Genomic Instability of G-Quadruplex Sequences in <i>Escherichia coli</i>: Roles of DinG, RecG, and RecQ Helicases
Guanine-rich DNA can fold into highly stable four-stranded DNA structures called G-quadruplexes (G4). Originally identified in sequences from telomeres and oncogene promoters, they can alter DNA metabolism. Indeed, G4-forming sequences represent obstacles for the DNA polymerase, with important conse...
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MDPI AG
2023-08-01
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| author | Virali J. Parekh Grzegorz Węgrzyn Véronique Arluison Richard R. Sinden |
| author_facet | Virali J. Parekh Grzegorz Węgrzyn Véronique Arluison Richard R. Sinden |
| author_sort | Virali J. Parekh |
| collection | DOAJ |
| description | Guanine-rich DNA can fold into highly stable four-stranded DNA structures called G-quadruplexes (G4). Originally identified in sequences from telomeres and oncogene promoters, they can alter DNA metabolism. Indeed, G4-forming sequences represent obstacles for the DNA polymerase, with important consequences for cell life as they may lead to genomic instability. To understand their role in bacterial genomic instability, different G-quadruplex-forming repeats were cloned into an <i>Escherichia coli</i> genetic system that reports frameshifts and complete or partial deletions of the repeat when the G-tract comprises either the leading or lagging template strand during replication. These repeats formed stable G-quadruplexes in single-stranded DNA but not naturally supercoiled double-stranded DNA. Nevertheless, transcription promoted G-quadruplex formation in the resulting R-loop for (G<sub>3</sub>T)<sub>4</sub> and (G<sub>3</sub>T)<sub>8</sub> repeats. Depending on genetic background and sequence propensity for structure formation, mutation rates varied by five orders of magnitude. Furthermore, while in vitro approaches have shown that bacterial helicases can resolve G4, it is still unclear whether G4 unwinding is important in vivo. Here, we show that a mutation in <i>recG</i> decreased mutation rates, while deficiencies in the structure-specific helicases DinG and RecQ increased mutation rates. These results suggest that G-quadruplex formation promotes genetic instability in bacteria and that helicases play an important role in controlling this process in vivo. |
| first_indexed | 2024-03-10T22:42:59Z |
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| institution | Directory Open Access Journal |
| issn | 2073-4425 |
| language | English |
| last_indexed | 2024-03-10T22:42:59Z |
| publishDate | 2023-08-01 |
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| record_format | Article |
| series | Genes |
| spelling | doaj.art-09f1d2b8b21944dabcad374df9aa194c2023-11-19T10:52:46ZengMDPI AGGenes2073-44252023-08-01149172010.3390/genes14091720Genomic Instability of G-Quadruplex Sequences in <i>Escherichia coli</i>: Roles of DinG, RecG, and RecQ HelicasesVirali J. Parekh0Grzegorz Węgrzyn1Véronique Arluison2Richard R. Sinden3Laboratory of DNA Structure and Mutagenesis, Department of Chemistry, Biology and Health Sciences, South Dakota School of Mines and Technology, Rapid City, SD 57701, USADepartment of Molecular Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, PolandLaboratoire Léon Brillouin LLB, CEA, CNRS UMR12, CEA Saclay, 91191 Gif-sur-Yvette, FranceLaboratory of DNA Structure and Mutagenesis, Department of Chemistry, Biology and Health Sciences, South Dakota School of Mines and Technology, Rapid City, SD 57701, USAGuanine-rich DNA can fold into highly stable four-stranded DNA structures called G-quadruplexes (G4). Originally identified in sequences from telomeres and oncogene promoters, they can alter DNA metabolism. Indeed, G4-forming sequences represent obstacles for the DNA polymerase, with important consequences for cell life as they may lead to genomic instability. To understand their role in bacterial genomic instability, different G-quadruplex-forming repeats were cloned into an <i>Escherichia coli</i> genetic system that reports frameshifts and complete or partial deletions of the repeat when the G-tract comprises either the leading or lagging template strand during replication. These repeats formed stable G-quadruplexes in single-stranded DNA but not naturally supercoiled double-stranded DNA. Nevertheless, transcription promoted G-quadruplex formation in the resulting R-loop for (G<sub>3</sub>T)<sub>4</sub> and (G<sub>3</sub>T)<sub>8</sub> repeats. Depending on genetic background and sequence propensity for structure formation, mutation rates varied by five orders of magnitude. Furthermore, while in vitro approaches have shown that bacterial helicases can resolve G4, it is still unclear whether G4 unwinding is important in vivo. Here, we show that a mutation in <i>recG</i> decreased mutation rates, while deficiencies in the structure-specific helicases DinG and RecQ increased mutation rates. These results suggest that G-quadruplex formation promotes genetic instability in bacteria and that helicases play an important role in controlling this process in vivo.https://www.mdpi.com/2073-4425/14/9/1720DNA repeatgenomic instabilityalternative DNA structurereplication slippagequadruplexmutagenesis |
| spellingShingle | Virali J. Parekh Grzegorz Węgrzyn Véronique Arluison Richard R. Sinden Genomic Instability of G-Quadruplex Sequences in <i>Escherichia coli</i>: Roles of DinG, RecG, and RecQ Helicases Genes DNA repeat genomic instability alternative DNA structure replication slippage quadruplex mutagenesis |
| title | Genomic Instability of G-Quadruplex Sequences in <i>Escherichia coli</i>: Roles of DinG, RecG, and RecQ Helicases |
| title_full | Genomic Instability of G-Quadruplex Sequences in <i>Escherichia coli</i>: Roles of DinG, RecG, and RecQ Helicases |
| title_fullStr | Genomic Instability of G-Quadruplex Sequences in <i>Escherichia coli</i>: Roles of DinG, RecG, and RecQ Helicases |
| title_full_unstemmed | Genomic Instability of G-Quadruplex Sequences in <i>Escherichia coli</i>: Roles of DinG, RecG, and RecQ Helicases |
| title_short | Genomic Instability of G-Quadruplex Sequences in <i>Escherichia coli</i>: Roles of DinG, RecG, and RecQ Helicases |
| title_sort | genomic instability of g quadruplex sequences in i escherichia coli i roles of ding recg and recq helicases |
| topic | DNA repeat genomic instability alternative DNA structure replication slippage quadruplex mutagenesis |
| url | https://www.mdpi.com/2073-4425/14/9/1720 |
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