materials, the control of postharvest diseases and human pathogens, the elicitation of nutraceutical compounds, the modulation of ripening and senescence, and the induction of cross-stress tolerance. Besides the microbicide use of UV radiation, the effect that has received most attention is the elicitation of bioactive compounds as a defense mechanism. UV treatments have been shown to induce the accumulation of phytochemicals, including ascorbic acid, carotenoids, glucosinolates, and, more frequently, phenolic compounds. The nature and extent of this elicitation have been reported to depend on several factors, including the product type, maturity, cultivar, UV spectral region, dose, intensity, and radiation exposure pattern. Even though in recent years we have greatly increased our understanding of UV technology, some major issues still need to be addressed. These include defining the operational conditions to maximize UV radiation efficacy, reducing treatment times, and ensuring even radiation exposure, especially under realistic processing conditions. This will make UV treatments move beyond their status as an emerging technology and boost their adoption by industry.
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Affiliation(s)
- Magalí Darré
- LIPA—Laboratorio de Investigación en Productos Agroindustriales, Universidad Nacional de La Plata, Calle 60 y 119 s/n, La Plata CP 1900, Argentina;
| | - Ariel Roberto Vicente
- LIPA—Laboratorio de Investigación en Productos Agroindustriales, Universidad Nacional de La Plata, Calle 60 y 119 s/n, La Plata CP 1900, Argentina;
- Correspondence:
| | - Luis Cisneros-Zevallos
- Department of Horticultural Sciences, Texas A&M University, College Station, TX 77843, USA;
| | - Francisco Artés-Hernández
- Postharvest and Refrigeration Group, Department of Agronomical Engineering & Institute of Plant Biotechnology, Universidad Politécnica de Cartagena, 30203 Murcia, Spain;
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Co-Occurrence of blaOXA-23 in the Chromosome and Plasmid: Increased Fitness in Carbapenem-Resistant Acinetobacter baumannii. Antibiotics (Basel) 2021; 10:antibiotics10101196. [PMID: 34680777 PMCID: PMC8532878 DOI: 10.3390/antibiotics10101196] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 09/20/2021] [Accepted: 09/23/2021] [Indexed: 11/17/2022] Open
Abstract
This study aims to explore the co-occurrence of chromosomal and plasmid blaOXA-23 in carbapenem-resistant A. baumannii (CRAB) and its influence on phenotypes. A total of 11 CRAB isolates containing copies of blaOXA-23 on the chromosome and plasmid (CO), as well as 18 closely related isolates with blaOXA-23, located on either the chromosome or plasmid (SI), were selected for the determination of antibiotic susceptibility, virulence phenotype, and characteristic genomic differences. The co-occurrence of blaOXA-23 on the CRAB chromosome and plasmids did not enhance carbapenem resistance, but trimethoprim/sulfamethoxazole exhibited significantly reduced minimum inhibitory concentrations in CO. CO demonstrated a higher degree of fitness compared to SI. An increased biofilm formation ability and serum tolerance were also identified in CO, which may be associated with virulence genes, which include csuD, entE, pgaA, and plc. blaOXA-23-carrying transposons were found at different insertion sites on the chromosome. The most common site was AbaR-type genomic islands (50%). Two types of plasmids were found in CO. The co-occurrence of blaOXA-23 on the chromosome and a plasmid in CRAB had little effect on carbapenem susceptibility but was accompanied by increased fitness and virulence. Different origins and independent insertions of blaOXA-23-carrying transposons were identified in both the chromosomal and plasmid sequences.
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Chung LH, Murray V. An extended sequence specificity for UV-induced DNA damage. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2017; 178:133-142. [PMID: 29149689 DOI: 10.1016/j.jphotobiol.2017.10.034] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 10/26/2017] [Accepted: 10/28/2017] [Indexed: 01/26/2023]
Abstract
The sequence specificity of UV-induced DNA damage was determined with a higher precision and accuracy than previously reported. UV light induces two major damage adducts: cyclobutane pyrimidine dimers (CPDs) and pyrimidine(6-4)pyrimidone photoproducts (6-4PPs). Employing capillary electrophoresis with laser-induced fluorescence and taking advantages of the distinct properties of the CPDs and 6-4PPs, we studied the sequence specificity of UV-induced DNA damage in a purified DNA sequence using two approaches: end-labelling and a polymerase stop/linear amplification assay. A mitochondrial DNA sequence that contained a random nucleotide composition was employed as the target DNA sequence. With previous methodology, the UV sequence specificity was determined at a dinucleotide or trinucleotide level; however, in this paper, we have extended the UV sequence specificity to a hexanucleotide level. With the end-labelling technique (for 6-4PPs), the consensus sequence was found to be 5'-GCTC*AC (where C* is the breakage site); while with the linear amplification procedure, it was 5'-TCTT*AC. With end-labelling, the dinucleotide frequency of occurrence was highest for 5'-TC*, 5'-TT* and 5'-CC*; whereas it was 5'-TT* for linear amplification. The influence of neighbouring nucleotides on the degree of UV-induced DNA damage was also examined. The core sequences consisted of pyrimidine nucleotides 5'-CTC* and 5'-CTT* while an A at position "1" and C at position "2" enhanced UV-induced DNA damage.
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Affiliation(s)
- Long H Chung
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Vincent Murray
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
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How a Genetically Stable Extremophile Evolves: Modes of Genome Diversification in the Archaeon Sulfolobus acidocaldarius. J Bacteriol 2017. [PMID: 28630130 DOI: 10.1128/jb.00177-17] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In order to analyze in molecular terms how Sulfolobus genomes diverge, damage-induced mutations and natural polymorphisms (PMs) were identified in laboratory constructs and wild-type isolates, respectively, of Sulfolobus acidocaldarius Among wild-type isolates drawn from one local population, pairwise nucleotide divergence averaged 4 × 10-6, which is about 0.15% of the corresponding divergence reported for Sulfolobus islandicus The most variable features of wild-type S. acidocaldarius genomes were homopolymer (mononucleotide) tracts and longer tandem repeats, consistent with the spontaneous mutations that occur under laboratory conditions. Natural isolates, however, also revealed large insertions/deletions and inversions, which did not occur in any of the laboratory-manipulated strains. Several of the large insertions/deletions could be attributed to the integration or excision of mobile genetic elements (MGEs), and each MGE represented a distinct system of site-specific recombination. The mode of recombination associated with one MGE, a provirus related to Sulfolobus turreted icosahedral virus, was also seen in certain chromosomal inversions. Artificially induced mutations, non-MGE insertions/deletions, and small PMs exhibited different distributions over the genome, suggesting that large-scale patterning of Sulfolobus genomes begins early in the divergence process. Unlike induced mutations, natural base pair substitutions occurred in clusters, and one cluster exhibited properties expected of nonreciprocal recombination (gene conversion) between dispersed imperfect repeats. Taken together, the results identify simple replication errors, slipped-strand events promoted by tandem repeats, homologous recombination, and rearrangements promoted by MGEs as the primary sources of genetic variation for this extremely acidophilic archaeon in its geothermal environment.IMPORTANCE The optimal growth temperatures of hyperthermophilic archaea accelerate DNA decomposition, which is expected to make DNA repair especially important for their genetic stability, yet these archaea lack certain broadly conserved types of DNA repair proteins. In this study, the genome of the extreme thermoacidophile Sulfolobus acidocaldarius was found to be remarkably stable, accumulating few mutations in many (though not all) laboratory manipulations and in natural populations. Furthermore, all the genetic processes that were inferred to diversify these genomes also operate in mesophilic bacteria and eukaryotes. This suggests that a common set of mechanisms produces most of the genetic variation in all microorganisms, despite the fundamental differences in physiology, DNA repair systems, and genome structure represented in the three domains of life.
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Shriber P, Leitner-Dagan Y, Geacintov N, Paz-Elizur T, Livneh Z. DNA sequence context greatly affects the accuracy of bypass across an ultraviolet light 6-4 photoproduct in mammalian cells. Mutat Res 2015; 780:71-6. [PMID: 26302378 DOI: 10.1016/j.mrfmmm.2015.08.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 07/25/2015] [Accepted: 08/10/2015] [Indexed: 12/18/2022]
Abstract
Translesion DNA synthesis (TLS) is a DNA damage tolerance mechanism carried out by low-fidelity DNA polymerases that bypass DNA lesions, which overcomes replication stalling. Despite the miscoding nature of most common DNA lesions, several of them are bypassed in mammalian cells in a relatively accurate manner, which plays a key role maintaining a low mutation load. Whereas it is generally agreed that TLS across the major UV and sunlight induced DNA lesion, the cyclobutane pyrimidine dimer (CPD), is accurate, there were conflicting reports on whether the same is true for the thymine-thymine pyrimidine-pyrimidone(6-4) ultraviolet light photoproduct (TT6-4PP), which represents the second most common class of UV lesions. Using a TLS assay system based on gapped plasmids carrying site-specific TT6-4PP lesions in defined sequence contexts we show that the DNA sequence context markedly affected both the extent and accuracy of TLS. The sequence exhibiting higher TLS exhibited also higher error-frequency, caused primarily by semi-targeted mutations, at the nearest nucleotides flanking the lesion. Our results resolve the discrepancy reported on TLS across TT6-4PP, and suggest that TLS is more accurate in human cells than in mouse cells.
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Affiliation(s)
- Pola Shriber
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Yael Leitner-Dagan
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel
| | | | - Tamar Paz-Elizur
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel.
| | - Zvi Livneh
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel.
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Multiple strategies for translesion synthesis in bacteria. Cells 2012; 1:799-831. [PMID: 24710531 PMCID: PMC3901139 DOI: 10.3390/cells1040799] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 09/29/2012] [Accepted: 09/30/2012] [Indexed: 12/16/2022] Open
Abstract
Damage to DNA is common and can arise from numerous environmental and endogenous sources. In response to ubiquitous DNA damage, Y-family DNA polymerases are induced by the SOS response and are capable of bypassing DNA lesions. In Escherichia coli, these Y-family polymerases are DinB and UmuC, whose activities are modulated by their interaction with the polymerase manager protein UmuD. Many, but not all, bacteria utilize DinB and UmuC homologs. Recently, a C-family polymerase named ImuC, which is similar in primary structure to the replicative DNA polymerase DnaE, was found to be able to copy damaged DNA and either carry out or suppress mutagenesis. ImuC is often found with proteins ImuA and ImuB, the latter of which is similar to Y‑family polymerases, but seems to lack the catalytic residues necessary for polymerase activity. This imuAimuBimuC mutagenesis cassette represents a widespread alternative strategy for translesion synthesis and mutagenesis in bacteria. Bacterial Y‑family and ImuC DNA polymerases contribute to replication past DNA damage and the acquisition of antibiotic resistance.
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Izhar L, Goldsmith M, Dahan R, Geacintov N, Lloyd RG, Livneh Z. Analysis of strand transfer and template switching mechanisms of DNA gap repair by homologous recombination in Escherichia coli: predominance of strand transfer. J Mol Biol 2008; 381:803-9. [PMID: 18585391 DOI: 10.1016/j.jmb.2008.06.031] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Revised: 06/04/2008] [Accepted: 06/11/2008] [Indexed: 10/21/2022]
Abstract
Daughter strand gaps formed upon interruption of replication at DNA lesions in Escherichia coli can be repaired by either translesion DNA synthesis or homologous recombination (HR) repair. Using a plasmid-based assay system that enables discrimination between strand transfer and template switching (information copying) modes of HR gap repair, we found that approximately 80% of strand gaps were repaired by physical strand transfer from the donor, whereas approximately 20% appear to be repaired by template switching. HR gap repair operated on both small and bulky lesions and largely depended on RecA and RecF but not on the RecBCD nuclease. In addition, we found that HR was mildly reduced in cells lacking the RuvABC and RecG proteins involved in resolution of Holliday junctions. These results, obtained for the first time under conditions that detect the two HR gap repair mechanisms, provide in vivo high-resolution molecular evidence for the predominance of the strand transfer mechanism in HR gap repair. A small but significant portion of HR gap repair appears to occur via a template switching mechanism.
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Affiliation(s)
- Lior Izhar
- Department of Biological Chemistry, Faculty of Biochemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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11
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Abstract
All organisms possess a diverse set of genetic programs that are used to alter cellular physiology in response to environmental cues. The gram-negative bacterium, Escherichia coli, mounts what is known as the "SOS response" following DNA damage, replication fork arrest, and a myriad of other environmental stresses. For over 50 years, E. coli has served as the paradigm for our understanding of the transcriptional, and physiological changes that occur following DNA damage (400). In this chapter, we summarize the current view of the SOS response and discuss how this genetic circuit is regulated. In addition to examining the E. coli SOS response, we also include a discussion of the SOS regulatory networks in other bacteria to provide a broader perspective on how prokaryotes respond to DNA damage.
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Liu W, Yang YS, Zhou Q, Xie L, Li P, Sun T. Impact assessment of cadmium contamination on rice (Oryza sativa L.) seedlings at molecular and population levels using multiple biomarkers. CHEMOSPHERE 2007; 67:1155-63. [PMID: 17184821 DOI: 10.1016/j.chemosphere.2006.11.011] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2006] [Revised: 11/07/2006] [Accepted: 11/09/2006] [Indexed: 05/13/2023]
Abstract
Assessment of environmental contamination on ecology (plant) at molecular and population levels is important in risk quantification and remediation study. Random amplified polymorphic DNA (RAPD) assay and related other fingerprinting techniques have been employed to detect the genotoxin-induced DNA damage and mutations. This research compared the effects occurring at molecular and population levels in rice seedlings exposed to cadmium (Cd) concentrations of 15-60 mg l(-1) for 8 days with quartz sand culture. Inhibition of root growth and increase of total soluble protein content in root tips of rice seedlings were observed with the increase of Cd concentration. For the RAPD analyses, 12 RAPD primers of 50-70% GC content were found to produce unique polymorphic band patterns and subsequently were used to produce a total of 180 bands of 179-3056 bp in molecular size in the control root tips of rice seedlings. Results produced by these RAPD primers indicate that changes in RAPD profiles of root tips after Cd treatment include modifications in band intensity and gain or loss of bands by comparison with control. The effect of changes was dose-dependent. Genomic template stability compares favourably with the traditional indices such as root growth and soluble protein content. The DNA polymorphisms detected by RAPD analysis can be applied as a suitable biomarker assay for the detection of genotoxic effects of Cd contamination on plants.
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Affiliation(s)
- Wan Liu
- Key laboratory of Terrestrial Ecological Processes, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, PR China
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15
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Atienzar FA, Jha AN. The random amplified polymorphic DNA (RAPD) assay and related techniques applied to genotoxicity and carcinogenesis studies: a critical review. Mutat Res 2006; 613:76-102. [PMID: 16979375 DOI: 10.1016/j.mrrev.2006.06.001] [Citation(s) in RCA: 165] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2006] [Revised: 06/12/2006] [Accepted: 06/12/2006] [Indexed: 01/01/2023]
Abstract
More than 9000 papers using the random amplified polymorphic DNA (RAPD) or related techniques (e.g. the arbitrarily primed polymerase chain reaction (AP-PCR)) have been published from 1990 to 2005. The RAPD method has been initially used to detect polymorphism in genetic mapping, taxonomy and phylogenetic studies and later in genotoxicity and carcinogenesis studies. Despite their extensive use, these techniques have also attracted some criticisms, mainly for lack of reproducibility. In the light of their widespread applications, the objectives of this review are to (1) identify the potential factors affecting the optimisation of the RAPD and AP-PCR assays, (2) critically describe and analyse these techniques in genotoxicity and carcinogenesis studies, (3) compare the RAPD assay with other well used methodologies, (4) further elucidate the impact of DNA damage and mutations on the RAPD profiles, and finally (5) provide some recommendations/guidelines to further improve the applications of the assays and to help the identification of the factors responsible for the RAPD changes. It is suggested that after proper optimisation, the RAPD is a reliable, sensitive and reproducible assay, has the potential to detect a wide range of DNA damage (e.g. DNA adducts, DNA breakage) as well as mutations (point mutations and large rearrangements) and therefore can be applied to genotoxicity and carcinogenesis studies. Nevertheless, the interpretation of the changes in RAPD profiles is difficult since many factors can affect the generation of RAPD profiles. It is therefore important that these factors are identified and taken into account while using these assays. On the other hand, further analyses of the relevant bands generated in RAPD profile allow not only to identify some of the molecular events implicated in the genomic instability but also to discover genes playing key roles, particularly in the initiation and development of malignancy. Finally, to elucidate the potential genotoxic effects of environmental contaminants, a powerful strategy could be firstly to use the RAPD assay as a screening method and secondly to apply more specific methods measuring for instance DNA adducts, gene mutations or cytogenetic effects. It is also envisaged that these assays (i.e. RAPD and related techniques), which reflect effects at whole genome level, would continue to complement the use of emerging technologies (e.g. microarrays which aim to quantify expression of individual genes).
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Affiliation(s)
- Franck A Atienzar
- School of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, Devon, UK.
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Adar S, Livneh Z. Translesion DNA synthesis across non-DNA segments in cultured human cells. DNA Repair (Amst) 2006; 5:479-90. [PMID: 16473566 DOI: 10.1016/j.dnarep.2006.01.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Revised: 01/05/2006] [Accepted: 01/09/2006] [Indexed: 11/17/2022]
Abstract
DNA lesions that have escaped DNA repair are tolerated via translesion DNA synthesis (TLS), carried out by specialized error-prone DNA polymerases. To evaluate the robustness of the TLS system in human cells, we examined its ability to cope with foreign non-DNA stretches of 3 or 12 methylene residues, using a gap-lesion plasmid assay system. We found that both the trimethylene and dodecamethylene inserts were bypassed with significant efficiencies in human cells, using both misinsertion and misalignment mechanisms. TLS across these non-DNA segments was aphidicolin-sensitive, and did not require poleta. In vitro primer extension assays showed that purified poleta, polkappa and poliota were each capable of inserting each of the four nucleotides opposite the trimethylene chain, but only poleta and polkappa could fully bypass it. Poleta and poliota, but not polkappa, could also insert each of the four nucleotides opposite the dodecamethylene chain, but all three polymerases were severely blocked by this lesion. The ability of TLS polymerases to insert nucleotides opposite a hydrocarbon chain, despite the lack of any similarity to DNA, suggests that they may act via a mode of transient and local template-independent polymerase activity, and highlights the robustness of the TLS system in human cells.
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Affiliation(s)
- Sheera Adar
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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17
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Abstract
The processes of DNA replication and recombination are intertwined at many different levels. In diverse systems, extensive DNA replication can be triggered by genetic recombination, with assembly of a replication complex onto a D-loop recombination intermediate. This and related pathways of replisome assembly allow the completion of DNA replication when forks initiated at a conventional replication origin fail before completing replication of the genome. In addition, the repair of double-strand breaks or gaps by homologous recombination requires at least limited DNA replication to replace the missing information. An intricate interplay between replication and recombination is also evident during the termination of bacterial DNA replication and during the induction of the bacterial SOS response to DNA damage.
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Affiliation(s)
- Kenneth N Kreuzer
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA.
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18
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Abstract
Skin cancer is a large and growing problem in the United States. Sun and other ultraviolet (UV) light exposures play a key role in the development of skin cancer. Pediatricians can play an important role in counseling patients and are in a position to help educate children and their families about skin cancer. The purpose of this review is to familiarize pediatricians with the magnitude of the skin cancer problem and the evidence that ultraviolet light exposure, particularly indoor tanning, contributes to this problem. We reviewed the literature on ultraviolet light and skin cancer (based on a MEDLINE search of articles using the headings "ultraviolet light" and "skin cancer") and found that skin cancer is the most rapidly growing cause of cancer deaths in the United State. There is strong epidemiologic evidence for the relationship between UV exposure and nonmelanoma skin cancer and growing evidence for the relationship between indoor tanning and melanoma. We recommend that pediatricians counsel children and their parents about UV protection. Measures such as use of sunscreen and hats for outdoor play, both at home and in school, should be encouraged.
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Affiliation(s)
- Farah R Abdulla
- Center for Dermatology Research, Department of Dermatology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1071, USA
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19
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Galhardo RS, Rocha RP, Marques MV, Menck CFM. An SOS-regulated operon involved in damage-inducible mutagenesis in Caulobacter crescentus. Nucleic Acids Res 2005; 33:2603-14. [PMID: 15886391 PMCID: PMC1092274 DOI: 10.1093/nar/gki551] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
DNA polymerases of the Y-family, such as Escherichia coli UmuC and DinB, are specialized enzymes induced by the SOS response, which bypass lesions allowing the continuation of DNA replication. umuDC orthologs are absent in Caulobacter crescentus and other bacteria, raising the question about the existence of SOS mutagenesis in these organisms. Here, we report that the C.crescentus dinB ortholog is not involved in damage-induced mutagenesis. However, an operon composed of two hypothetical genes and dnaE2, encoding a second copy of the catalytic subunit of Pol III, is damage inducible in a recA-dependent manner, and is responsible for most ultraviolet (UV) and mitomycin C-induced mutations in C.crescentus. The results demonstrate that the three genes are required for the error-prone processing of DNA lesions. The two hypothetical genes were named imuA and imuB, after inducible mutagenesis. ImuB is similar to proteins of the Y-family of polymerases, and possibly cooperates with DnaE2 in lesion bypass. The mutations arising as a consequence of the activity of the imuAB dnaE2 operon are rather unusual for UV irradiation, including G:C to C:G transversions.
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Affiliation(s)
| | | | | | - Carlos F. M. Menck
- To whom correspondence should be addressed at Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, Avenue Professor Lineu Prestes, 1374, São Paulo, SP 05508-900, Brazil. Tel: +55 11 3091 7499; Fax: +55 11 3091 7354;
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20
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Avkin S, Goldsmith M, Velasco-Miguel S, Geacintov N, Friedberg EC, Livneh Z. Quantitative analysis of translesion DNA synthesis across a benzo[a]pyrene-guanine adduct in mammalian cells: the role of DNA polymerase kappa. J Biol Chem 2004; 279:53298-305. [PMID: 15475561 DOI: 10.1074/jbc.m409155200] [Citation(s) in RCA: 153] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Replication across unrepaired DNA lesions in mammalian cells is effected primarily by specialized, low fidelity DNA polymerases. We studied translesion DNA synthesis (TLS) across a benzo[a]pyrene-guanine (BP-G) adduct, a major mutagenic DNA lesion generated by tobacco smoke. This was done using a quantitative assay that measures TLS indirectly, by measuring the recovery of gapped plasmids transfected into cultured mammalian cells. Analysis of PolK(+/+) mouse embryo fibroblasts (MEFs) showed that TLS across the BP-G adduct occurred with an efficiency of 48 +/- 4%, which is an order of magnitude higher than in Escherichia coli. In PolK(-/-) MEFs, bypass was 16 +/- 1%, suggesting that at least two-thirds of the BP-G adducts in MEFs were bypassed exclusively by polymerase kappa (polkappa). In contrast, poleta was not required for bypass across BP-G in a human XP-V cell line. Analysis of misinsertion specificity across BP-G revealed that bypass was more error-prone in MEFs lacking polkappa. Expression of polkappa from a plasmid introduced into PolK(-/-) MEFs restored both the extent and fidelity of bypass across BP-G. Polkappa was not required for bypass of a synthetic abasic site. In vitro analysis demonstrated efficient bypass across BP-G by both polkappa and poleta, suggesting that the biological role of polkappa in TLS across BP-G is due to regulation of TLS and not due to an exclusive ability to bypass this lesion. These results indicate that BP-G is bypassed in mammalian cells with relatively high efficiency and that polkappa bypasses BP-G in vivo with higher efficiency and higher accuracy than other DNA polymerases.
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Affiliation(s)
- Sharon Avkin
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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21
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Zhang S, Sundin GW. Long-term effect of mutagenic DNA repair on accumulation of mutations in Pseudomonas syringae B86-17. J Bacteriol 2004; 186:7807-10. [PMID: 15516596 PMCID: PMC524919 DOI: 10.1128/jb.186.22.7807-7810.2004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2004] [Accepted: 08/12/2004] [Indexed: 11/20/2022] Open
Abstract
Forty replicate lineages of Pseudomonas syringae B86-17 cells expressing the rulAB mutagenic DNA repair (MDR) determinant or the rulB::Km MDR-deficient mutant GWS242 were passaged through single-cell bottlenecks (60 cycles), with a UV radiation (UVR) exposure given to half of the lineages at the beginning of each cycle. After every 10th bottleneck cycle, single-colony isolates from all 80 lineages were subjected to 39 phenotypic screens, with newly arising mutations detected in 60 and 0% of UVR-exposed or non-UVR-exposed B86-17 lineages, respectively, by the 60th cycle. Cellular fitness, measured as growth rate in a minimal medium, of UVR-exposed lineages of both B86-17 and GWS242 after 60 cycles was not significantly different from that of the ancestral strains. Although UVR exposure and MDR activity increased the occurrence of mutations in cells, a significant reduction in overall fitness was not observed.
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Affiliation(s)
- Shouan Zhang
- National Center for Agricultural Utilization Research, USDA Agricultural Research Service, Peoria, Illinois, USA
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22
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Maor-Shoshani A, Ben-Ari V, Livneh Z. Lesion bypass DNA polymerases replicate across non-DNA segments. Proc Natl Acad Sci U S A 2003; 100:14760-5. [PMID: 14657386 PMCID: PMC299799 DOI: 10.1073/pnas.2433503100] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A critical feature of the robustness of the DNA replication machinery is the ability to complete its task in the presence of interfering DNA damage. A key mechanism responsible for this task is translesion replication (also termed translesion synthesis), carried out by specialized lesion bypass DNA polymerases of the Y superfamily. Here we show that in Escherichia coli, plasmids can be replicated across a segment of foreign non-DNA material, consisting of hydrocarbon chains of 3 or 12 methylene residues. This replication is carried out by DNA polymerase V and proceeds by at least two mechanisms: (i) Editing out the foreign insert, by polymerase "hopping" across it, which can be mediated by looping out of the insert, leading to its deletion, while preserving the DNA sequence. (ii) DNA synthesis through the insert, which occurs by incorporating one or two nucleotides opposite the hydrocarbon chain, yielding a net increase in the length of the DNA sequence. The remarkable ability of DNA polymerase V to insert nucleotides opposite a hydrocarbon chain shows that DNA synthesis can occur in a region of the template strand, which lacks all fundamental features of DNA, including its purine, pyrimidine, sugar, and phosphate moieties, and its hydrophilic and ionic nature. This bypass ability reflects a striking robustness of the translesion replication apparatus and is likely to contribute to its effectiveness in maintaining genome stability.
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Affiliation(s)
- Ayelet Maor-Shoshani
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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23
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Maor-Shoshani A, Livneh Z. Analysis of the stimulation of DNA polymerase V of Escherichia coli by processivity proteins. Biochemistry 2002; 41:14438-46. [PMID: 12450411 DOI: 10.1021/bi0262909] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Bypass of replication-blocking lesions in Escherichia coli is carried out by DNA polymerase V (UmuC) in a reaction that requires UmuD', RecA, and single-strand DNA-binding protein (SSB). The activity of this four-component basic bypass system is a low-fidelity and low-processivity activity. Addition of the processivity subunits of pol III, the beta subunit sliding DNA clamp, and the five-subunit gamma complex clamp loader increased the rate of translesion replication approximately 3-fold. This stimulation was specific to the lesion bypass step, with no effect on the initiation of synthesis by pol V. The beta subunit and gamma complex increased the processivity of pol V from 3 to approximately 14-18 nucleotides, providing a mechanistic basis for their stimulatory effect. Stimulation of bypass was observed over a range of RecA and SSB concentrations. ATPgammaS, which strongly inhibits translesion replication by pol V, primarily via inhibition of the initiation stage, caused the same inhibition also in the presence of the processivity proteins. The in vivo role of the processivity proteins in translesion replication was examined by assaying UV mutagenesis. This was done in a strain carrying the dnaN59 allele, encoding a temperature-sensitive beta subunit. When assayed in an excision repair-defective background, the dnaN59 mutant exhibited a level of UV mutagenesis reduced up to 3-fold compared to that of the isogenic dnaN(+) strain. This suggests that like in the in vitro system, the beta subunit stimulates lesion bypass in vivo.
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Affiliation(s)
- Ayelet Maor-Shoshani
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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24
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Berdichevsky A, Izhar L, Livneh Z. Error-free recombinational repair predominates over mutagenic translesion replication in E. coli. Mol Cell 2002; 10:917-24. [PMID: 12419234 DOI: 10.1016/s1097-2765(02)00679-2] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Tolerance mechanisms are important in the ability of cells to cope with DNA damage. In E. coli, the two main damage tolerance mechanisms are recombinational repair (RR) and translesion replication (TLR). Here we show that RR effectively repairs gaps opposite DNA lesions. When both mechanisms are functional, RR predominates over TLR, being responsible for 86% of the repair events. This predominance of RR is determined by the high concentration of RecA present under SOS conditions, which causes a differential inhibition of TLR. Further inhibition of TLR is caused by the RecA-catalyzed strand exchange reaction of RR. This molecular hierarchy in the tolerance of DNA lesions ensures that the nonmutagenic RR predominates over the mutagenic TLR, thereby contributing to genetic stability.
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Affiliation(s)
- Ala Berdichevsky
- Department of Biological Chemistry, The Weizmann Institute of Science, 76100, Rehovot, Israel
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25
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Diedrich MJ, Warters RL, Grossman D. Amifostine aminothiols and protection of keratinocyte apoptosis and DNA damage. J Invest Dermatol 2002; 119:707-8. [PMID: 12230519 DOI: 10.1046/j.1523-1747.2002.00213.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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26
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Miturski R, Bogusiewicz M, Ciotta C, Bignami M, Gogacz M, Burnouf D. Mismatch repair genes and microsatellite instability as molecular markers for gynecological cancer detection. Exp Biol Med (Maywood) 2002; 227:579-86. [PMID: 12192099 DOI: 10.1177/153537020222700805] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Due to major developments in genetics over the past decade, molecular biology tests are serving promising tools in early diagnosis and follow-up of cancer patients. Recent epidemiological studies revealed that the risk for each individual to develop cancer is closely linked to his/her own genetic potentialities. Some populations that are defective in DNA repair processes, for example in Xeroderma pigmentosum or in the Lynch syndrome, are particularly prone to cancer due to the accumulation of mutations within the genome. Such populations would benefit from the development of tests aimed at identifying people who are particularly at risk. Here, we review some data suggesting that the inactivation of mismatch repair is often found in endometrial cancer and we discuss molecular-based strategies that would help to identify the affected individuals in families with cases of glandular malignancies.
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Affiliation(s)
- Roman Miturski
- Second Department of Gynecological Surgery, University School of Medicine, Lublin, Poland.
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27
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Atienzar FA, Billinghurst Z, Depledge MH. 4-n-Nonylphenol and 17-beta estradiol may induce common DNA effects in developing barnacle larvae. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2002; 120:735-738. [PMID: 12442797 DOI: 10.1016/s0269-7491(02)00184-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
There is a growing concern over the potential effects of environmental endocrine disrupters on both human and wildlife populations. However, to date, minimal research has been conducted to determine the effect of estrogens and xenoestrogens at the DNA level. In this study, we used the random amplified polymorphic DNA (RAPD) assay to evaluate the effects on the genomic DNA of barnacle larvae that had been exposed to 17beta-estradiol (E2) and low concentrations of 4-n-nonylphenol (NP). DNA effects include DNA damage as well as mutations and possibly other effects at the DNA level that can be induced by chemical or physical agents that directly and/or indirectly interact with genomic DNA. Not only did exposure to NP and E2 induce changes in RAPD profiles in the exposed barnacle larvae when compared to control patterns, but also, and more importantly, there were similarities in the RAPD modifications in the exposed populations that had been treated to either chemical. We propose that NP and E2 induced some common DNA effects in barnacle larvae and that these specific modifications in RAPD patterns may arise as a consequence of hot spot DNA damage (e.g. DNA adducts) and/or mutations (point mutations or genomic rearrangements). This could help to explain how xenoestrogens mimic the effects produced by natural estrogens. In conclusion, in the field of endocrine disruption, the study of DNA effects induced by estrogens and/or xenoestrogens warrants further investigation. Indeed, changes at the DNA levcl may be the precursors of some of the numerous effects reported at higher levels of biological organisation such as the feminization of males, developmental abnormalities, and infertility.
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Affiliation(s)
- Franck A Atienzar
- Plymouth Environmental Research Centre, University of Plymouth, Devon, UK.
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28
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Lambert IB, Carroll C, Laycock N, Koziarz J, Lawford I, Duval L, Turner G, Booth R, Douville S, Whiteway J, Nokhbeh MR. Cellular determinants of the mutational specificity of 1-nitroso-6-nitropyrene and 1-nitroso-8-nitropyrene in the lacI gene of Escherichia coli. Mutat Res 2001; 484:19-48. [PMID: 11733069 DOI: 10.1016/s0027-5107(01)00234-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We have characterized 202 lacI(-) mutations, and 158 dominant lacI(-d) mutations following treatment of Escherichia coli strains NR6112 and EE125 with 1-nitroso-6-nitropyrene (1,6-NONP), an activated metabolite of the carcinogen 1,6-dinitropyrene. In all, 91% of the induced point mutations occurred at G:C residues. The -(G:C) frameshifts were the dominant mutational class in the lacI(-) collections of both NR6112 and EE125, and in the lacI(-d) collection of NR6112. Frameshift mutations occurred preferentially in runs of guanine residues, and their frequency increased with the length of the reiterated sequence. In strain EE125, which contained the plasmid pKM101, there was a marked stimulation in the frequency of base substitution mutations that was particularly apparent in the lacI(-d) collection. This study completes a comprehensive analysis of 1194 lacI(-) and 348 lacI(-d) mutations induced by either 1,6-NONP or its positional isomer 1-nitroso-8-nitropyrene (1,8-NONP) in strains of E. coli that differ with regard to their ability to carry out nucleotide excision repair and/or their ability to express the translesion synthesis DNA polymerase RI (MucAB) encoded by plasmid pKM101. Among the mutations are 763 frameshift mutations, 367 base substitutions and 47 deletions; these mutations have been characterized at more than 300 distinct sites in the lacI gene. Our studies provide detailed insight into the DNA sequence alterations and mutational mechanisms associated with dinitropyrene mutagenesis. We review the mutational spectra, and discuss cellular lesion repair or tolerance mechanisms that modulate the observed mutational specificity.
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Affiliation(s)
- I B Lambert
- Biology Department, Carleton University, 1125 Colonel By Drive, Ont., K1S 5B6, Ottawa, Canada.
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29
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Livneh Z. DNA damage control by novel DNA polymerases: translesion replication and mutagenesis. J Biol Chem 2001; 276:25639-42. [PMID: 11371576 DOI: 10.1074/jbc.r100019200] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Z Livneh
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
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30
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Affiliation(s)
- M M Bagheri
- Department of Dermatology, New York Medical College, Valhalla, New York 10595, USA
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31
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Affiliation(s)
- M A Horn
- Department of Dermatology, Northwestern University, 303 E. Superior Street, Chicago, IL 60611, USA
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32
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Reuven NB, Arad G, Stasiak AZ, Stasiak A, Livneh Z. Lesion bypass by the Escherichia coli DNA polymerase V requires assembly of a RecA nucleoprotein filament. J Biol Chem 2001; 276:5511-7. [PMID: 11084028 DOI: 10.1074/jbc.m006828200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Translesion replication is carried out in Escherichia coli by the SOS-inducible DNA polymerase V (UmuC), an error-prone polymerase, which is specialized for replicating through lesions in DNA, leading to the formation of mutations. Lesion bypass by pol V requires the SOS-regulated proteins UmuD' and RecA and the single-strand DNA-binding protein (SSB). Using an in vitro assay system for translesion replication based on a gapped plasmid carrying a site-specific synthetic abasic site, we show that the assembly of a RecA nucleoprotein filament is required for lesion bypass by pol V. This is based on the reaction requirements for stoichiometric amounts of RecA and for single-stranded gaps longer than 100 nucleotides and on direct visualization of RecA-DNA filaments by electron microscopy. SSB is likely to facilitate the assembly of the RecA nucleoprotein filament; however, it has at least one additional role in lesion bypass. ATPgammaS, which is known to strongly increase binding of RecA to DNA, caused a drastic inhibition of pol V activity. Lesion bypass does not require stoichiometric binding of UmuD' along RecA filaments. In summary, the RecA nucleoprotein filament, previously known to be required for SOS induction and homologous recombination, is also a critical intermediate in translesion replication.
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Affiliation(s)
- N B Reuven
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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33
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Ratner D, Peacocke M, Zhang H, Ping XL, Tsou HC. UV-specific p53 and PTCH mutations in sporadic basal cell carcinoma of sun-exposed skin. J Am Acad Dermatol 2001; 44:293-7. [PMID: 11174390 DOI: 10.1067/mjd.2001.112361] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
UVB irradiation is known to produce DNA damage at mutation hotspots in the p53 tumor suppressor gene, leading to the development of skin cancers. Mutations in the PTCH tumor suppressor gene, which is known to be responsible for the development of nevoid basal cell carcinoma syndrome, have also been identified in sporadic basal cell carcinomas (BCCs). We describe the case of an 80-year-old welder in whom 3 novel p53 mutations, as well as UV-specific PTCH mutations, were detected in two BCC samples from sun-exposed skin. The simultaneous presence of UV-specific p53 and PTCH mutations in the same BCC sample has not previously been reported.
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Affiliation(s)
- D Ratner
- Department of Dermatology, College of Physicians and Surgeons of Columbia University, New York, Ny, USA.
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34
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Goldsmith M, Sarov-Blat L, Livneh Z. Plasmid-encoded MucB protein is a DNA polymerase (pol RI) specialized for lesion bypass in the presence of MucA', RecA, and SSB. Proc Natl Acad Sci U S A 2000; 97:11227-31. [PMID: 11016960 PMCID: PMC17182 DOI: 10.1073/pnas.200361997] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Replication through damaged sites in DNA requires in Escherichia coli the SOS stress-inducible DNA polymerase V (UmuC), which is specialized for lesion bypass. Homologs of the umuC gene were found on native conjugative plasmids, which often carry multiple antibiotic-resistant genes. MucB is a UmuC homolog present on plasmid R46, and its variant plasmid pKM101 has been introduced into Salmonella strains for use in the Ames test for mutagens. Using a translesion replication assay based on a gapped plasmid carrying a site-specific synthetic abasic site in the single-stranded DNA region, we show that MucB is a DNA polymerase, termed pol RI, which is specialized for lesion bypass. The activity of pol RI requires the plasmid-encoded MucA' protein and the E. coli RecA and single-strand DNA binding proteins. Elimination of any of the proteins from the reaction abolished lesion bypass and polymerase activity. The unprocessed MucA could not substitute for MucA' in the bypass reaction. The presence of a lesion bypass DNA polymerase on a native conjugative plasmid, which has a broad host range specificity and carries multiple antibiotic-resistant genes, raises the possibility that mutagenesis caused by pol RI plays a role in the spreading of antibiotic resistance among bacterial pathogens.
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Affiliation(s)
- M Goldsmith
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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35
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Atienzar FA, Cordi B, Donkin ME, Evenden AJ, Jha AN, Depledge MH. Comparison of ultraviolet-induced genotoxicity detected by random amplified polymorphic DNA with chlorophyll fluorescence and growth in a marine macroalgae, Palmaria palmata. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2000; 50:1-12. [PMID: 10930646 DOI: 10.1016/s0166-445x(99)00100-9] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The random amplified polymorphic DNA (RAPD) technique was used to detect DNA damage in the sublittoral macroalgae Palmaria palmata (Rhodophyta) exposed to both ambient and elevated irradiances of UV-B (280-315 nm). To investigate the potential of this method in ecotoxicological assessments, the qualitative and quantitative modifications in RAPD profiles were compared with changes in a number of physiological and fitness parameters. RAPD detectable modifications in DNA profiles were observed in all UV exposed individuals compared with controls. Changes in chlorophyll fluorescence (F(v)/F(m) ratio), in vivo pigment absorptance, thallus growth and RAPD profiles, examined simultaneously, provided a sensitive measure of UV-induced toxicity. In conclusion, the application of the RAPD method in conjunction with other suitable physiological and fitness measurements, may prove to be a valuable tool for investigating the specific effects of genotoxic agents upon marine algal populations. Ultimately, this methodology may allow the ecotoxicological examination of the link between molecular alterations and measurable adverse effects at higher levels of biological organisation.
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Affiliation(s)
- FA Atienzar
- Department of Biological Sciences, Plymouth Environmental Research Centre (PERC), University of Plymouth, Drake Circus, Plymouth, PL4 8AA, Devon, UK
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36
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Maor-Shoshani A, Reuven NB, Tomer G, Livneh Z. Highly mutagenic replication by DNA polymerase V (UmuC) provides a mechanistic basis for SOS untargeted mutagenesis. Proc Natl Acad Sci U S A 2000; 97:565-70. [PMID: 10639119 PMCID: PMC15370 DOI: 10.1073/pnas.97.2.565] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
When challenged by DNA-damaging agents, Escherichia coli cells respond by inducing the SOS stress response, which leads to an increase in mutation frequency by two mechanisms: translesion replication, a process that causes mutations because of misinsertion opposite the lesions, and an inducible mutator activity, which acts at undamaged sites. Here we report that DNA polymerase V (pol V; UmuC), which previously has been shown to be a lesion-bypass DNA polymerase, was highly mutagenic during in vitro gap-filling replication of a gapped plasmid carrying the cro reporter gene. This reaction required, in addition to pol V, UmuD', RecA, and single-stranded DNA (ssDNA)-binding protein. pol V produced point mutations at a frequency of 2.1 x 10(-4) per nucleotide (2.1% per cro gene), 41-fold higher than DNA polymerase III holoenzyme. The mutational spectrum of pol V was dominated by transversions (53%), which were formed at a frequency of 1.3 x 10(-4) per nucleotide (1. 1% per cro gene), 74-fold higher than with pol III holoenzyme. The prevalence of transversions and the protein requirements of this system are similar to those of in vivo untargeted mutagenesis (SOS mutator activity). This finding suggests that replication by pol V, in the presence of UmuD', RecA, and ssDNA-binding protein, is the basis of chromosomal SOS untargeted mutagenesis.
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Affiliation(s)
- A Maor-Shoshani
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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37
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Daube SS, Tomer G, Livneh Z. Translesion replication by DNA polymerase delta depends on processivity accessory proteins and differs in specificity from DNA polymerase beta. Biochemistry 2000; 39:348-55. [PMID: 10630995 DOI: 10.1021/bi9917784] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mutations caused by DNA damage lead to the development of cancer. The critical step in the formation of these mutations is the replication of unrepaired lesions in DNA by DNA polymerases, a process termed translesion replication. Using a newly developed method for preparation of gapped plasmids, containing a site-specific synthetic abasic site, we analyzed translesion replication with purified mammalian DNA polymerases delta and beta. DNA polymerase delta was found to be unable to replicate through the abasic site. Addition of the sliding DNA clamp PCNA, the clamp loader RFC, and ATP caused a drastic 30-fold increase in translesion replication. Thus, similar to Escherichia coli DNA polymerase III, the processivity accessory proteins enable DNA polymerase delta to bypass blocking lesions. Under comparable conditions, DNA polymerase beta was unable to bypass the abasic site, unless its concentration was greatly increased. Analysis of translesion replication products revealed a marked difference in the specificity of bypass: whereas 90% of bypass events by DNA polymerase delta holoenzyme involved insertion of a dAMP residue opposite the abasic site, DNA polymerase beta tended to skip over the abasic site, producing mainly minus frameshifts (73%). The significance of these results for in vivo translesion replication is discussed.
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Affiliation(s)
- S S Daube
- Department of Biological Chemistry, Faculty of Biochemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
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38
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Abstract
Ultraviolet (UV) radiation has been an important environmental parameter during the evolution of life on Earth, both in its role as a mutagen and as a selective agent. This was probably especially true during the time from 3.8 to 2.5 billion years ago, when atmospheric ozone levels were less than 1% of present levels. Early Mars may not have had an "ozone shield" either, and it never developed a significant one. Even though Mars is farther away from the Sun than the Earth, a substantial surficial UV flux is present on Mars today. But organisms respond to dose rate, and on Mars, like on Earth, organisms would be exposed to diurnal variations in UV flux. Here we present data on the effect of diurnal patterns of UV flux on microbial ecosystems in nature, with an emphasis on photosynthesis and DNA synthesis effects. These results indicate that diurnal patterns of metabolism occur in nature with a dip in photosynthesis and DNA synthesis in the afternoon, in part regulated by UV flux. Thus, diurnal patterns must be studied in order to understand the effect of UV radiation in nature. The results of this work are significant to the success of human missions to Mars for several reasons. For example, human missions must include photosynthetic organisms for food production and likely oxygen production. An evolutionary approach suggests which organisms might be best suited for high UV fluxes. The diurnal aspect of these studies is critical. Terraforming is a potential goal of Mars exploration, and it will require studies of the effect of Martian UV fluxes, including their diurnal changes, on terrestrial organisms. Such studies may suggest that diurnal changes in UV only require mitigation at some times of day or year.
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Affiliation(s)
- L J Rothschild
- Ecosystem Science and Technology Branch, Mail Stop 239-20, NASA Ames Research Center, Moffett Field, CA, USA.
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39
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Reuven NB, Arad G, Maor-Shoshani A, Livneh Z. The mutagenesis protein UmuC is a DNA polymerase activated by UmuD', RecA, and SSB and is specialized for translesion replication. J Biol Chem 1999; 274:31763-6. [PMID: 10542196 DOI: 10.1074/jbc.274.45.31763] [Citation(s) in RCA: 275] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Replication of DNA lesions leads to the formation of mutations. In Escherichia coli this process is regulated by the SOS stress response, and requires the mutagenesis proteins UmuC and UmuD'. Analysis of translesion replication using a recently reconstituted in vitro system (Reuven, N. B., Tomer, G., and Livneh, Z. (1998) Mol. Cell 2, 191-199) revealed that lesion bypass occurred with a UmuC fusion protein, UmuD', RecA, and SSB in the absence of added DNA polymerase. Further analysis revealed that UmuC was a DNA polymerase (E. coli DNA polymerase V), with a weak polymerizing activity. Upon addition of UmuD', RecA, and SSB, the UmuC DNA polymerase was greatly activated, and replicated a synthetic abasic site with great efficiency (45% bypass in 6 min), 10-100-fold higher than E. coli DNA polymerases I, II, or III holoenzyme. Analysis of bypass products revealed insertion of primarily dAMP (69%), and to a lesser degree dGMP (31%) opposite the abasic site. The UmuC104 mutant protein was defective both in lesion bypass and in DNA synthesis. These results indicate that UmuC is a UmuD'-, RecA-, and SSB-activated DNA polymerase, which is specialized for lesion bypass. UmuC is a member of a new family of DNA polymerases which are specialized for lesion bypass, and include the yeast RAD30 and the human XP-V genes, encoding DNA polymerase eta.
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Affiliation(s)
- N B Reuven
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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40
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Cox MM. Recombinational DNA repair in bacteria and the RecA protein. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1999; 63:311-66. [PMID: 10506835 DOI: 10.1016/s0079-6603(08)60726-6] [Citation(s) in RCA: 168] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
In bacteria, the major function of homologous genetic recombination is recombinational DNA repair. This is not a process reserved only for rare double-strand breaks caused by ionizing radiation, nor is it limited to situations in which the SOS response has been induced. Recombinational DNA repair in bacteria is closely tied to the cellular replication systems, and it functions to repair damage at stalled replication forks, Studies with a variety of rec mutants, carried out under normal aerobic growth conditions, consistently suggest that at least 10-30% of all replication forks originating at the bacterial origin of replication are halted by DNA damage and must undergo recombinational DNA repair. The actual frequency may be much higher. Recombinational DNA repair is both the most complex and the least understood of bacterial DNA repair processes. When replication forks encounter a DNA lesion or strand break, repair is mediated by an adaptable set of pathways encompassing most of the enzymes involved in DNA metabolism. There are five separate enzymatic processes involved in these repair events: (1) The replication fork assembled at OriC stalls and/or collapses when encountering DNA damage. (2) Recombination enzymes provide a complementary strand for a lesion isolated in a single-strand gap, or reconstruct a branched DNA at the site of a double-strand break. (3) The phi X174-type primosome (or repair primosome) functions in the origin-independent reassembly of the replication fork. (4) The XerCD site-specific recombination system resolves the dimeric chromosomes that are the inevitable by-product of frequent recombination associated with recombinational DNA repair. (5) DNA excision repair and other repair systems eliminate lesions left behind in double-stranded DNA. The RecA protein plays a central role in the recombination phase of the process. Among its many activities, RecA protein is a motor protein, coupling the hydrolysis of ATP to the movement of DNA branches.
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Affiliation(s)
- M M Cox
- Department of Biochemistry, University of Wisconsin-Madison 53706, USA
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41
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Atienzar FA, Conradi M, Evenden AJ, Jha AN, Depledge MH. Qualitative assessment of genotoxicity using random amplified polymorphic DNA: Comparison of genomic template stability with key fitness parameters in Daphnia magna exposed to benzo[a]pyrene. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 1999; 18:2275-2282. [PMID: 29857629 DOI: 10.1002/etc.5620181023] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/1998] [Accepted: 02/01/1999] [Indexed: 06/08/2023]
Abstract
A method of DNA profiling using the random amplified polymorphic DNA (RAPD) was used to assess toxicant-induced DNA effects in laboratory populations of Daphnia magna exposed to varying concentrations of the genotoxic hydrocarbon benzo[a]pyrene. These effects, represented by changes in the RAPD profiles, were compared with a number of key ecological fitness parameters (age-specific survival, age-specific fecundity, net reproductive rate, and intrinsic rate of population increase). Not only was the RAPD profiling method shown to be a rapid and reproducible assay of toxicant-induced DNA effects, but the qualitative measure of genomic template stability compared favorably with the traditional indices of fitness. The RAPD profiles, however, exhibited higher sensitivity in detecting toxic effects. The significance of these findings for future ecotoxicological studies is discussed.
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Affiliation(s)
- Franck A Atienzar
- Plymouth Environmental Research Center (PERC) and Department of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, United Kingdom
| | - Mercedes Conradi
- Plymouth Environmental Research Center (PERC) and Department of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, United Kingdom
| | - Andrew J Evenden
- Plymouth Environmental Research Center (PERC) and Department of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, United Kingdom
| | - Awadhesh N Jha
- Plymouth Environmental Research Center (PERC) and Department of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, United Kingdom
| | - Michael H Depledge
- Plymouth Environmental Research Center (PERC) and Department of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, United Kingdom
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42
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Tomer G, Livneh Z. Analysis of unassisted translesion replication by the DNA polymerase III holoenzyme. Biochemistry 1999; 38:5948-58. [PMID: 10231549 DOI: 10.1021/bi982599+] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
DNA damage-induced mutations are formed when damaged nucleotides present in single-stranded DNA are replicated. We have developed a new method for the preparation of gapped plasmids containing site-specific damaged nucleotides, as model DNA substrates for translesion replication. Using these substrates, we show that the DNA polymerase III holoenzyme from Escherichia coli can bypass a synthetic abasic site analogue with high efficiency (30% bypass in 16 min), unassisted by other proteins. The theta and tau subunits of the polymerase were not essential for bypass. No bypass was observed when the enzyme was assayed on a synthetic 60-mer oligonucleotide carrying the same lesion, and bypass on a linear gapped plasmid was 3-4-fold slower than on a circular gapped plasmid. There was no difference in the bypass when standing-start and running-start replication were compared. A comparison of translesion replication by DNA polymerase I, DNA polymerase II, the DNA polymerase III core, and the DNA polymerase III holoenzyme clearly showed that the DNA polymerase III holoenzyme was by far the most effective in performing translesion replication. This was not only due to the high processivity of the pol III holoenzyme, because increasing the processivity of pol II by adding the gamma complex and beta subunit, did not increase bypass. These results support the model that SOS regulation was imposed on a fundamentally constitutive translesion replication reaction to achieve tight control of mutagenesis.
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Affiliation(s)
- G Tomer
- Department of Biological Chemistry, Faculty of Biochemistry, The Weizmann Institute of Science, Rehovot, Israel
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43
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Broschard TH, Koffel-Schwartz N, Fuchs RP. Sequence-dependent modulation of frameshift mutagenesis at NarI-derived mutation hot spots. J Mol Biol 1999; 288:191-9. [PMID: 10329136 DOI: 10.1006/jmbi.1999.2667] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The NarI sequence is known to be the strongest mutation hot spot for induced frameshift mutagenesis. Indeed, a single N-2-acetylaminofluorene (AAF) adduct induces -2 frameshift mutations (5'-GGCGAAFCC--> 5'-GGCC) more than 10(7)-fold over background mutagenesis in Escherichia coli. The mechanism of induction of the frameshift mutation involves a two nucleotide primer-template misalignment event during replication of the adduct-containing sequence. The slipped mutagenic intermediate (SMI) that is thus formed is strongly stabilised by the AAF residue. In order to understand the origin of the extreme susceptibility of this sequence to frameshift mutagenesis, we analysed AAF-induced mutagenesis at sequences 5'-NaGCGAAFCNb-3' containing the core dinucleotide GCGC repeat present in the NarI sequence flanked by variable nucleotides Na and Nb. The nature of nucleotide Nb was found to strongly modulate the frequency of induced -2 frameshift mutagenesis (up to 30 to 50-fold), while little if any effect could be attributed to nucleotide Na. The induction of -2 frameshifts, regardless of nucleotides Na and Nb, was found to be SOS-inducible but umuDC-independent as previously found for the authentic NarI sequence. The NarI sequence (GGCGCC) and sequence TGCGCA (Na=T, Nb=A) were found to be equally "hot" for -2 frameshift mutation induction compared to the sequence AGCGCT where induced mutagenesis was 30 to 50-fold lower.The analysis of replication events using constructions containing a strand marker across from the adduct site allowed us to demonstrate that the large difference in -2 frameshift mutagenesis is due to an intrinsic difference in the propensity of these sequences to slip during replication. How the nature of the nucleotide flanking the adduct on its 3'-side (Nb) differentially stabilises the SMI will be discussed in the light of recent structural data and theoretical models.
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Affiliation(s)
- T H Broschard
- Cancerogenese et Mutagenese Moleculaire et Structurale, CNRS, Blvd Sébastien Brant, Strasbourg, 67400, France
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44
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Butenandt J, Burgdorf LT, Carell T. „Base Flipping”: UV-Licht-geschädigte DNA-RNA-Duplexe sind schlechte Substrate für photoreaktivierende DNA-Reparaturenzyme. Angew Chem Int Ed Engl 1999. [DOI: 10.1002/(sici)1521-3757(19990301)111:5<718::aid-ange718>3.0.co;2-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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45
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Ohta T, Sutton MD, Guzzo A, Cole S, Ferentz AE, Walker GC. Mutations affecting the ability of the Escherichia coli UmuD' protein to participate in SOS mutagenesis. J Bacteriol 1999; 181:177-85. [PMID: 9864328 PMCID: PMC103547 DOI: 10.1128/jb.181.1.177-185.1999] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The products of the SOS-regulated umuDC operon are required for most UV and chemical mutagenesis in Escherichia coli, a process that results from a translesion synthesis mechanism. The UmuD protein is activated for its role in mutagenesis by a RecA-facilitated autodigestion that removes the N-terminal 24 amino acids. A previous genetic screen for nonmutable umuD mutants had resulted in the isolation of a set of missense mutants that produced UmuD proteins that were deficient in RecA-mediated cleavage (J. R. Battista, T. Ohta, T. Nohmi, W. Sun, and G. C. Walker, Proc. Natl. Acad. Sci. USA 87:7190-7194, 1990). To identify elements of the UmuD' protein necessary for its role in translesion synthesis, we began with umuD', a modified form of the umuD gene that directly encodes the UmuD' protein, and obtained missense umuD' mutants deficient in UV and methyl methanesulfonate mutagenesis. The D39G, L40R, and T51I mutations affect residues located at the UmuD'2 homodimer interface and interfere with homodimer formation in vivo. The D75A mutation affects a highly conserved residue located at one end of the central strand in a three-stranded beta-sheet and appears to interfere with UmuD'2 homodimer formation indirectly by affecting the structure of the UmuD' monomer. When expressed from a multicopy plasmid, the L40R umuD' mutant gene exhibited a dominant negative effect on a chromosomal umuD+ gene with respect to UV mutagenesis, suggesting that the mutation has an effect on UmuD' function that goes beyond its impairment of homodimer formation. The G129D mutation affects a highly conserved residue that lies at the end of the long C-terminal beta-strand and results in a mutant UmuD' protein that exhibits a strongly dominant negative effect on UV mutagenesis in a umuD+ strain. The A30V and E35K mutations alter residues in the N-terminal arms of the UmuD'2 homodimer, which are mobile in solution.
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Affiliation(s)
- T Ohta
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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46
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Abstract
Nucleotide excision repair is both a 'wide spectrum' DNA repair pathway and the sole system for repairing bulky damages such as UV lesions or benzo[a]pyrene adducts. The mechanisms of nucleotide excision repair are known in considerable detail in Escherichia coli. Similarly, in the past 5 years important advances have been made towards understanding the biochemical mechanisms of excision repair in humans. The overall strategy of the repair is the same in the two species: damage recognition through a multistep mechanism involving a molecular matchmaker and an ATP-dependent unwinding of the damaged duplex; dual incisions at both sides of the lesion by two different nucleases, the 3' incision being followed by the 5'; removal of the damaged oligomer; resynthesis of the repair patch, whose length matches the gap size. Despite these similarities, the two systems are biochemically different and do not even share structural homology. E. coli excinuclease employs three proteins in contrast to 16/17 polypeptides in man; the excised fragment is longer in man: the procaryotic excinuclease is not able by itself to remove the excised oligomer whereas the human enzyme does. Thus, the excinuclease mode of action is well conserved throughout evolution, but not the biochemical tools: this represents a case of evolutionary convergence.
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Affiliation(s)
- C Petit
- University of North Carolina at Chapel Hill, School of Medicine, Department of Biochemistry and Biophysics, 27599-7260, USA
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47
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Abstract
Environmental and physiological stress conditions can transiently alter the fidelity of DNA replication. The DNA damage-mediated SOS response in Escherichia coli is the best-known example of such an 'inducible mutagenesis' or 'transient mutator' pathway. Emerging evidence suggests the existence of a number of other stress-inducible pathways that also affect the fidelity of replication. Among the more provocative recent findings are UVM, an SOS-independent damage-inducible mutagenic pathway, and a new recA-dependent but umuD/C-independent pathway that appears to be provoked by translational stress. These findings alter our view of inducible mutagenesis, and anticipate the existence of previously unrecognized links between protein synthesis and DNA replication.
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Affiliation(s)
- M Z Humayun
- Department of Microbiology and Molecular Genetics, UMDNJ - New Jersey Medical School, Newark 07103-2714, USA.
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48
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Tomer G, Reuven NB, Livneh Z. The beta subunit sliding DNA clamp is responsible for unassisted mutagenic translesion replication by DNA polymerase III holoenzyme. Proc Natl Acad Sci U S A 1998; 95:14106-11. [PMID: 9826661 PMCID: PMC24334 DOI: 10.1073/pnas.95.24.14106] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The replication of damaged nucleotides that have escaped DNA repair leads to the formation of mutations caused by misincorporation opposite the lesion. In Escherichia coli, this process is under tight regulation of the SOS stress response and is carried out by DNA polymerase III in a process that involves also the RecA, UmuD' and UmuC proteins. We have shown that DNA polymerase III holoenzyme is able to replicate, unassisted, through a synthetic abasic site in a gapped duplex plasmid. Here, we show that DNA polymerase III*, a subassembly of DNA polymerase III holoenzyme lacking the beta subunit, is blocked very effectively by the synthetic abasic site in the same DNA substrate. Addition of the beta subunit caused a dramatic increase of at least 28-fold in the ability of the polymerase to perform translesion replication, reaching 52% bypass in 5 min. When the ssDNA region in the gapped plasmid was extended from 22 nucleotides to 350 nucleotides, translesion replication still depended on the beta subunit, but it was reduced by 80%. DNA sequence analysis of translesion replication products revealed mostly -1 frameshifts. This mutation type is changed to base substitution by the addition of UmuD', UmuC, and RecA, as demonstrated in a reconstituted SOS translesion replication reaction. These results indicate that the beta subunit sliding DNA clamp is the major determinant in the ability of DNA polymerase III holoenzyme to perform unassisted translesion replication and that this unassisted bypass produces primarily frameshifts.
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Affiliation(s)
- G Tomer
- Department of Biological Chemistry, Faculty of Biochemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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49
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Fuchs RP, Napolitano RL. Inactivation of DNA proofreading obviates the need for SOS induction in frameshift mutagenesis. Proc Natl Acad Sci U S A 1998; 95:13114-9. [PMID: 9789050 PMCID: PMC23728 DOI: 10.1073/pnas.95.22.13114] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Translesion synthesis at replication-blocking lesions requires the induction of proteins that are controlled by the SOS system in Escherichia coli. Of the proteins identified so far, UmuD', UmuC, and RecA* were shown to facilitate replication across UV-light-induced lesions, yielding both error-free and mutagenic translesion-synthesis products. Similar to UV lesions, N-2-acetylaminofluorene (AAF), a chemical carcinogen that forms covalent adducts at the C8 position of guanine residues, is a strong replication-blocking lesion. Frameshift mutations are induced efficiently by AAF adducts when located within short repetitive sequences in a two-step mechanism; AAF adducts incorporate a cytosine across from the lesion and then form a primer-template misaligned intermediate that, upon elongation, yields frameshift mutations. Recently, we have shown that although elongation from the nonslipped intermediate depends on functional umuDC+ gene products, elongation from the slipped intermediate is umuDC+-independent but requires another, as yet biochemically uncharacterized, SOS function. We now show that in DNA Polymerase III-proofreading mutant strains (dnaQ49 and mutD5 strains), elongation from the slipped intermediate is highly efficient in the absence of SOS induction-in contrast to elongation from the nonslipped intermediate, which still requires UmuDC functions.
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Affiliation(s)
- R P Fuchs
- Cancérogenèse et Mutagenèse Moléculaire et Structurale, Unité Propre de Recherche 9003 du Centre National de la Recherche Scientifique, Strasbourg, France.
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50
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Sedliakova M. A non-excision uvr-dependent DNA repair pathway of Escherichia coli (involvement of stress proteins). JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 1998; 45:75-81. [PMID: 9868797 DOI: 10.1016/s1011-1344(98)00159-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In UV-irradiated excision-proficient (uvr+) Escherichia coli, pre-induced by simultaneous pre-starvation for thymine (T) and amino acids (AAs), and/or a low UV pre-dose applied after prestarvation for AAs, pyrimidine dimer excision (PDE) is reduced without an adequate increase of UV sensitivity and UV mutagenesis. The unexcised lesions are tolerated by a putative repair pathway that is uvr dependent but does not involve excision. The process consists of PDE inhibition, which requires outer membrane protease OmpT, and subsequent pyrimidine dimer (PD) toleration, which may be mediated by interaction with a sister duplex using a number of SOS and stress-inducible proteins.
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Affiliation(s)
- M Sedliakova
- Cancer Research Institute, Slovak Academy of Sciences, Bratislava, Slovak Republic.
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