Development of antiparallel-type triplex-forming oligonucleotides containing quinoline derivatives capable of recognizing a T-A base pair in a DNA duplex.

A triplex-forming oligonucleotide (TFO) can bind to genomic DNA and inhibit the expression of genes with specific sequences. However, to date, there have been a few reports of modified bases in antiparallel TFOs that can recognize and strongly bind to T-A base pairs. In this study, we introduced several quinoline derivatives into antiparallel TFOs to develop modified bases that can recognize the T-A base pair and evaluated their ability to form triplexes and to discriminate between base pairs.

Chemical synthesis and biochemical characterization of cyclic oligonucleotides containing acyl groups at both 5'- and 3'-terminal positions.

Modified oligonucleotides, whose ON-OFF switch of hybridization can be controlled by an external stimulus, are important to understanding life phenomena and efficient treatment of diseases. The ON-OFF switch can be completely controlled by chemical modification of the oligonucleotide such as cyclization. However, their chemical modifications of the previous cyclic oligonucleotides remain after the addition of an external stimulus.

Chemical synthesis and properties of modified oligonucleotides containing 5'-amino-5'-deoxy-5'-hydroxymethylthymidine residues.

In this study, we designed 5'-amino-5'-deoxy-5'-hydroxymethylthymidine as a new oligonucleotide modification with an amino group directly attached to the 5'-carbon atom. We successfully synthesized two isomers of 5'-amino-5'-deoxy-5'-hydroxymethylthymidine via dihydroxylation of the 5'-vinyl group incorporated into 5'-deoxy-5'-C-methenylthymidine derivative. Moreover, it was found that the nuclease resistance, binding selectivity to single-stranded RNA, and triplex-forming ability of an oligonucleotide containing T residues of the new compound were higher than those of the unmodified oligonucleotide.

The ability of a triplex-forming oligonucleotide to recognize T-A and C-G base pairs in a DNA duplex is enhanced by incorporating N-acetyl-2,7-diaminoquinoline.

A triplex-forming oligonucleotide (TFO) can recognize the homopurine-homopyrimidine sequence in DNA duplexes and inhibit the transcription of targeted mRNAs. Recently, we reported that N-acetyl-2,7-diamino-1,8-naphthyridine (N), incorporated into a TFO, has high binding ability and base recognition selectivity for the pyrimidine bases in the purine-rich chain of the DNA duplex at pH 7.4.

Synthesis of and triplex formation in oligonucleotides containing 2'-deoxy-6-thioxanthosine.

This study aimed to synthesize triplex-forming oligonucleotides (TFOs) containing 2'-deoxy-6-thioxanthosine (sX) and 2'-deoxy-6-thioguanosine (sGs) residues and examined their triplex-forming ability. Consecutive arrangement of sX and sGs residues increased the triplex-forming ability of the oligonucleotides more than 50 times, compared with the unmodified TFOs. Moreover, the stability of triplex containing a mismatched pair was much lower than that of the full-matched triplex, though sX could form a sX-GC mismatched pair via tautomerization of sX.

pH-Dependent Switching of Base Pairs Using Artificial Nucleobases with Carboxyl Groups.

In this study, we report the synthesis of modified oligonucleotides consisting of benzoic acid or isophthalic acid residues as new nucleobases. As evaluated by UV thermal denaturation analysis at different pH conditions (5.0, 6.