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Grasso L, Fonzino A, Manzari C, Leonardi T, Picardi E, Gissi C, Lazzaro F, Pesole G, Muzi-Falconi M. Detection of ribonucleotides embedded in DNA by Nanopore sequencing. Commun Biol 2024; 7:491. [PMID: 38654143 DOI: 10.1038/s42003-024-06077-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 03/20/2024] [Indexed: 04/25/2024] Open
Abstract
Ribonucleotides represent the most common non-canonical nucleotides found in eukaryotic genomes. The sources of chromosome-embedded ribonucleotides and the mechanisms by which unrepaired rNMPs trigger genome instability and human pathologies are not fully understood. The available sequencing technologies only allow to indirectly deduce the genomic location of rNMPs. Oxford Nanopore Technologies (ONT) may overcome such limitation, revealing the sites of rNMPs incorporation in genomic DNA directly from raw sequencing signals. We synthesized two types of DNA molecules containing rNMPs at known or random positions and we developed data analysis pipelines for DNA-embedded ribonucleotides detection by ONT. We report that ONT can identify all four ribonucleotides incorporated in DNA by capturing rNMPs-specific alterations in nucleotide alignment features, current intensity, and dwell time. We propose that ONT may be successfully employed to directly map rNMPs in genomic DNA and we suggest a strategy to build an ad hoc basecaller to analyse native genomes.
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Affiliation(s)
- Lavinia Grasso
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133, Milano, Italy
| | - Adriano Fonzino
- Dipartimento di Bioscienze, Biotecnologie e Ambiente, Università di Bari A. Moro, Via Orabona 4, 70126, Bari, Italy
| | - Caterina Manzari
- Dipartimento di Bioscienze, Biotecnologie e Ambiente, Università di Bari A. Moro, Via Orabona 4, 70126, Bari, Italy
| | - Tommaso Leonardi
- Center for Genomic Science of IIT@SEMM, Fondazione Istituto Italiano di Tecnologia, Via Adamello 16, 20139, Milano, Italy
| | - Ernesto Picardi
- Dipartimento di Bioscienze, Biotecnologie e Ambiente, Università di Bari A. Moro, Via Orabona 4, 70126, Bari, Italy
- Istituto di Biomembrane, Bioenergetica e Biotecnologie Molecolari, Consiglio Nazionale delle Ricerche, Via Amendola 122/O, 70126, Bari, Italy
| | - Carmela Gissi
- Dipartimento di Bioscienze, Biotecnologie e Ambiente, Università di Bari A. Moro, Via Orabona 4, 70126, Bari, Italy
- Istituto di Biomembrane, Bioenergetica e Biotecnologie Molecolari, Consiglio Nazionale delle Ricerche, Via Amendola 122/O, 70126, Bari, Italy
| | - Federico Lazzaro
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133, Milano, Italy.
| | - Graziano Pesole
- Dipartimento di Bioscienze, Biotecnologie e Ambiente, Università di Bari A. Moro, Via Orabona 4, 70126, Bari, Italy.
- Istituto di Biomembrane, Bioenergetica e Biotecnologie Molecolari, Consiglio Nazionale delle Ricerche, Via Amendola 122/O, 70126, Bari, Italy.
| | - Marco Muzi-Falconi
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133, Milano, Italy.
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2
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Size- and Stereochemistry-Dependent Transcriptional Bypass of DNA Alkyl Phosphotriester Adducts in Mammalian Cells. DNA 2022; 2:221-230. [PMID: 36911626 PMCID: PMC9997456 DOI: 10.3390/dna2040016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Environmental, endogenous and therapeutic alkylating agents can react with internucleotide phosphate groups in DNA to yield alkyl phosphotriester (PTE) adducts. Alkyl-PTEs are induced at relatively high frequencies and are persistent in mammalian tissues; however, their biological consequences in mammalian cells have not been examined. Herein, we assessed how alkyl-PTEs with different alkyl group sizes and stereochemical configurations (S P and R P diastereomers of Me and nPr) affect the efficiency and fidelity of transcription in mammalian cells. We found that, while the R P diastereomer of Me- and nPr-PTEs constituted moderate and strong blockages to transcription, respectively, the S P diastereomer of the two lesions did not appreciably perturb transcription efficiency. In addition, none of the four alkyl-PTEs induced mutant transcripts. Furthermore, polymerase η assumed an important role in promoting transcription across the S P-Me-PTE, but not any of other three lesions. Loss of other translesion synthesis (TLS) polymerases tested, including Pol κ, Pol ι, Pol ξ and REV1, did not alter the transcription bypass efficiency or mutation frequency for any of the alkyl-PTE lesions. Together, our study provided important new knowledge about the impact of alkyl-PTE lesions on transcription and expanded the substrate pool of Pol η in transcriptional bypass.
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3
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Weaver TM, Click TH, Khoang TH, Todd Washington M, Agarwal PK, Freudenthal BD. Mechanism of nucleotide discrimination by the translesion synthesis polymerase Rev1. Nat Commun 2022; 13:2876. [PMID: 35610266 PMCID: PMC9130138 DOI: 10.1038/s41467-022-30577-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 05/06/2022] [Indexed: 11/09/2022] Open
Abstract
Rev1 is a translesion DNA synthesis (TLS) polymerase involved in the bypass of adducted-guanine bases and abasic sites during DNA replication. During damage bypass, Rev1 utilizes a protein-template mechanism of DNA synthesis, where the templating DNA base is evicted from the Rev1 active site and replaced by an arginine side chain that preferentially binds incoming dCTP. Here, we utilize X-ray crystallography and molecular dynamics simulations to obtain structural insight into the dCTP specificity of Rev1. We show the Rev1 R324 protein-template forms sub-optimal hydrogen bonds with incoming dTTP, dGTP, and dATP that prevents Rev1 from adopting a catalytically competent conformation. Additionally, we show the Rev1 R324 protein-template forms optimal hydrogen bonds with incoming rCTP. However, the incoming rCTP adopts an altered sugar pucker, which prevents the formation of a catalytically competent Rev1 active site. This work provides novel insight into the mechanisms for nucleotide discrimination by the TLS polymerase Rev1.
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Affiliation(s)
- Tyler M Weaver
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, Kansas, 66160, USA.,Department of Cancer Biology, University of Kansas Medical Center, Kansas City, Kansas, 66160, USA
| | - Timothy H Click
- Department of Physiological Sciences and High-Performance Computing Center, Oklahoma State University, Stillwater, Oklahoma, 74048, USA
| | - Thu H Khoang
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, Kansas, 66160, USA.,Department of Cancer Biology, University of Kansas Medical Center, Kansas City, Kansas, 66160, USA
| | - M Todd Washington
- Department of Biochemistry and Molecular Biology, University of Iowa, Iowa City, IA, 52242, USA
| | - Pratul K Agarwal
- Department of Physiological Sciences and High-Performance Computing Center, Oklahoma State University, Stillwater, Oklahoma, 74048, USA.
| | - Bret D Freudenthal
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, Kansas, 66160, USA. .,Department of Cancer Biology, University of Kansas Medical Center, Kansas City, Kansas, 66160, USA.
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4
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Balint E, Unk I. Manganese Is a Strong Specific Activator of the RNA Synthetic Activity of Human Polη. Int J Mol Sci 2021; 23:ijms23010230. [PMID: 35008656 PMCID: PMC8745064 DOI: 10.3390/ijms23010230] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 12/21/2021] [Accepted: 12/23/2021] [Indexed: 12/02/2022] Open
Abstract
DNA polymerase η (Polη) is a translesion synthesis polymerase that can bypass different DNA lesions with varying efficiency and fidelity. Its most well-known function is the error-free bypass of ultraviolet light-induced cyclobutane pyrimidine dimers. The lack of this unique ability in humans leads to the development of a cancer-predisposing disease, the variant form of xeroderma pigmentosum. Human Polη can insert rNTPs during DNA synthesis, though with much lower efficiency than dNTPs, and it can even extend an RNA chain with ribonucleotides. We have previously shown that Mn2+ is a specific activator of the RNA synthetic activity of yeast Polη that increases the efficiency of the reaction by several thousand-fold over Mg2+. In this study, our goal was to investigate the metal cofactor dependence of RNA synthesis by human Polη. We found that out of the investigated metal cations, only Mn2+ supported robust RNA synthesis. Steady state kinetic analysis showed that Mn2+ activated the reaction a thousand-fold compared to Mg2+, even during DNA damage bypass opposite 8-oxoG and TT dimer. Our results revealed a two order of magnitude higher affinity of human Polη towards ribonucleotides in the presence of Mn2+ compared to Mg2+. It is noteworthy that activation occurred without lowering the base selectivity of the enzyme on undamaged templates, whereas the fidelity decreased across a TT dimer. In summary, our data strongly suggest that, like with its yeast homolog, Mn2+ is the proper metal cofactor of hPolη during RNA chain extension, and selective metal cofactor utilization contributes to switching between its DNA and RNA synthetic activities.
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5
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Lassègue B, Kumar S, Mandavilli R, Wang K, Tsai M, Kang DW, Demos C, Hernandes MS, San Martín A, Taylor WR, Jo H, Griendling KK. Characterization of Poldip2 knockout mice: Avoiding incorrect gene targeting. PLoS One 2021; 16:e0247261. [PMID: 34928942 PMCID: PMC8687530 DOI: 10.1371/journal.pone.0247261] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 11/17/2021] [Indexed: 01/11/2023] Open
Abstract
POLDIP2 is a multifunctional protein whose roles are only partially understood. Our laboratory previously reported physiological studies performed using a mouse gene trap model, which suffered from three limitations: perinatal lethality in homozygotes, constitutive Poldip2 inactivation and inadvertent downregulation of the adjacent Tmem199 gene. To overcome these limitations, we developed a new conditional floxed Poldip2 model. The first part of the present study shows that our initial floxed mice were affected by an unexpected mutation, which was not readily detected by Southern blotting and traditional PCR. It consisted of a 305 kb duplication around Poldip2 with retention of the wild type allele and could be traced back to the original targeted ES cell clone. We offer simple suggestions to rapidly detect similar accidents, which may affect genome editing using both traditional and CRISPR-based methods. In the second part of the present study, correctly targeted floxed Poldip2 mice were generated and used to produce a new constitutive knockout line by crossing with a Cre deleter. In contrast to the gene trap model, many homozygous knockout mice were viable, in spite of having no POLDIP2 expression. To further characterize the effects of Poldip2 ablation in the vasculature, RNA-seq and RT-qPCR experiments were performed in constitutive knockout arteries. Results show that POLDIP2 inactivation affects multiple cellular processes and provide new opportunities for future in-depth study of its functions.
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Affiliation(s)
- Bernard Lassègue
- Division of Cardiology, Department of Medicine, Emory University, Atlanta, GA, United States of America
| | - Sandeep Kumar
- Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, United States of America
| | - Rohan Mandavilli
- Division of Cardiology, Department of Medicine, Emory University, Atlanta, GA, United States of America
| | - Keke Wang
- Division of Cardiology, Department of Medicine, Emory University, Atlanta, GA, United States of America
| | - Michelle Tsai
- Division of Cardiology, Department of Medicine, Emory University, Atlanta, GA, United States of America
| | - Dong-Won Kang
- Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, United States of America
| | - Catherine Demos
- Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, United States of America
| | - Marina S. Hernandes
- Division of Cardiology, Department of Medicine, Emory University, Atlanta, GA, United States of America
| | - Alejandra San Martín
- Division of Cardiology, Department of Medicine, Emory University, Atlanta, GA, United States of America
| | - W. Robert Taylor
- Division of Cardiology, Department of Medicine, Emory University, Atlanta, GA, United States of America
- Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, United States of America
- Division of Cardiology, Atlanta VA Medical Center, Decatur, GA, United States of America
| | - Hanjoong Jo
- Division of Cardiology, Department of Medicine, Emory University, Atlanta, GA, United States of America
- Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, United States of America
| | - Kathy K. Griendling
- Division of Cardiology, Department of Medicine, Emory University, Atlanta, GA, United States of America
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6
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Tan Y, Guo S, Wu J, Du H, Li L, You C, Wang Y. DNA Polymerase η Promotes the Transcriptional Bypass of N2-Alkyl-2'-deoxyguanosine Adducts in Human Cells. J Am Chem Soc 2021; 143:16197-16205. [PMID: 34555898 DOI: 10.1021/jacs.1c07374] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
To cope with unrepaired DNA lesions, cells are equipped with DNA damage tolerance mechanisms, including translesion synthesis (TLS). While TLS polymerases are well documented in facilitating replication across damaged DNA templates, it remains unknown whether TLS polymerases participate in transcriptional bypass of DNA lesions in cells. Herein, we employed the competitive transcription and adduct bypass assay to examine the efficiencies and fidelities of transcription across N2-alkyl-2'-deoxyguanosine (N2-alkyl-dG, alkyl = methyl, ethyl, n-propyl, or n-butyl) lesions in HEK293T cells. We found that N2-alkyl-dG lesions strongly blocked transcription and elicited CC → AA tandem mutations in nascent transcripts, where adenosines were misincorporated opposite the lesions and their adjacent 5' nucleoside. Additionally, genetic ablation of Pol η, but not Pol κ, Pol ι, or Pol ζ, conferred marked diminutions in the transcriptional bypass efficiencies of the N2-alkyl-dG lesions, which is exacerbated by codepletion of Rev1 in Pol η-deficient background. We also observed that the repair of N2-nBu-dG was not pronouncedly affected by genetic depletion of Pol η or Rev1. Hence, our results provided insights into transcriptional perturbations induced by N2-alkyl-dG lesions and expanded the biological functions of TLS DNA polymerases.
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Affiliation(s)
- Ying Tan
- Environmental Toxicology Graduate Program, University of California, Riverside, California 92521-0403, United States
| | - Su Guo
- Environmental Toxicology Graduate Program, University of California, Riverside, California 92521-0403, United States
| | - Jun Wu
- Department of Chemistry, University of California, Riverside, California 92521-0403, United States
| | - Hua Du
- Department of Chemistry, University of California, Riverside, California 92521-0403, United States
| | - Lin Li
- Department of Chemistry, University of California, Riverside, California 92521-0403, United States
| | - Changjun You
- Department of Chemistry, University of California, Riverside, California 92521-0403, United States
| | - Yinsheng Wang
- Environmental Toxicology Graduate Program, University of California, Riverside, California 92521-0403, United States.,Department of Chemistry, University of California, Riverside, California 92521-0403, United States
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7
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High Flexibility of RNaseH2 Catalytic Activity with Respect to Non-Canonical DNA Structures. Int J Mol Sci 2021; 22:ijms22105201. [PMID: 34068992 PMCID: PMC8155979 DOI: 10.3390/ijms22105201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2021] [Revised: 05/11/2021] [Accepted: 05/12/2021] [Indexed: 11/17/2022] Open
Abstract
Ribonucleotides misincorporated in the human genome are the most abundant DNA lesions. The 2'-hydroxyl group makes them prone to spontaneous hydrolysis, potentially resulting in strand breaks. Moreover, their presence may decrease the rate of DNA replication causing replicative fork stalling and collapse. Ribonucleotide removal is initiated by Ribonuclease H2 (RNase H2), the key player in Ribonucleotide Excision Repair (RER). Its absence leads to embryonic lethality in mice, while mutations decreasing its activity cause Aicardi-Goutières syndrome. DNA geometry can be altered by DNA lesions or by peculiar sequences forming secondary structures, like G-quadruplex (G4) and trinucleotide repeats (TNR) hairpins, which significantly differ from canonical B-form. Ribonucleotides pairing to lesioned nucleotides, or incorporated within non-B DNA structures could avoid RNase H2 recognition, potentially contributing to genome instability. In this work, we investigate the ability of RNase H2 to process misincorporated ribonucleotides in a panel of DNA substrates showing different geometrical features. RNase H2 proved to be a flexible enzyme, recognizing as a substrate the majority of the constructs we generated. However, some geometrical features and non-canonical DNA structures severely impaired its activity, suggesting a relevant role of misincorporated ribonucleotides in the physiological instability of specific DNA sequences.
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8
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Ashour ME, Mosammaparast N. Mechanisms of damage tolerance and repair during DNA replication. Nucleic Acids Res 2021; 49:3033-3047. [PMID: 33693881 PMCID: PMC8034635 DOI: 10.1093/nar/gkab101] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 01/28/2021] [Accepted: 03/02/2021] [Indexed: 01/05/2023] Open
Abstract
Accurate duplication of chromosomal DNA is essential for the transmission of genetic information. The DNA replication fork encounters template lesions, physical barriers, transcriptional machinery, and topological barriers that challenge the faithful completion of the replication process. The flexibility of replisomes coupled with tolerance and repair mechanisms counteract these replication fork obstacles. The cell possesses several universal mechanisms that may be activated in response to various replication fork impediments, but it has also evolved ways to counter specific obstacles. In this review, we will discuss these general and specific strategies to counteract different forms of replication associated damage to maintain genomic stability.
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Affiliation(s)
- Mohamed Elsaid Ashour
- Department of Pathology & Immunology, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA
| | - Nima Mosammaparast
- Department of Pathology & Immunology, Washington University in St. Louis School of Medicine, St. Louis, MO 63110, USA
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9
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Riva V, Garbelli A, Casiraghi F, Arena F, Trivisani CI, Gagliardi A, Bini L, Schroeder M, Maffia A, Sabbioneda S, Maga G. Novel alternative ribonucleotide excision repair pathways in human cells by DDX3X and specialized DNA polymerases. Nucleic Acids Res 2021; 48:11551-11565. [PMID: 33137198 PMCID: PMC7672437 DOI: 10.1093/nar/gkaa948] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 10/02/2020] [Accepted: 10/08/2020] [Indexed: 01/02/2023] Open
Abstract
Removal of ribonucleotides (rNMPs) incorporated into the genome by the ribonucleotide excision repair (RER) is essential to avoid genetic instability. In eukaryotes, the RNaseH2 is the only known enzyme able to incise 5' of the rNMP, starting the RER process, which is subsequently carried out by replicative DNA polymerases (Pols) δ or ϵ, together with Flap endonuclease 1 (Fen-1) and DNA ligase 1. Here, we show that the DEAD-box RNA helicase DDX3X has RNaseH2-like activity and can support fully reconstituted in vitro RER reactions, not only with Pol δ but also with the repair Pols β and λ. Silencing of DDX3X causes accumulation of rNMPs in the cellular genome. These results support the existence of alternative RER pathways conferring high flexibility to human cells in responding to the threat posed by rNMPs incorporation.
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Affiliation(s)
- Valentina Riva
- Institute of Molecular Genetics IGM-CNR 'Luigi Luca Cavalli-Sforza', via Abbiategrasso 207, I-27100 Pavia, Italy
| | - Anna Garbelli
- Institute of Molecular Genetics IGM-CNR 'Luigi Luca Cavalli-Sforza', via Abbiategrasso 207, I-27100 Pavia, Italy
| | - Federica Casiraghi
- Institute of Molecular Genetics IGM-CNR 'Luigi Luca Cavalli-Sforza', via Abbiategrasso 207, I-27100 Pavia, Italy
| | - Francesca Arena
- Institute of Molecular Genetics IGM-CNR 'Luigi Luca Cavalli-Sforza', via Abbiategrasso 207, I-27100 Pavia, Italy
| | - Claudia Immacolata Trivisani
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Via A. De Gasperi 2, I-53100 Siena, Italy
| | - Assunta Gagliardi
- Department of Life Sciences, Via A. Moro 2, University of Siena, I-53100 Siena, Italy
| | - Luca Bini
- Department of Life Sciences, Via A. Moro 2, University of Siena, I-53100 Siena, Italy
| | - Martina Schroeder
- Kathleen Lonsdale Institute for Human Health Research, Biology Department, Maynooth University, Maynooth, Co. Kildare, Ireland
| | - Antonio Maffia
- Institute of Molecular Genetics IGM-CNR 'Luigi Luca Cavalli-Sforza', via Abbiategrasso 207, I-27100 Pavia, Italy
| | - Simone Sabbioneda
- Institute of Molecular Genetics IGM-CNR 'Luigi Luca Cavalli-Sforza', via Abbiategrasso 207, I-27100 Pavia, Italy
| | - Giovanni Maga
- Institute of Molecular Genetics IGM-CNR 'Luigi Luca Cavalli-Sforza', via Abbiategrasso 207, I-27100 Pavia, Italy
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10
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Selective Metal Ion Utilization Contributes to the Transformation of the Activity of Yeast Polymerase η from DNA Polymerization toward RNA Polymerization. Int J Mol Sci 2020; 21:ijms21218248. [PMID: 33158019 PMCID: PMC7672554 DOI: 10.3390/ijms21218248] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 10/30/2020] [Accepted: 11/02/2020] [Indexed: 12/16/2022] Open
Abstract
Polymerase eta (Polη) is a translesion synthesis DNA polymerase directly linked to cancer development. It can bypass several DNA lesions thereby rescuing DNA damage-stalled replication complexes. We previously presented evidence implicating Saccharomyces cerevisiae Polη in transcription elongation, and identified its specific RNA extension and translesion RNA synthetic activities. However, RNA synthesis by Polη proved rather inefficient under conditions optimal for DNA synthesis. Searching for factors that could enhance its RNA synthetic activity, we have identified the divalent cation of manganese. Here, we show that manganese triggers drastic changes in the activity of Polη. Kinetics experiments indicate that manganese increases the efficiency of ribonucleoside incorporation into RNA by ~400–2000-fold opposite undamaged DNA, and ~3000 and ~6000-fold opposite TT dimer and 8oxoG, respectively. Importantly, preference for the correct base is maintained with manganese during RNA synthesis. In contrast, activity is strongly impaired, and base discrimination is almost lost during DNA synthesis by Polη with manganese. Moreover, Polη shows strong preference for manganese during RNA synthesis even at a 25-fold excess magnesium concentration. Based on this, we suggest that a new regulatory mechanism, selective metal cofactor utilization, modulates the specificity of Polη helping it to perform distinct activities needed for its separate functions during replication and transcription.
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11
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Johnson MK, Kottur J, Nair DT. A polar filter in DNA polymerases prevents ribonucleotide incorporation. Nucleic Acids Res 2020; 47:10693-10705. [PMID: 31544946 PMCID: PMC6846668 DOI: 10.1093/nar/gkz792] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 09/02/2019] [Accepted: 09/09/2019] [Indexed: 12/17/2022] Open
Abstract
The presence of ribonucleotides in DNA can lead to genomic instability and cellular lethality. To prevent adventitious rNTP incorporation, the majority of the DNA polymerases (dPols) possess a steric filter. The dPol named MsDpo4 (Mycobacterium smegmatis) naturally lacks this steric filter and hence is capable of rNTP addition. The introduction of the steric filter in MsDpo4 did not result in complete abrogation of the ability of this enzyme to incorporate ribonucleotides. In comparison, DNA polymerase IV (PolIV) from Escherichia coli exhibited stringent selection for deoxyribonucleotides. A comparison of MsDpo4 and PolIV led to the discovery of an additional polar filter responsible for sugar selectivity. Thr43 represents the filter in PolIV and this residue forms interactions with the incoming nucleotide to draw it closer to the enzyme surface. As a result, the 2’-OH in rNTPs will clash with the enzyme surface, and therefore ribonucleotides cannot be accommodated in the active site in a conformation compatible with productive catalysis. The substitution of the equivalent residue in MsDpo4–Cys47, with Thr led to a drastic reduction in the ability of the mycobacterial enzyme to incorporate rNTPs. Overall, our studies evince that the polar filter serves to prevent ribonucleotide incorporation by dPols.
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Affiliation(s)
- Mary K Johnson
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121001, India.,National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bangalore 560065, India
| | - Jithesh Kottur
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121001, India
| | - Deepak T Nair
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121001, India
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12
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Ghodke PP, Guengerich FP. Impact of 1, N 6-ethenoadenosine, a damaged ribonucleotide in DNA, on translesion synthesis and repair. J Biol Chem 2020; 295:6092-6107. [PMID: 32213600 DOI: 10.1074/jbc.ra120.012829] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 03/23/2020] [Indexed: 01/02/2023] Open
Abstract
Incorporation of ribonucleotides into DNA can severely diminish genome integrity. However, how ribonucleotides instigate DNA damage is poorly understood. In DNA, they can promote replication stress and genomic instability and have been implicated in several diseases. We report here the impact of the ribonucleotide rATP and of its naturally occurring damaged analog 1,N 6-ethenoadenosine (1,N 6-ϵrA) on translesion synthesis (TLS), mediated by human DNA polymerase η (hpol η), and on RNase H2-mediated incision. Mass spectral analysis revealed that 1,N 6-ϵrA in DNA generates extensive frameshifts during TLS, which can lead to genomic instability. Moreover, steady-state kinetic analysis of the TLS process indicated that deoxypurines (i.e. dATP and dGTP) are inserted predominantly opposite 1,N 6-ϵrA. We also show that hpol η acts as a reverse transcriptase in the presence of damaged ribonucleotide 1,N 6-ϵrA but has poor RNA primer extension activities. Steady-state kinetic analysis of reverse transcription and RNA primer extension showed that hpol η favors the addition of dATP and dGTP opposite 1,N 6-ϵrA. We also found that RNase H2 recognizes 1,N 6-ϵrA but has limited incision activity across from this lesion, which can lead to the persistence of this detrimental DNA adduct. We conclude that the damaged and unrepaired ribonucleotide 1,N 6-ϵrA in DNA exhibits mutagenic potential and can also alter the reading frame in an mRNA transcript because 1,N 6-ϵrA is incompletely incised by RNase H2.
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Affiliation(s)
- Pratibha P Ghodke
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37323-0146
| | - F Peter Guengerich
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37323-0146.
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13
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Nava GM, Grasso L, Sertic S, Pellicioli A, Muzi Falconi M, Lazzaro F. One, No One, and One Hundred Thousand: The Many Forms of Ribonucleotides in DNA. Int J Mol Sci 2020; 21:E1706. [PMID: 32131532 PMCID: PMC7084774 DOI: 10.3390/ijms21051706] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 02/26/2020] [Accepted: 02/28/2020] [Indexed: 12/14/2022] Open
Abstract
In the last decade, it has become evident that RNA is frequently found in DNA. It is now well established that single embedded ribonucleoside monophosphates (rNMPs) are primarily introduced by DNA polymerases and that longer stretches of RNA can anneal to DNA, generating RNA:DNA hybrids. Among them, the most studied are R-loops, peculiar three-stranded nucleic acid structures formed upon the re-hybridization of a transcript to its template DNA. In addition, polyribonucleotide chains are synthesized to allow DNA replication priming, double-strand breaks repair, and may as well result from the direct incorporation of consecutive rNMPs by DNA polymerases. The bright side of RNA into DNA is that it contributes to regulating different physiological functions. The dark side, however, is that persistent RNA compromises genome integrity and genome stability. For these reasons, the characterization of all these structures has been under growing investigation. In this review, we discussed the origin of single and multiple ribonucleotides in the genome and in the DNA of organelles, focusing on situations where the aberrant processing of RNA:DNA hybrids may result in multiple rNMPs embedded in DNA. We concluded by providing an overview of the currently available strategies to study the presence of single and multiple ribonucleotides in DNA in vivo.
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Affiliation(s)
| | | | | | | | - Marco Muzi Falconi
- Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, 20133 Milano, Italy; (G.M.N.); (L.G.); (S.S.); (A.P.)
| | - Federico Lazzaro
- Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, 20133 Milano, Italy; (G.M.N.); (L.G.); (S.S.); (A.P.)
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14
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Gupta A, Lad SB, Ghodke PP, Pradeepkumar PI, Kondabagil K. Mimivirus encodes a multifunctional primase with DNA/RNA polymerase, terminal transferase and translesion synthesis activities. Nucleic Acids Res 2019; 47:6932-6945. [PMID: 31001622 PMCID: PMC6648351 DOI: 10.1093/nar/gkz236] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 03/04/2019] [Accepted: 04/18/2019] [Indexed: 11/24/2022] Open
Abstract
Acanthamoeba polyphaga mimivirus is an amoeba-infecting giant virus with over 1000 genes including several involved in DNA replication and repair. Here, we report the biochemical characterization of gene product 577 (gp577), a hypothetical protein (product of L537 gene) encoded by mimivirus. Sequence analysis and phylogeny suggested gp577 to be a primase-polymerase (PrimPol)-the first PrimPol to be identified in a nucleocytoplasmic large DNA virus (NCLDV). Recombinant gp577 protein purified as a homodimer and exhibited de novo RNA as well as DNA synthesis on circular and linear single-stranded DNA templates. Further, gp577 extends a DNA/RNA primer annealed to a DNA or RNA template using deoxyribonucleoties (dNTPs) or ribonucleotides (NTPs) demonstrating its DNA/RNA polymerase and reverse transcriptase activity. We also show that gp577 possesses terminal transferase activity and is capable of extending ssDNA and dsDNA with NTPs and dNTPs. Mutation of the conserved primase motif residues of gp577 resulted in the loss of primase, polymerase, reverse transcriptase and terminal transferase activities. Additionally, we show that gp577 possesses translesion synthesis (TLS) activity. Mimiviral gp577 represents the first protein from an NCLDV endowed with primase, polymerase, reverse transcriptase, terminal transferase and TLS activities.
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Affiliation(s)
- Ankita Gupta
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India
| | - Shailesh B Lad
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India
| | - Pratibha P Ghodke
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India
| | - P I Pradeepkumar
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India
| | - Kiran Kondabagil
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India
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15
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Meroni A, Nava GM, Bianco E, Grasso L, Galati E, Bosio MC, Delmastro D, Muzi-Falconi M, Lazzaro F. RNase H activities counteract a toxic effect of Polymerase η in cells replicating with depleted dNTP pools. Nucleic Acids Res 2019; 47:4612-4623. [PMID: 30847483 PMCID: PMC6511917 DOI: 10.1093/nar/gkz165] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 02/25/2019] [Accepted: 03/01/2019] [Indexed: 01/27/2023] Open
Abstract
RNA:DNA hybrids are transient physiological intermediates that arise during several cellular processes such as DNA replication. In pathological situations, they may stably accumulate and pose a threat to genome integrity. Cellular RNase H activities process these structures to restore the correct DNA:DNA sequence. Yeast cells lacking RNase H are negatively affected by depletion of deoxyribonucleotide pools necessary for DNA replication. Here we show that the translesion synthesis DNA polymerase η (Pol η) plays a role in DNA replication under low deoxyribonucleotides condition triggered by hydroxyurea. In particular, the catalytic reaction performed by Pol η is detrimental for RNase H deficient cells, causing DNA damage checkpoint activation and G2/M arrest. Moreover, a Pol η mutant allele with enhanced ribonucleotide incorporation further exacerbates the sensitivity to hydroxyurea of cells lacking RNase H activities. Our data are compatible with a model in which Pol η activity facilitates the formation or stabilization of RNA:DNA hybrids at stalled replication forks. However, in a scenario where RNase H activity fails to restore DNA, these hybrids become highly toxic for cells.
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Affiliation(s)
- Alice Meroni
- Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, 20133 Milano, Italy
| | - Giulia Maria Nava
- Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, 20133 Milano, Italy
| | - Eliana Bianco
- Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, 20133 Milano, Italy
| | - Lavinia Grasso
- Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, 20133 Milano, Italy
| | - Elena Galati
- Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, 20133 Milano, Italy
| | - Maria Cristina Bosio
- Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, 20133 Milano, Italy
| | - Daria Delmastro
- Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, 20133 Milano, Italy
| | - Marco Muzi-Falconi
- Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, 20133 Milano, Italy
| | - Federico Lazzaro
- Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, 20133 Milano, Italy
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16
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Sassa A, Yasui M, Honma M. Current perspectives on mechanisms of ribonucleotide incorporation and processing in mammalian DNA. Genes Environ 2019; 41:3. [PMID: 30700998 PMCID: PMC6346524 DOI: 10.1186/s41021-019-0118-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 01/08/2019] [Indexed: 01/09/2023] Open
Abstract
Ribonucleotides, which are RNA precursors, are often incorporated into DNA during replication. Although embedded ribonucleotides in the genome are efficiently removed by canonical ribonucleotide excision repair (RER), inactivation of RER causes genomic ribonucleotide accumulation, leading to various abnormalities in cells. Mutation of genes encoding factors involved in RER is associated with the neuroinflammatory autoimmune disorder Aicardi–Goutières syndrome. Over the last decade, the biological impact of ribonucleotides in the genome has attracted much attention. In the present review, we particularly focus on recent studies that have elucidated possible mechanisms of ribonucleotide incorporation and repair and their significance in mammals.
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Affiliation(s)
- Akira Sassa
- 1Department of Biology, Graduate School of Science, Chiba University, Chiba, 263-8522 Japan
| | - Manabu Yasui
- 2Division of Genetics and Mutagenesis, National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki 210-9501 Japan
| | - Masamitsu Honma
- 2Division of Genetics and Mutagenesis, National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki 210-9501 Japan
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17
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Vaisman A, Woodgate R. Ribonucleotide discrimination by translesion synthesis DNA polymerases. Crit Rev Biochem Mol Biol 2018; 53:382-402. [PMID: 29972306 DOI: 10.1080/10409238.2018.1483889] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The well-being of all living organisms relies on the accurate duplication of their genomes. This is usually achieved by highly elaborate replicase complexes which ensure that this task is accomplished timely and efficiently. However, cells often must resort to the help of various additional "specialized" DNA polymerases that gain access to genomic DNA when replication fork progression is hindered. One such specialized polymerase family consists of the so-called "translesion synthesis" (TLS) polymerases; enzymes that have evolved to replicate damaged DNA. To fulfill their main cellular mission, TLS polymerases often must sacrifice precision when selecting nucleotide substrates. Low base-substitution fidelity is a well-documented inherent property of these enzymes. However, incorrect nucleotide substrates are not only those which do not comply with Watson-Crick base complementarity, but also those whose sugar moiety is incorrect. Does relaxed base-selectivity automatically mean that the TLS polymerases are unable to efficiently discriminate between ribonucleoside triphosphates and deoxyribonucleoside triphosphates that differ by only a single atom? Which strategies do TLS polymerases employ to select suitable nucleotide substrates? In this review, we will collate and summarize data accumulated over the past decade from biochemical and structural studies, which aim to answer these questions.
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Affiliation(s)
- Alexandra Vaisman
- a Laboratory of Genomic Integrity , National Institute of Child Health and Human Development, National Institutes of Health , Bethesda , MD , USA
| | - Roger Woodgate
- a Laboratory of Genomic Integrity , National Institute of Child Health and Human Development, National Institutes of Health , Bethesda , MD , USA
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18
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Herbert C, Dzowo YK, Urban A, Kiggins CN, Resendiz MJE. Reactivity and Specificity of RNase T 1, RNase A, and RNase H toward Oligonucleotides of RNA Containing 8-Oxo-7,8-dihydroguanosine. Biochemistry 2018; 57:2971-2983. [PMID: 29683663 DOI: 10.1021/acs.biochem.8b00277] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Understanding how oxidatively damaged RNA interacts with ribonucleases is important because of its proposed role in the development and progression of disease. Thus, understanding structural aspects of RNA containing lesions generated under oxidative stress, as well as its interactions with other biopolymers, is fundamental. We explored the reactivity of RNase A, RNase T1, and RNase H toward oligonucleotides of RNA containing 8-oxo-7,8-dihydroguanosine (8oxoG). This is the first example that addresses this relationship and will be useful for understanding (1) how these RNases can be used to characterize the structural impact that this lesion has on RNA and (2) how oxidatively modified RNA may be handled intracellularly. 8-OxoG was incorporated into 10-16-mers of RNA, and its reactivity with each ribonuclease was assessed via electrophoretic analyses, circular dichroism, and the use of other C8-purine-modified analogues (8-bromoguanosine, 8-methoxyguanosine, and 8-oxoadenosine). RNase T1 does not recognize sites containing 8-oxoG, while RNase A recognizes and cleaves RNA at positions containing this lesion while differentiating if it is involved in H-bonding. The selectivity of RNase A followed the order C > 8-oxoG ≈ U. In addition, isothermal titration calorimetry showed that an 8-oxoG-C3'-methylphosphate derivative can inhibit RNase A activity. Cleavage patterns obtained from RNase H displayed changes in reactivity in a sequence- and concentration-dependent manner and displayed recognition at sites containing the modification in some cases. These data will aid in understanding how this modification affects reactivity with ribonucleases and will enable the characterization of global and local structural changes in oxidatively damaged RNA.
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Affiliation(s)
- Cassandra Herbert
- Department of Chemistry , University of Colorado Denver , Science Building, 1151 Arapahoe Street , Denver , Colorado 80204 , United States
| | - Yannick Kokouvi Dzowo
- Department of Chemistry , University of Colorado Denver , Science Building, 1151 Arapahoe Street , Denver , Colorado 80204 , United States
| | - Anthony Urban
- Department of Chemistry , University of Colorado Denver , Science Building, 1151 Arapahoe Street , Denver , Colorado 80204 , United States
| | - Courtney N Kiggins
- Department of Chemistry , University of Colorado Denver , Science Building, 1151 Arapahoe Street , Denver , Colorado 80204 , United States
| | - Marino J E Resendiz
- Department of Chemistry , University of Colorado Denver , Science Building, 1151 Arapahoe Street , Denver , Colorado 80204 , United States
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19
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Gali VK, Balint E, Serbyn N, Frittmann O, Stutz F, Unk I. Translesion synthesis DNA polymerase η exhibits a specific RNA extension activity and a transcription-associated function. Sci Rep 2017; 7:13055. [PMID: 29026143 PMCID: PMC5638924 DOI: 10.1038/s41598-017-12915-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 09/01/2017] [Indexed: 11/09/2022] Open
Abstract
Polymerase eta (Polη) is a low fidelity translesion synthesis DNA polymerase that rescues damage-stalled replication by inserting deoxy-ribonucleotides opposite DNA damage sites resulting in error-free or mutagenic damage bypass. In this study we identify a new specific RNA extension activity of Polη of Saccharomyces cerevisiae. We show that Polη is able to extend RNA primers in the presence of ribonucleotides (rNTPs), and that these reactions are an order of magnitude more efficient than the misinsertion of rNTPs into DNA. Moreover, during RNA extension Polη performs error-free bypass of the 8-oxoguanine and thymine dimer DNA lesions, though with a 103 and 102-fold lower efficiency, respectively, than it synthesizes opposite undamaged nucleotides. Furthermore, in vivo experiments demonstrate that the transcription of several genes is affected by the lack of Polη, and that Polη is enriched over actively transcribed regions. Moreover, inactivation of its polymerase activity causes similar transcription inhibition as the absence of Polη. In summary, these results suggest that the new RNA synthetic activity of Polη can have in vivo relevance.
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Affiliation(s)
- Vamsi K Gali
- The Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, Szeged, H-6726, Hungary.,Institute of Medical Sciences Foresterhill, University of Aberdeen, Aberdeen, United Kingdom
| | - Eva Balint
- The Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, Szeged, H-6726, Hungary
| | - Nataliia Serbyn
- Department of Cell Biology, iGE3, University of Geneva, 1211, Geneva, Switzerland
| | - Orsolya Frittmann
- The Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, Szeged, H-6726, Hungary
| | - Francoise Stutz
- Department of Cell Biology, iGE3, University of Geneva, 1211, Geneva, Switzerland
| | - Ildiko Unk
- The Institute of Genetics, Biological Research Centre, Hungarian Academy of Sciences, Szeged, H-6726, Hungary.
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20
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Su Y, Egli M, Guengerich FP. Human DNA polymerase η accommodates RNA for strand extension. J Biol Chem 2017; 292:18044-18051. [PMID: 28972162 DOI: 10.1074/jbc.m117.809723] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 09/22/2017] [Indexed: 12/24/2022] Open
Abstract
Ribonucleotides are the natural analogs of deoxyribonucleotides, which can be misinserted by DNA polymerases, leading to the most abundant DNA lesions in genomes. During replication, DNA polymerases tolerate patches of ribonucleotides on the parental strands to different extents. The majority of human DNA polymerases have been reported to misinsert ribonucleotides into genomes. However, only PrimPol, DNA polymerase α, telomerase, and the mitochondrial human DNA polymerase (hpol) γ have been shown to tolerate an entire RNA strand. Y-family hpol η is known for translesion synthesis opposite the UV-induced DNA lesion cyclobutane pyrimidine dimer and was recently found to incorporate ribonucleotides into DNA. Here, we report that hpol η is able to bind DNA/DNA, RNA/DNA, and DNA/RNA duplexes with similar affinities. In addition, hpol η, as well as another Y-family DNA polymerase, hpol κ, accommodates RNA as one of the two strands during primer extension, mainly by inserting dNMPs opposite unmodified templates or DNA lesions, such as 8-oxo-2'-deoxyguanosine or cyclobutane pyrimidine dimer, even in the presence of an equal amount of the DNA/DNA substrate. The discovery of this RNA-accommodating ability of hpol η redefines the traditional concept of human DNA polymerases and indicates potential new functions of hpol η in vivo.
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Affiliation(s)
- Yan Su
- From the Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146
| | - Martin Egli
- From the Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146
| | - F Peter Guengerich
- From the Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146
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