Transcription and reverse transcription of artificial nucleic acids involving backbone modification by template-directed DNA polymerase reactions.

Oligodeoxyribonucleotides (ODN) where the phosphodiester linkage had been replaced with an amide-type linker [-CH(2)C=ONH-] or an amine-type linker [-CH(2)CH(2)NH-] were synthesized to investigate the effect of these backbone modifications on polymerase reactions. In addition, a triphosphate analogue of thymidine dinucleotide with the amide-type linker was synthesized and enzymatic insertion of the amide linkage into ODN was attempted using this analogue for the polymerase reaction. Primer extension reactions using three types of thermostable DNA polymerases, KOD(exo-), Vent(exo-) and Taq were performed for the assays.

Smart conferring of nuclease resistance to DNA by 3'-end protection using 2',4'-bridged nucleoside-5'-triphosphates.

Incorporation of 2',4'-bridged nucleotides into the 3'-end of oligodeoxyribonucleotide (ODN) was examined using terminal deoxynucleotidyl transferase (TdT). The three types of 2',4'-bridged nucleoside-5'-triphospates with different bridging structures used were incorporated efficiently into the 3'-end of DNA by TdT, although only single nucleotide incorporation was observed. Nuclease resistance was conferred on DNA, depending on the types of bridging nucleotides added.

Effect of backbone-modification of oligodeoxyribonucleic acid on primer extension reactions.

We synthesized two types of modified DNA templates in which the phosphodiester linkage was replaced with an amide-type linker [-CH(2)C=ONH-] or an amine-type linker [-CH(2)CH(2)NH-]. Primer extension reactions were performed using these modified DNA templates to investigate the effect of backbone modification on polymerase reactions. Our results indicated that the polymerase reaction was affected much more by the insertion of the cationic flexible amine-type linker than by insertion of the neutral rigid amide-type linker.

Systematic analysis of enzymatic DNA polymerization using oligo-DNA templates and triphosphate analogs involving 2',4'-bridged nucleosides.

In order to systematically analyze the effects of nucleoside modification of sugar moieties in DNA polymerase reactions, we synthesized 16 modified templates containing 2',4'-bridged nucleotides and three types of 2',4'-bridged nucleoside-5'-triphospates with different bridging structures. Among the five types of thermostable DNA polymerases used, Taq, Phusion HF, Vent(exo-), KOD Dash and KOD(exo-), the KOD Dash and KOD(exo-) DNA polymerases could smoothly read through the modified templates containing 2'-O,4'-C-methylene-linked nucleotides at intervals of a few nucleotides, even at standard enzyme concentrations for 5 min. Although the Vent(exo-) DNA polymerase also read through these modified templates, kinetic study indicates that the KOD(exo-) DNA polymerase was found to be far superior to the Vent(exo-) DNA polymerase in accurate incorporation of nucleotides.

Arginine-modified DNA aptamers that show enantioselective recognition of the dicarboxylic acid moiety of glutamic acid.

We have screened glutamic acid-binding aptamers from a modified DNA pool containing arginine residues using the method of systematic evolution of ligands by exponential enrichment (SELEX). Thirty-one modified DNA molecules were obtained from the enriched pool after the 17th round of selection, and their binding affinities for the target were evaluated by binding assays using affinity gels. Three modified DNA molecules having higher affinity were sequenced and we determined their affinity and specificity for the target by surface plasmon resonance (SPR) measurements.

Polymerisation of a DNA strand using oligo-DNA template with modified bases, sugars and phosphates.

We have attempted to synthesise a complimentary strand using oligo-DNA with modified bases, sugars and phosphates as a template strand by polymerase reaction. Analogues bearing C5-substituted uracil, those with amide linkage [-CH2C=ONH-] in place of phospho-diester linkage and those bearing 2'-O, 4'-C-bridged sugar were used. Primer extension reactions were carried out to synthesise complimentary DNA strands.

Substrate property and incorporation accuracy of various dATP analogs during enzymatic polymerization using thermostable DNA polymerases.

DNA aptamers and DNAzymes with similar function to antibodies and enzymes can be produced by in vitro selection. They would be useful as research tools for molecular biology and as indicators of specific substances for the analysis of clinical and food samples. Furthermore, development of modified DNA molecules aimed to diversify function and improve activity has recently proceeded by introducing functionalities to these DNA molecules.

Systematic characterization of 2'-deoxynucleoside- 5'-triphosphate analogs as substrates for DNA polymerases by polymerase chain reaction and kinetic studies on enzymatic production of modified DNA.

We synthesized C5-modified analogs of 2'-deoxyuridine triphosphate and 2'-deoxycytidine triphosphate and investigated them as substrates for PCRs using Taq, Tth, Vent(exo-), KOD Dash and KOD(exo-) polymerases and pUC 18 plasmid DNA as a template. These assays were performed on two different amplifying regions of pUC18 with different T/C contents that are expected to have relatively high barriers for incorporation of either modified dU or dC. On the basis of 260 different assays (26 modified triphosphates x 5 DNA polymerases x 2 amplifying regions), it appears that generation of the full-length PCR product depends not only on the chemical structures of the substitution and the nature of the polymerase but also on whether the substitution is on dU or dC.