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Gao S, Tahara Y, Kool ET, Greenberg MM. Promoter dependent RNA polymerase II bypass of the epimerizable DNA lesion, Fapy•dG and 8-Oxo-2'-deoxyguanosine. Nucleic Acids Res 2024:gkae529. [PMID: 38908029 DOI: 10.1093/nar/gkae529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2024] [Revised: 05/30/2024] [Accepted: 06/10/2024] [Indexed: 06/24/2024] Open
Abstract
Formamidopyrimidine (Fapy•dG) is a major lesion arising from oxidation of dG that is produced from a common chemical precursor of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OxodGuo). In human cells, replication of single-stranded shuttle vectors containing Fapy•dG is more mutagenic than 8-OxodGuo. Here, we present the first data regarding promoter dependent RNA polymerase II bypass of Fapy•dG. 8-OxodGuo bypass was examined side-by-side. Experiments were carried out using double-stranded shuttle vectors in HeLa cell nuclear lysates and in HEK 293T cells. The lesions do not significantly block transcriptional bypass efficiency. Less than 2% adenosine incorporation occurred in cells when the lesions were base paired with dC. Inhibiting base excision repair in HEK 293T cells significantly increased adenosine incorporation, particularly from Fapy•dG:dC bypass which yielded ∼25% adenosine incorporation. No effect was detected upon transcriptional bypass of either lesion in nucleotide excision repair deficient cells. Transcriptional mutagenesis was significantly higher when shuttle vectors containing dA opposite one of the lesions were employed. For Fapy•dG:dA bypass, adenosine incorporation was greater than 85%; whereas 8-OxodGuo:dA yielded >20% point mutations. The combination of more frequent replication mistakes and greater error-prone Pol II bypass suggest that Fapy•dG is more mutagenic than 8-OxodGuo.
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Affiliation(s)
- Shijun Gao
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Yuki Tahara
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Eric T Kool
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Marc M Greenberg
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
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Gao S, Guan H, Bloomer H, Wich D, Song D, Khirallah J, Ye Z, Zhao Y, Chen M, Xu C, Liu L, Xu Q. Harnessing non-Watson-Crick's base pairing to enhance CRISPR effectors cleavage activities and enable gene editing in mammalian cells. Proc Natl Acad Sci U S A 2024; 121:e2308415120. [PMID: 38150477 PMCID: PMC10786293 DOI: 10.1073/pnas.2308415120] [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: 05/19/2023] [Accepted: 11/21/2023] [Indexed: 12/29/2023] Open
Abstract
Genomic DNA of the cyanophage S-2L virus is composed of 2-aminoadenine (Z), thymine (T), guanine (G), and cytosine (C), forming the genetic alphabet ZTGC, which violates Watson-Crick base pairing rules. The Z-base has an extra amino group on the two position that allows the formation of a third hydrogen bond with thymine in DNA strands. Here, we explored and expanded applications of this non-Watson-Crick base pairing in protein expression and gene editing. Both ZTGC-DNA (Z-DNA) and ZUGC-RNA (Z-RNA) produced in vitro show detectable compatibility and can be decoded in mammalian cells, including Homo sapiens cells. Z-crRNA can guide CRISPR-effectors SpCas9 and LbCas12a to cleave specific DNA through non-Watson-Crick base pairing and boost cleavage activities compared to A-crRNA. Z-crRNA can also allow for efficient gene and base editing in human cells. Together, our results help pave the way for potential strategies for optimizing DNA or RNA payloads for gene editing therapeutics and give insights to understanding the natural Z-DNA genome.
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Affiliation(s)
- Shuliang Gao
- Department of Biomedical Engineering, Tufts University, Medford, MA02155
| | - Huiwen Guan
- Department of Biomedical Engineering, Tufts University, Medford, MA02155
| | - Hanan Bloomer
- Department of Biomedical Engineering, Tufts University, Medford, MA02155
| | - Douglas Wich
- Department of Biomedical Engineering, Tufts University, Medford, MA02155
| | - Donghui Song
- Department of Biomedical Engineering, Tufts University, Medford, MA02155
| | - Jennifer Khirallah
- Department of Biomedical Engineering, Tufts University, Medford, MA02155
| | - Zhongfeng Ye
- Department of Biomedical Engineering, Tufts University, Medford, MA02155
| | - Yu Zhao
- Department of Biomedical Engineering, Tufts University, Medford, MA02155
| | - Mengting Chen
- Department of Biomedical Engineering, Tufts University, Medford, MA02155
| | - Chutian Xu
- Department of Biomedical Engineering, Tufts University, Medford, MA02155
| | - Lihan Liu
- Department of Biomedical Engineering, Tufts University, Medford, MA02155
| | - Qiaobing Xu
- Department of Biomedical Engineering, Tufts University, Medford, MA02155
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Zhang M, Singh N, Ehmann ME, Zheng L, Zhao H. Incorporation of noncanonical base Z yields modified mRNA with minimal immunogenicity and improved translational capacity in mammalian cells. iScience 2023; 26:107739. [PMID: 37720088 PMCID: PMC10504480 DOI: 10.1016/j.isci.2023.107739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Revised: 07/18/2023] [Accepted: 08/23/2023] [Indexed: 09/19/2023] Open
Abstract
Chemically modified mRNAs hold great potential for therapeutic applications in vivo. Currently, the base modification scheme largely preserves the canonical Watson-Crick base pairing, thus missing one mode of mRNA modulation by altering its secondary structure. Here we report the incorporation of base Z (2-aminoadenine) into mRNA to create Z-mRNA with improved translational capacity, decreased cytotoxicity, and drastically reduced immunogenicity compared to the unmodified mRNA in mammalian cells. In particular, the A-to-Z substitution renders modified mRNAs less immunogenic than the state-of-the-art base modification N1-methylpseudouridine (m1ψ) in mouse embryonic fibroblast cells. As a proof of concept, we developed a Z-mRNA-based vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Antigen-encoding Z-mRNA elicited substantial humoral and cellular immune responses in vivo in mice, albeit with relatively lower efficacy than the state-of-the-art m1ψ-mRNA. Z-mRNA expands the scope of mRNA base modifications toward noncanonical bases and could offer an advantageous platform for mRNA-based therapeutics where minimal immunogenicity is desired.
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Affiliation(s)
- Meng Zhang
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Nilmani Singh
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Mary Elisabeth Ehmann
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Lining Zheng
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Huimin Zhao
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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Fleming AM, Burrows CJ. Nanopore sequencing for N1-methylpseudouridine in RNA reveals sequence-dependent discrimination of the modified nucleotide triphosphate during transcription. Nucleic Acids Res 2023; 51:1914-1926. [PMID: 36727474 PMCID: PMC9976907 DOI: 10.1093/nar/gkad044] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 12/21/2022] [Accepted: 01/16/2023] [Indexed: 02/03/2023] Open
Abstract
Direct RNA sequencing with a commercial nanopore platform was used to sequence RNA containing uridine (U), pseudouridine (Ψ) or N1-methylpseudouridine (m1Ψ) in >100 different 5-nucleotide contexts. The base calling data for Ψ or m1Ψ were similar but different from U allowing their detection. Understanding the nanopore signatures for Ψ and m1Ψ enabled a running start T7 RNA polymerase assay to study the selection of UTP versus ΨTP or m1ΨTP competing mixtures in all possible adjacent sequence contexts. A significant sequence context dependency was observed for T7 RNA polymerase with insertion yields for ΨTP versus UTP spanning a range of 20-65%, and m1ΨTP versus UTP producing variable yields that differ by 15-70%. Experiments with SP6 RNA polymerase, as well as chemically-modified triphosphates and DNA templates provide insight to explain the observations. The SP6 polymerase introduced m1ΨTP when competed with UTP with a smaller window of yields (15-30%) across all sequence contexts studied. These results may aid in future efforts that employ RNA polymerases to make therapeutic mRNAs with sub-stoichiometric amounts of m1Ψ.
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Affiliation(s)
- Aaron M Fleming
- Dept. of Chemistry, University of Utah, Salt Lake City, UT 84112-0850, USA
| | - Cynthia J Burrows
- Dept. of Chemistry, University of Utah, Salt Lake City, UT 84112-0850, USA
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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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Yang Y, Wang Z, Wang J, Dai X, You C. Next-Generation Sequencing-Based Analysis of the Effects of N1- and N6-Methyldeoxyadenosine Adducts on DNA Transcription. Anal Chem 2022; 94:11248-11254. [PMID: 35924299 DOI: 10.1021/acs.analchem.2c01764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
DNA methylation can occur naturally or be induced by various environmental and chemotherapeutic agents. The regioisomeric N1- and N6-methyldeoxyadenosine (1mdA and 6mdA, respectively) represent an important class of methylated DNA adducts. In this study, we developed a shuttle vector- and next-generation sequencing-based assay to quantitatively assess the effects of 1mdA and 6mdA on the accuracy and efficiency of DNA transcription. Our results revealed that 1mdA can induce multiple types of mutant transcripts and strongly inhibit DNA transcription, whereas 6mdA is a nonmutagenic DNA adduct that can exhibit a subtle but significant inhibitory effect on DNA transcription in vitro and in human cells. Moreover, our results demonstrated that the transcription-coupled nucleotide excision repair pathway is dispensable for the removal of 1mdA and 6mdA from the template DNA strand in human cells. These findings provided new important insights into the functional interplay between DNA methylation modifications and transcription in mammalian cells.
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Affiliation(s)
- Ying Yang
- Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, Institute of Chemical Biology and Nanomedicine, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Ziyu Wang
- Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, Institute of Chemical Biology and Nanomedicine, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Juan Wang
- Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, Institute of Chemical Biology and Nanomedicine, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Xiaoxia Dai
- Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, Institute of Chemical Biology and Nanomedicine, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Changjun You
- Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, Institute of Chemical Biology and Nanomedicine, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
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