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Jastrzębska K, Maciaszek A, Dolot R, Tomaszewska-Antczak A, Mikołajczyk B, Guga P. Synthesis and hybridizing properties of P-stereodefined chimeric [PS]-{DNA:RNA} and [PS]-{DNA:(2'-OMe)-RNA} oligomers. RSC Adv 2022; 12:26815-26824. [PMID: 36320848 PMCID: PMC9491215 DOI: 10.1039/d2ra04855h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Accepted: 09/08/2022] [Indexed: 11/22/2022] Open
Abstract
Oxathiaphospholane derivatives of 2'-OMe-ribonucleosides and 2'-O-TBDMS-ribonucleosides (MN-OTP and TN-OTP, respectively; nucleobase protected) were synthesized and separated into pure P-diastereomers. X-ray analysis showed the R P absolute configuration of the phosphorus atom in the fast-eluting diastereomer of TA-OTP. The fast- and slow-eluting P-diastereomers of MN-OTP and TN-OTP were used in the solid-phase synthesis of phosphorothioate dinucleotides (MNPST and NPST, respectively), which were subsequently hydrolyzed with R P-selective phosphodiesterase svPDE and S P-selective nuclease P1 to determine the absolute configuration of the phosphorus atoms. P-Stereodefined phosphorothioate ([PS]) 10-mer chimeric oligomers [PS]-{DNA:(2'-OMe)-RNA} and isosequential [PS]-{DNA:RNA} containing two MNPS or NPS units were synthesized. Melting experiments performed for their complexes with Watson-Crick paired DNA matrix showed that MNPS or NPS units decrease the thermal stability of the duplexes (ΔT m = -0.5 ÷ -5.5 °C per modification) regardless of the absolute configuration of the P-atoms. When the (2'-OMe)-RNA matrix was used an increase in T m was noted in all cases (ΔT m = +1 ÷ +7 °C per modification). The changes in thermal stability of the duplexes formed by [PS]-chimeras with DNA and (2'-OMe)-RNA matrices do not correlate with the absolute configuration of the phosphorus atoms.
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Affiliation(s)
- Katarzyna Jastrzębska
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry Sienkiewicza 112. 90-363 Łódź Poland +48-42-6803261 +48-42-6803248
| | - Anna Maciaszek
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry Sienkiewicza 112. 90-363 Łódź Poland +48-42-6803261 +48-42-6803248
| | - Rafał Dolot
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry Sienkiewicza 112. 90-363 Łódź Poland +48-42-6803261 +48-42-6803248
| | - Agnieszka Tomaszewska-Antczak
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry Sienkiewicza 112. 90-363 Łódź Poland +48-42-6803261 +48-42-6803248
| | - Barbara Mikołajczyk
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry Sienkiewicza 112. 90-363 Łódź Poland +48-42-6803261 +48-42-6803248
| | - Piotr Guga
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry Sienkiewicza 112. 90-363 Łódź Poland +48-42-6803261 +48-42-6803248
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Radzikowska E, Kaczmarek R, Korczyński D, Krakowiak A, Mikołajczyk B, Baraniak J, Guga P, Wheeler KA, Pawlak T, Nawrot B. P-stereocontrolled synthesis of oligo(nucleoside N3'→O5' phosphoramidothioate)s - opportunities and limitations. RSC Adv 2020; 10:35185-35197. [PMID: 35515667 PMCID: PMC9056831 DOI: 10.1039/d0ra04987e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 09/15/2020] [Indexed: 12/29/2022] Open
Abstract
3'-N-(2-Thio-1,3,2-oxathiaphospholane) derivatives of 5'-O-DMT-3'-amino-2',3'-dideoxy-ribonucleosides (NOTP-N), that bear a 4,4-unsubstituted, 4,4-dimethyl, or 4,4-pentamethylene substituted oxathiaphospholane ring, were synthesized. Within these three series, NOTP-N differed by canonical nucleobases (i.e., AdeBz, CytBz, GuaiBu, or Thy). The monomers were chromatographically separated into P-diastereomers, which were further used to prepare NNPSN' dinucleotides (3), as well as short P-stereodefined oligo(deoxyribonucleoside N3'→O5' phosphoramidothioate)s (NPS-) and chimeric NPS/PO- and NPS/PS-oligomers. The condensation reaction for NOTP-N monomers was found to be 5-6 times slower than the analogous OTP derivatives. When the 5'-end nucleoside of a growing oligomer adopts a C3'-endo conformation, a conformational 'clash' with the incoming NOTP-N monomer takes place, which is a main factor decreasing the repetitive yield of chain elongation. Although both isomers of NNPSN' were digested by the HINT1 phosphoramidase enzyme, the isomers hydrolyzed at a faster rate were tentatively assigned the R P absolute configuration. This assignment is supported by X-ray analysis of the protected dinucleotide DMTdGiBu NPSMeTOAc, which is P-stereoequivalent to the hydrolyzed faster P-diastereomer of dGNPST.
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Affiliation(s)
- Ewa Radzikowska
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences Sienkiewicza 112 90-363 Łódź Poland
| | - Renata Kaczmarek
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences Sienkiewicza 112 90-363 Łódź Poland
| | - Dariusz Korczyński
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences Sienkiewicza 112 90-363 Łódź Poland
| | - Agnieszka Krakowiak
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences Sienkiewicza 112 90-363 Łódź Poland
| | - Barbara Mikołajczyk
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences Sienkiewicza 112 90-363 Łódź Poland
| | - Janina Baraniak
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences Sienkiewicza 112 90-363 Łódź Poland
| | - Piotr Guga
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences Sienkiewicza 112 90-363 Łódź Poland
| | - Kraig A Wheeler
- Whitworth University, Department of Chemistry 300 W. Hawthorne Rd. Spokane WA 99251 USA
| | - Tomasz Pawlak
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences Sienkiewicza 112 90-363 Łódź Poland
| | - Barbara Nawrot
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences Sienkiewicza 112 90-363 Łódź Poland
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Jastrzębska K, Mikołajczyk B, Guga P. LNA units present in [ R P-PS]-(DNA#LNA) chimeras enhance the thermal stability of parallel duplexes and triplexes formed with (2'-OMe)-RNA strands. RSC Adv 2020; 10:22370-22376. [PMID: 35514591 PMCID: PMC9054617 DOI: 10.1039/d0ra03934a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 05/28/2020] [Indexed: 11/21/2022] Open
Abstract
The results of CD measurements indicate that 2-4 LNA units distributed along 12 nt P-stereodefined phosphorothioate [R P-PS]-(DNA#LNA) chimeras impose a C3'-endo conformation on the 2'-deoxyribonucleosides. Under neutral and slightly acidic conditions homopurine [R p-PS]-(DNA#LNA) hybridizes with 9-12 nt Hoogsteen-paired (2'-OMe)-RNA strands to form parallel duplexes, which are thermally more stable than the reported earlier analogous complexes containing LNA-free [R P-PS]-DNA oligomers (ΔT m = 7 °C per LNA unit at pH 5.4). Upon addition of the corresponding Watson-Crick-paired (2'-OMe)-RNA strands, parallel triplexes are formed with further increased thermal stability.
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Affiliation(s)
- Katarzyna Jastrzębska
- Department of Bioorganic Chemistry, Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences Sienkiewicza 112 90-363 Łódź Poland
| | - Barbara Mikołajczyk
- Department of Bioorganic Chemistry, Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences Sienkiewicza 112 90-363 Łódź Poland
| | - Piotr Guga
- Department of Bioorganic Chemistry, Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences Sienkiewicza 112 90-363 Łódź Poland
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Maciaszek A, Jastrzębska K, Guga P. Homopurine R P-stereodefined phosphorothioate analogs of DNA with hampered Watson-Crick base pairings form Hoogsteen paired parallel duplexes with (2'-OMe)-RNAs. Org Biomol Chem 2019; 17:4611-4620. [PMID: 31017142 DOI: 10.1039/c8ob03112f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
3'-O-(2-Thio-4,4-pentamethylene-1,3,2-oxathiaphospholane) derivatives of 5'-O-DMT-N6-methyl-deoxyadenosine and 5'-O-DMT-N2,N2-dimethyl-O6-diphenylcarbamoyl-deoxyguanosine (OTP-NY, NY = DMT-m6dA or DMT-m,m2dGDPC) were synthesized, resolved onto pure P-diastereomers, and used in P-stereocontrolled synthesis of dinucleoside 3',5,-phosphorothioates NXPST (NX = m6dA or m,m2dG), in which the absolute configuration of the stereogenic phosphorus atom was established enzymatically. Diastereomerically pure OTP-NY and standard OTP-N (N = DMT-dABz or DMT-dGBz,DPC) were used in the synthesis of chimeric RP-stereodefined phosphorothioate oligomers ((RP-PS)-DN(NX)A) with hampered Watson-Crick base pairings. It was found that the m6dA units slightly reduce the thermodynamic stability of antiparallel duplexes formed with RNA and (2'-OMe)-RNA matrices, whereas m,m2dG units prevent their formation. The m6dA units stabilize (by up to 4.5 °C per modified unit) the parallel duplexes formed by (RP-PS)-DN(NX)A with Hoogsteen-paired (2'-OMe)-RNA templates compared to the analogous reference duplex containing only unmodified nucleobases. In contrast, the m,m2dG units destabilize such duplexes by up to 3 °C per modified unit. Both units prevent the formation of the corresponding parallel triplexes.
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Affiliation(s)
- Anna Maciaszek
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry, Sienkiewicza 112, 90-363 Łódź, Poland.
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Tomaszewska-Antczak A, Jastrzębska K, Maciaszek A, Mikołajczyk B, Guga P. P-Stereodefined phosphorothioate analogs of glycol nucleic acids-synthesis and structural properties. RSC Adv 2018; 8:24942-24952. [PMID: 35542141 PMCID: PMC9082371 DOI: 10.1039/c8ra05568h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 07/02/2018] [Indexed: 11/21/2022] Open
Abstract
Enantiomerically pure, protected acyclic nucleosides of the GNA type (glycol nucleic acids) (GN'), obtained from (R)-(+)- and (S)-(-)-glycidols and the four canonical DNA nucleobases (Ade, Cyt, Gua and Thy), were transformed into 3'-O-DMT-protected 2-thio-4,4-pentamethylene-1,3,2-oxathiaphospholane derivatives (OTP-GN') containing a second stereogenic center at the phosphorus atom. These monomers were chromatographically separated into P-diastereoisomers, which were further used for the synthesis of P-stereodefined "dinucleoside" phosphorothioates GNPST (GN = GA, GC, GG, GT). The absolute configuration at the phosphorus atom for all eight GNPST was established enzymatically and verified chemically, and correlated with chromatographic mobility of the OTP-GN' monomers on silica gel. The GNPS units (derived from (R)-(+)-glycidol) were introduced into self-complementary PS-(DNA/GNA) octamers of preselected, uniform absolute configuration at P-atoms. Thermal dissociation experiments showed that the thermodynamic stability of the duplexes depends on the stereochemistry of the phosphorus centers and relative arrangement of the GN units in the oligonucleotide strands. These results correlate with the changes of conformation assessed from circular dichroism spectra.
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Affiliation(s)
- Agnieszka Tomaszewska-Antczak
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry Sienkiewicza 112 90-363 Łódź Poland
| | - Katarzyna Jastrzębska
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry Sienkiewicza 112 90-363 Łódź Poland
| | - Anna Maciaszek
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry Sienkiewicza 112 90-363 Łódź Poland
| | - Barbara Mikołajczyk
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry Sienkiewicza 112 90-363 Łódź Poland
| | - Piotr Guga
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry Sienkiewicza 112 90-363 Łódź Poland
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Szabat M, Kierzek R. Parallel-stranded DNA and RNA duplexes - structural features and potential applications. FEBS J 2017; 284:3986-3998. [DOI: 10.1111/febs.14187] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 06/20/2017] [Accepted: 07/26/2017] [Indexed: 12/21/2022]
Affiliation(s)
- Marta Szabat
- Institute of Bioorganic Chemistry; Polish Academy of Sciences; Poznan Poland
| | - Ryszard Kierzek
- Institute of Bioorganic Chemistry; Polish Academy of Sciences; Poznan Poland
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Maciaszek A, Krakowiak A, Janicka M, Tomaszewska-Antczak A, Sobczak M, Mikołajczyk B, Guga P. LNA units present in the (2'-OMe)-RNA strand stabilize parallel duplexes (2'-OMe)-RNA/[All-R(P)-PS]-DNA and parallel triplexes (2'-OMe)-RNA/[All-R(P)-PS]-DNA/RNA. An improved tool for the inhibition of reverse transcription. Org Biomol Chem 2015; 13:2375-84. [PMID: 25564351 DOI: 10.1039/c4ob02364a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Homopurine phosphorothioate analogs of DNA, possessing all phosphorus atoms of RP configuration ([All-RP-PS]-DNA), when interact with appropriate complementary RNA or (2'-OMe)-RNA templates, form parallel triplexes or parallel duplexes of very high thermodynamic stability. The present results show that T-LNA or 5-Me-C-LNA units introduced into the parallel Hoogsteen-paired (2'-OMe)-RNA strands (up to four units in the oligomers of 9 or 12 nt in length) stabilize these parallel complexes. At neutral pH, dodecameric parallel duplexes have Tm values of 62-68 °C, which are by 4-10 °C higher than Tm for the reference duplex (with no LNA units present), while for the corresponding triplexes, Tm values exceeded 85 °C. For nonameric parallel duplexes, melting temperatures of 38-62 °C were found and (2'-OMe)-RNA oligomers containing 5-Me-C-LNA units stabilized the complexes more efficiently than the T-LNA containing congeners. In both series the stability of the parallel complexes increased with an increasing number of LNA units present. The same trend was observed in experiments of reverse transcription RNA→DNA (using AMV RT reverse transcriptase) where the formation of parallel triplexes (consisting of an RNA template, [All-RP-PS]-DNA nonamer and Hoogsteen-paired (2'-OMe)-RNA strands containing the LNA units) led to the efficient inhibition of the process. Under the best conditions checked (four 5-Me-C-LNA units, three-fold excess over the RNA template) the inhibition was 94% effective, compared to 71% inhibition observed in the reference system with the Hoogsteen-paired (2'-OMe)-RNA strand carrying no LNA units. This kind of complexation may "arrest" harmful RNA oligomers (e.g., viral RNA or mRNA of unwanted proteins) and, beneficially, exclude them from enzymatic processes, otherwise leading to viral or genetic diseases.
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Affiliation(s)
- Anna Maciaszek
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry, Sienkiewicza 112, 90-363 Lodz, Poland.
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Guga P, Koziołkiewicz M. Phosphorothioate nucleotides and oligonucleotides - recent progress in synthesis and application. Chem Biodivers 2012; 8:1642-81. [PMID: 21922655 DOI: 10.1002/cbdv.201100130] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Piotr Guga
- Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Department of Bioorganic Chemistry, Sienkiewicza 112, PL-90-363 Łódź.
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Nawrot B, Rebowska B. DNA oligonucleotides containing stereodefined phosphorothioate linkages in selected positions. ACTA ACUST UNITED AC 2009; Chapter 4:Unit 4.34. [PMID: 19319859 DOI: 10.1002/0471142700.nc0434s36] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
This unit describes a method for the synthesis of DNA chimeric PO/PS-oligonucleotides with a stereodefined phosphorothioate bond in the selected position. Diastereomerically pure 5'-O-DMTr-N-protected-deoxyribonucleoside-3'-O-(2-thio-spiro-4,4-pentamethylene-1,3,2-oxathiaphospholane)s obtained according to the previously described protocol (UNIT 4.17) are transformed via a stereospecific 1,3,2-oxathiaphospholane-ring opening condensation into the corresponding dinucleoside phosphorothioates. Such dimers cannot be introduced into an oligonucleotide chain via the phosphoramidite approach since the unprotected P-S(-) bond is easily oxidized during routine I(2)/Py/water oxidation of the phosphite function. In the methodology described here, the reversible alkylation of the PS function is applied. Subsequently, the 3'-phosphoramidites of such PS-protected dimers prepared in situ are used for routine synthesis of chimeric PO/PS-oligonucleotides according to the phosphoramidite method. The presence of the alkylated PS-function requires modified conditions for oligonucleotide deprotection and cleavage from the solid support. Detailed procedures for the synthesis of PS-dimers and their incorporation into an oligonucleotide chain, as well as deprotection/purification steps are presented.
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Affiliation(s)
- Barbara Nawrot
- Department of Bioorganic Chemistry, Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Lodz, Poland
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1,3,2-Oxathiaphospholane approach to the synthesis of P-chiral stereodefined analogs of oligonucleotides and biologically relevant nucleoside polyphosphates. PURE APPL CHEM 2008. [DOI: 10.1351/pac200880081859] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Among the various classes of modified nucleotides and oligonucleotides, phosphorothioate analogs, in which the sugar-phosphate backbone is modified by the substitution of a sulfur atom for one of the nonbridging oxygen atoms, have been most extensively studied in both in vitro and in vivo experiments. However, this substitution induces P-chirality of the dinucleoside phosphorothioate moiety. Consequently, even short phosphorothioate oligonucleotides synthesized using standard chemical methods exist as mixtures of many diastereoisomers. In our laboratory, the oxathiaphospholane (OTP) method has been developed for a stereocontrolled synthesis of oligo(deoxyribonucleoside phosphorothioate)s. Recently, this approach has been extended to ribonucleoside derivatives, and stereodefined phosphorothioate diribonucleotides were incorporated into oligomers suitable for mechanistic studies on deoxyribozymes. Next, it was found that the OTP ring can be opened with nucleophiles as weak as the phosphate or pyrophosphate anion, giving rise to nucleoside α-thiopolyphosphates. Surprisingly, the reaction between nucleoside OTP and O,O-dialkyl H-phosphonate or O,O-dialkyl H-phosphonothioate led to nucleoside 5'-O-(α-thio-β-O,O-dialkyl-hypophosphate) or 5'-O-(α,β-dithio-β-O,O-dialkyl-hypophosphate), respectively, i.e., derivatives containing a direct P-P bond.
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Pallan PS, Lubini P, Bolli M, Egli M. Backbone-base inclination as a fundamental determinant of nucleic acid self- and cross-pairing. Nucleic Acids Res 2007; 35:6611-24. [PMID: 17905816 PMCID: PMC2095819 DOI: 10.1093/nar/gkm612] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The crystal structure of the duplex formed by oligo(2′,3′-dideoxy-β-d-glucopyranosyl)nucleotides (homo-DNA) revealed strongly inclined backbone and base-pair axes [Egli,M., Pallan,P.S., Pattanayek,R., Wilds,C.J., Lubini,P., Minasov,G., Dobler,M., Leumann,C.J. and Eschenmoser,A. (2006) Crystal structure of homo-DNA and nature's choice of pentose over hexose in the genetic system. J. Am. Chem. Soc., 128, 10847–10856]. This inclination is easily perceived because homo-DNA exhibits only a modest helical twist. Conversely, the tight coiling of strands conceals that the backbone-base inclinations for A- (DNA and RNA) and B-form (DNA) duplexes differ considerably. We have defined a parameter ηB that corresponds to the local inclination between sugar-phosphate backbone and base plane in nucleic acid strands. Here, we show its biological significance as a predictive measure for the relative strand polarities (antiparallel, aps, or parallel, ps) in duplexes of DNA, RNA and artificial nucleic acid pairing systems. The potential of formation of ps duplexes between complementary 16-mers with eight A and U(T) residues each was investigated with DNA, RNA, 2′-O-methylated RNA, homo-DNA and p-RNA, the ribopyranosyl isomer of RNA. The thermodynamic stabilities of the corresponding aps duplexes were also measured. As shown previously, DNA is capable of forming both ps and aps duplexes. However, all other tested systems are unable to form stable ps duplexes with reverse Watson–Crick (rWC) base pairs. This observation illustrates the handicap encountered by nucleic acid systems with inclinations ηB that differ significantly from 0° to form a ps rWC paired duplex. Accordingly, RNA with a backbone-base inclination of −30°, pairs strictly in an aps fashion. On the other hand, the more or less perpendicular orientation of backbone and bases in DNA allows it to adopt a ps rWC paired duplex. In addition to providing a rationalization of relative strand polarity with nucleic acids, the backbone-base inclination parameter is also a determinant of cross-pairing. Thus, systems with strongly deviating ηB angles will not pair with each other. Nucleic acid pairing systems with significant backbone-base inclinations can also be expected to display different stabilities depending on which terminus carries unpaired nucleotides. The negative inclination of RNA is consistent with the higher stability of duplexes with 3′- compared to those with 5′-dangling ends.
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Affiliation(s)
- Pradeep S. Pallan
- Department of Biochemistry, School of Medicine, Vanderbilt University, Nashville, TN 37232, USA, Alta Scuola Pedagogica, CH-6600 Locarno and Actelion Pharmaceuticals Ltd., CH-4123 Allschwil, Switzerland
| | - Paolo Lubini
- Department of Biochemistry, School of Medicine, Vanderbilt University, Nashville, TN 37232, USA, Alta Scuola Pedagogica, CH-6600 Locarno and Actelion Pharmaceuticals Ltd., CH-4123 Allschwil, Switzerland
| | - Martin Bolli
- Department of Biochemistry, School of Medicine, Vanderbilt University, Nashville, TN 37232, USA, Alta Scuola Pedagogica, CH-6600 Locarno and Actelion Pharmaceuticals Ltd., CH-4123 Allschwil, Switzerland
| | - Martin Egli
- Department of Biochemistry, School of Medicine, Vanderbilt University, Nashville, TN 37232, USA, Alta Scuola Pedagogica, CH-6600 Locarno and Actelion Pharmaceuticals Ltd., CH-4123 Allschwil, Switzerland
- *To whom correspondence should be addressed. +1 615 343 8070+1 615 322 7122
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