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Siters KE, Sander SA, Devlin JR, Morrow JR. Bifunctional Zn(II) complexes for recognition of non-canonical thymines in DNA bulges and G-quadruplexes. Dalton Trans 2015; 44:3708-16. [PMID: 25521076 DOI: 10.1039/c4dt03004d] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Six Zn(II) complexes of derivatives of 1,4,7,10-tetraazacyclododecane (cyclen) were studied for binding to DNA sequences containing non-canonical thymines, including a hairpin with a single thymine bulge (T-bulge) and a G-quadruplex (H-telo) containing thymine loops. The cyclen-based macrocycles contained pendents with either two fused rings to give planar groups including quinolinone (QMC), coumarin (MCC) and quinoline (CQC) derivatives or a non-planar dansyl group (DSC). Macrocyclic complexes with three fused rings including an anthraquinone pendent (ATQ) were also studied. All Zn(II) complexes were stable in solution at micromolar concentrations and neutral pH with the Zn(L)(OH2) species prevailing for L = QMC and CQC at pH 7.5 and 100 mM NaCl. Immobilized T-bulge or H-telo G-quadruplex was used to study binding of the complexes by surface plasmon resonance (SPR) for several of the complexes. For the most part, data matched well with that obtained by isothermal calorimetry (ITC) and, for fluorescent complexes, by fluorescence titrations. Data showed that Zn(II) complexes containing planar aromatic pendents with two fused rings bound to T-bulge more tightly than complexes with non-planar pendents such as DSC. The H-telo DNA exhibited multiple binding sites for all complexes containing aromatic pendents. The complexes with two fused rings bound with low micromolar dissociation constants and two binding sites whereas a complex with three fused rings (ATQ) bound to three sites. This study shows that different pendent groups on Zn(II) cyclen complexes impart selectivity for recognition of non-canonical DNA structures.
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Affiliation(s)
- Kevin E Siters
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260, USA.
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Peng J, Shao Y, Liu L, Zhang L, Liu H. Specific recognition of DNA bulge sites by in situ grown fluorescent Ag nanoclusters with high selectivity. Dalton Trans 2014; 43:1534-41. [DOI: 10.1039/c3dt52042k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Chi LM, Lam SL. Sequence context effect on strand slippage in natural DNA primer-templates. J Phys Chem B 2012; 116:1999-2007. [PMID: 22304666 DOI: 10.1021/jp211666k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Strand slippage has been found to occur in primer-templates containing a templating thymine, cytosine, and guanine, leading to the formation of misaligned structures with a single-nucleotide bulge. If remained in the active site of low-fidelity polymerases during DNA replication, these misaligned structures can ultimately bring about deletion mutations. In this study, we performed NMR investigations on primer-template models containing a templating adenine. Similar to our previous results on guanine, adenine templates are also less prone to strand slippage than pyrimidine templates. Misalignment occurs only in primer-templates that form a terminal C·G or G·C base pair. Together with our previous findings on thymine, cytosine, and guanine templates, the present study reveals strand slippage can occur in any kind of natural templating bases during DNA replication, providing insights into the origin of mutation hotspots in natural DNA sequences. In addition to the type of incoming base upon misincorporation, the propensity of strand slippage in primer-templates depends also on the type of templating base, its upstream and downstream bases.
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Affiliation(s)
- Lai Man Chi
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
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del Mundo IMA, Fountain MA, Morrow JR. Recognition of thymine in DNA bulges by a Zn(II) macrocyclic complex. Chem Commun (Camb) 2011; 47:8566-8. [PMID: 21706105 DOI: 10.1039/c1cc12074c] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
A Zn(II) macrocyclic complex with appended quinoline is a bifunctional recognition agent that uses both the Zn(II) center and the pendent aromatic group to bind to thymine in bulges with good selectivity over DNA containing G, C or A bulges. Spectroscopic studies show that the stem containing the bulge stays largely intact in a DNA hairpin with the Zn(II) complex bound to the thymine bulge.
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Affiliation(s)
- Imee Marie A del Mundo
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY, USA
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Cappadocia L, Maréchal A, Parent JS, Lepage É, Sygusch J, Brisson N. Crystal structures of DNA-Whirly complexes and their role in Arabidopsis organelle genome repair. THE PLANT CELL 2010; 22:1849-67. [PMID: 20551348 PMCID: PMC2910959 DOI: 10.1105/tpc.109.071399] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Revised: 05/13/2010] [Accepted: 05/25/2010] [Indexed: 05/18/2023]
Abstract
DNA double-strand breaks are highly detrimental to all organisms and need to be quickly and accurately repaired. Although several proteins are known to maintain plastid and mitochondrial genome stability in plants, little is known about the mechanisms of DNA repair in these organelles and the roles of specific proteins. Here, using ciprofloxacin as a DNA damaging agent specific to the organelles, we show that plastids and mitochondria can repair DNA double-strand breaks through an error-prone pathway similar to the microhomology-mediated break-induced replication observed in humans, yeast, and bacteria. This pathway is negatively regulated by the single-stranded DNA (ssDNA) binding proteins from the Whirly family, thus indicating that these proteins could contribute to the accurate repair of plant organelle genomes. To understand the role of Whirly proteins in this process, we solved the crystal structures of several Whirly-DNA complexes. These reveal a nonsequence-specific ssDNA binding mechanism in which DNA is stabilized between domains of adjacent subunits and rendered unavailable for duplex formation and/or protein interactions. Our results suggest a model in which the binding of Whirly proteins to ssDNA would favor accurate repair of DNA double-strand breaks over an error-prone microhomology-mediated break-induced replication repair pathway.
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Chi LM, Lam SL. NMR investigation of DNA primer-template models: guanine templates are less prone to strand slippage upon misincorporation. Biochemistry 2009; 48:11478-86. [PMID: 19886640 DOI: 10.1021/bi9014049] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Misaligned structures can result from strand slippage during DNA replication and, if not repaired, would lead to mutations. Previously, we showed that strand slippage can occur upon misincorporation of a dNTP opposite thymine and cytosine templates, resulting in a misaligned structure with a T- or C-bulge. The formation propensity for misaligned structures was found to depend on the type of terminal base pair. In this study, we performed NMR investigations on primer-template models containing a guanine template. Our results reveal guanine templates are less prone to strand slippage than pyrimidine templates. Misalignment was found to occur only in 5'-CG templates with a downstream purine. In addition to the significance of terminal base pair and upstream nucleotide, the present study reveals the importance of the templating base and its downstream nucleotide, which also determine the propensity of strand slippage in primer-templates.
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Affiliation(s)
- Lai Man Chi
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
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A microhomology-mediated break-induced replication model for the origin of human copy number variation. PLoS Genet 2009; 5:e1000327. [PMID: 19180184 PMCID: PMC2621351 DOI: 10.1371/journal.pgen.1000327] [Citation(s) in RCA: 615] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Chromosome structural changes with nonrecurrent endpoints associated with genomic disorders offer windows into the mechanism of origin of copy number variation (CNV). A recent report of nonrecurrent duplications associated with Pelizaeus-Merzbacher disease identified three distinctive characteristics. First, the majority of events can be seen to be complex, showing discontinuous duplications mixed with deletions, inverted duplications, and triplications. Second, junctions at endpoints show microhomology of 2–5 base pairs (bp). Third, endpoints occur near pre-existing low copy repeats (LCRs). Using these observations and evidence from DNA repair in other organisms, we derive a model of microhomology-mediated break-induced replication (MMBIR) for the origin of CNV and, ultimately, of LCRs. We propose that breakage of replication forks in stressed cells that are deficient in homologous recombination induces an aberrant repair process with features of break-induced replication (BIR). Under these circumstances, single-strand 3′ tails from broken replication forks will anneal with microhomology on any single-stranded DNA nearby, priming low-processivity polymerization with multiple template switches generating complex rearrangements, and eventual re-establishment of processive replication.
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Dash C, Scarth BJ, Badorrek C, Götte M, Le Grice SFJ. Examining the ribonuclease H primer grip of HIV-1 reverse transcriptase by charge neutralization of RNA/DNA hybrids. Nucleic Acids Res 2008; 36:6363-71. [PMID: 18836193 PMCID: PMC2582618 DOI: 10.1093/nar/gkn678] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The crystal structure of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) bound to an RNA/DNA hybrid reveals an extensive network of contacts with the phosphate backbone of the DNA strand ∼4–9 bp downstream from the ribonuclease H (RNase H) catalytic center. Collectively designated as ‘the RNase H primer grip’, this motif contains a phosphate binding pocket analogous to the human and Bacillus halodurans RNases H. The notion that the RNase H primer grip mediates the trajectory of RNA/DNA hybrids accessing the RNase H active site suggests that locally neutralizing the phosphate backbone may be exploited to manipulate nucleic acid flexibility. To examine this, we introduced single and tandem methylphosphonate substitutions through the region of the DNA primer contacted by the RNase H primer grip and into the RNase H catalytic center. The ability of mutant hybrids to support RNase H and DNA polymerase activity was thereafter examined. In addition, site-specific chemical footprinting was used to evaluate movement of the DNA polymerase and RNase H domains. We show here that minor alteration to the RNase H primer can have a dramatic effect on enzyme positioning, and discuss these findings in light of recent crystallography of human RNase H containing an RNA/DNA hybrid.
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Affiliation(s)
- Chandravanu Dash
- HIV Drug Resistance Program, National Cancer Institute at Frederick, Frederick, MD 21702, USA
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Fang H, Taylor JS. Serial analysis of mutation spectra (SAMS): a new approach for the determination of mutation spectra of site-specific DNA damage and their sequence dependence. Nucleic Acids Res 2008; 36:6004-12. [PMID: 18812400 PMCID: PMC2566868 DOI: 10.1093/nar/gkn595] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Many mutations occur as a result of DNA synthesis past the site of DNA damage by DNA damage bypass polymerases. The frequency and types of mutations not only depend on the nature of the damage, but also on the sequence context, as revealed from analysis of mutation spectra of DNA exposed to mutagens. Herein we report a new method for the rapid determination of the effect of sequence context on mutagenesis called SAMS for serial analysis of mutation spectra. This technique makes use of the methodology that underlies serial analysis of gene expression (SAGE) to analyze mutations that result from DNA synthesis past a DNA lesion site-specifically embedded in a library of DNA sequences. To illustrate our technique we determined the effect of sequence context on mutations generated by DNA synthesis past a tetrahydrofuran abasic site model by the DNA damage bypass polymerase yeast polymerase η.
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Affiliation(s)
- Huafeng Fang
- Department of Chemistry, Washington University, St Louis, MO, USA
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Chi LM, Lam SL. Nuclear magnetic resonance investigation of primer--template models: formation of a pyrimidine bulge upon misincorporation. Biochemistry 2008; 47:4469-76. [PMID: 18358004 DOI: 10.1021/bi8001456] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Our previous studies have shown that misaligned structures can occur upon misincorporation of a dNTP opposite thymine templates. The formation of misaligned structures during DNA replication, if not repaired properly, can be bypassed and extended by low-fidelity polymerases and ultimately lead to mutations. In this study, the base pair structures at the replicating sites of a set of primer-template models which mimic the situation upon misincorporation of a dNTP opposite cytosine templates have been determined. High-resolution NMR structural results show that misaligned structures with a C-bulge can be formed upon incorporation of dCTP, dTTP, and dATP opposite 5'-GC, 5'-AC, and 5'-TC templates, respectively. The stabilities of misaligned structures depend on the types of terminal base pairs at the replicating sites. Together with the structural findings in thymine templates, we conclude that terminal G.C and C.G base pairs always contribute a larger stabilizing effect to the misaligned structures containing a pyrimidine bulge than terminal A.T and T.A base pairs. Misalignment and thus deletion mutation are more likely to occur if misincorporation of a nucleotide opposite a pyrimidine template can cause template slippage to form a terminal G.C or C.G base pair. Although misalignment also occurs when the newly formed terminal base pair is an A.T base pair or a T.A base pair, both misaligned and mismatched conformers coexist, which can lead to deletion and substitution mutations, respectively.
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Affiliation(s)
- Lai Man Chi
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
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Chi LM, Lam SL. NMR investigation of primer-template models: structural effect of sequence downstream of a thymine template on mutagenesis in DNA replication. Biochemistry 2007; 46:9292-300. [PMID: 17658896 DOI: 10.1021/bi700865e] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Misaligned structures can occur in primer-templates during DNA replication, which can be bypassed and extended by low-fidelity polymerases and ultimately lead to mutations. In this study, we have investigated how the nucleotide downstream of a thymine template affects the primer-template structures upon misincorporation of dNTPs. The base pair structures at the replicating sites of a set of primer-template models containing either a G or an A downstream of the thymine template have been determined using NMR spectroscopy. Incorporation of dCTP and dTTP opposite 5'-GT and 5'-AT templates, respectively, can result in misaligned structures with a T-bulge. Depending on the downstream sequence, subsequent extension of the primers may stabilize the misaligned structures or cause the formation of mismatched structures. These results provide alternative pathways for base substitution and deletion errors during DNA replication by low-fidelity polymerases.
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Affiliation(s)
- Lai Man Chi
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
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