PubMed Health⌕ Search

Biomedical subjects

Kazuhiko Nakatani

Publications and source records attributed to Kazuhiko Nakatani.

At least 19 recordsLinked to original sources
PubMed2006

Evaluation of mismatch-binding ligands as inhibitors for Rev-RRE interaction.

Drugs targeting the stem-loop IIB of Rev responsible element (RRE) of HIV-1 mRNA are potential therapeutic agents for HIV-1 infection. The stem loop is characterized by an internal loop consist of consecutive G-G and G-A mismatches, which is the single binding site for Rev protein for nuclear export of viral mRNA. We report here that ligands binding to G-G and G-A mismatches in duplex DNA also bind to the internal loop in competition with Rev peptide and lead to the dissociation of pre-formed Rev-RRE complex in a model system.

Base Pair Mismatch↗
PubMed2006

Control of DNA hybridization by photoswitchable mismatch binding ligands.

We herein demonstrate that mismatch binding ligands (MBL) can function as a molecular glue which brings two single stranded DNA (ssDNA) together to form the double stranded DNA (dsDNA). Incorporation of a photoisomerizable azobenzene linkage provides further ability of reversibly controlling duplex stability with light.

Azo Compounds↗
PubMed2006

Inhibition of DNA replication by a d(CAG) repeat binding ligand.

Trinucleotide repeat expansions in genomic DNA are the molecular basis of a number of genetic diseases. The (CAG)n, (CTG)n, and (CGG)n repeats share the common sequence CXG, and inherently produce a hairpin structure involving X-X mismatch base pairs flanked by two G-C base pairs. The chance of a strand slippage leading to the repeat expansion is considered to increase with increasing stability of the hairpin form. Here we show our synthetic ligand naphthyridine-azaquinolone (NA) stabilized a hairpin form of the (CAG)n repeat and inhibited the polymerase-mediated DNA synthesis.

Adenine↗
PubMed2006

Measurement of circular dichroism and structural chemical research of d(CG)6 and d(TA)6.

It was known that d(CG)(6) became left-handed Z-DNA by a theoretical calculation. We carried out a CD measurement of d(CG)(6) at room temperature. B-Z transition was occurred when I raised the concentration of Mg salt. In addition, I confirmed that the Mg salt concentration caused B-Z transition by the lower concentration under the existence of cobalt hexamine. Structure of d(TA)(6) is not known. We performed the CD measurement of d(TA)(6) at low temperature. Structure changed from B type when I raised the Mg salt concentration in an existence of cobalt hexamine. I am examining structure now.

Circular Dichroism↗
PubMed2005

Small-molecule ligand induces nucleotide flipping in (CAG)n trinucleotide repeats.

DNA trinucleotide repeats, particularly CXG, are common within the human genome. However, expansion of trinucleotide repeats is associated with a number of disorders, including Huntington disease, spinobulbar muscular atrophy and spinocerebellar ataxia. In these cases, the repeat length is known to correlate with decreased age of onset and disease severity. Repeat expansion of (CAG)n, (CTG)n and (CGG)n trinucleotides may be related to the increased stability of alternative DNA hairpin structures consisting of CXG-CXG triads with X-X mismatches. Small-molecule ligands that selectively bound to CAG repeats could provide an important probe for determining repeat length and an important tool for investigating the in vivo repeat extension mechanism. Here we report that napthyridine-azaquinolone (NA, 1) is a ligand for CAG repeats and can be used as a diagnostic tool for determining repeat length. We show by NMR spectroscopy that binding of NA to CAG repeats induces the extrusion of a cytidine nucleotide from the DNA helix.

DNA↗
PubMed2005

A new ligand binding to G-G mismatch having improved thermal and alkaline stability.

Naphthyridine dimer (ND) specially binds to guanine-guanine (G-G) mismatch in duplex DNA. In order to improve the thermal and alkaline stability and binding ability of the ligand, we have examined structural modification of the linker. A new ligand (NNC) possessing 2-amino-1,8-naphthyridines and a carbamate linker is much more thermally stable than ND. The half-life of NNC is 2.5 times longer than that of ND at 80 degrees C. NNC is also much more stable than ND under alkaline conditions. In addition, NNC binds to G-G mismatch more strongly than ND. The improved stability and the binding of NNC to the G-G mismatch would be suitable for the practical use of NNC-immobilized sensor.

Base Pair Mismatch↗
PubMed2005

NMR structural analysis of the G.G mismatch DNA complexed with naphthyridine-dimer.

Naphthyridine-dimer (ND) specifically recognizes G.G mismatch DNA (Figure 1). However, its detailed recognition mechanism is not clear. Here a DNA oligomer d(CTAACGGAATG)/d(CATTCGGTTAA) complexed with ND was studied by NMR. The stoichiometry of DNA to ND was determined to be 1:2 at NMR concentration (2.5 mM). Proton resonances were completely assigned including H5' and H5'' using 1H-1H and 1H-13C 2D spectra of the complex. These spectra showed that four naphthyridine rings are staked in the helix and form hydrogen bonds with the four G residues in CGG/CGG region. These results indicate ND can specifically recognize the CGG/CGG sequence.

Base Pair Mismatch↗
PubMed2005

Application of L-DNA as a molecular tag.

Enantiomeric DNA termed as L-DNA has unique properties. One is the ability of hybridizing to the complementary DNA as natural D-DNA. Another property is that the L-DNA could be recognized much more weakly by enzymes than D-DNA. We have focused our attention on these properties and applied L-DNA as a molecular tag. Here, we report that L-D chimera DNA is useful for PCR primers and subsequent separation and hybridization. Precise investigation revealed that in the process of PCR, L-DNA region could not be the PCR template and the polymerase extension reaction stopped at the boundary between L- and D-DNA region. As a result, L-DNA region formed like a "sticky end" and played a role of molecular tag. According to the L-DNA tag sequence, the produced L-DNA-tagged PCR products were easily separated or hybridized on the solid surface where the complementary L-DNA was pre-immobilized.

DNA↗
PubMed2005

Molecular labeling of the CGG trinucleotide repeat.

The new molecular ligand naphthyridine carbamate dimer (NC), possessing 2-amino-1,8-naphthyridines and a carbamate linker, specially binds to guanine-guanine (G-G) mismatch in duplex DNA. The results of T(m) measurements showed that NC selectively bound to CGG/CGG triad with high deltaT(m) of 23.1 degrees C. The exclusive stoichiometry 2:1 of the complex of NC with CGG/CGG triad, obtained by the measurements of cold spray ionization time-of-flight mass spectrometry (CSI-TOF MS), showed that NC bound to CGG/CGG triad strongly with two molecules.

Base Pair Mismatch↗
PubMed2005

Solution structure of a small-molecular ligand complexed with CAG trinucleotide repeat DNA.

NMR structure of the first identified ligand, naphthyridine-azaquinolone (NA), complexed with the CAG-CAG triad is reported. The determined structure revealed the invasive ligands binding to the A-A mismatch and flanking G-C base pairs, causing the widowed cytosines to flip out from pi-stack. Hydrogen-bond pairs between NA and DNA, naphthyridine-guanine and azaquinolone-adenine, are well stacked in the right-handed DNA helix, showing structural mimicry of Watson-Crick base pairing. This is the first observation that the small molecular ligand induced the base flipping of the nucleotide base in the Watson-Crick base pair.

Base Pairing↗
PubMed2004

2-Ureidoquinoline: a useful molecular element for stabilizing single cytosine and thymine bulges.

We have demonstrated that aromatic heterocycles having hydrogen-bonding surfaces complementary to those of nucleotide bases are effective molecular elements for the binding to single nucleotide bulges and base mismatches. We here report that a new molecule, 2-ureidoquinoline having an alignment of hydrogen-bonding groups in the order of acceptor-donor-donor stabilizes single cytosine and thymine bulges in duplex DNAs. Furthermore, a dimeric form of 2-ureidoquinoline stabilizes cytosine-cytosine and cytosine-thymine mismatches.

Base Pair Mismatch↗
PubMed2004

The binding of guanine-guanine mismatched DNA to naphthyridine dimer immobilized sensor surfaces: kinetic aspects.

Naphthyridine dimer composed of two naphthyridine chromophores and a linker connecting them strongly, and selectively, binds to the guanine-guanine mismatch in duplex DNA. The kinetics for the binding of the G-G mismatch to the naphthyridine dimer was investigated by surface plasmon resonance assay. The sensor surface was prepared by immobilizing naphthyridine dimer through a long poly(ethylene oxide) linker with the ligand density of 9.1 x 10(-12) fmolnm(-2). The kinetic analyses revealed that the binding of the G-G mismatch was sequence dependent on the flanking base pairs, and the G-G mismatches flanking at least one G-C base pair bound to the surface via a two-step process with a 1:1 DNA-ligand stoichiometry. The first association rate constant for the binding of the G-G mismatch in the 5'-CGG-3'/3'-GGC-5' sequence to the naphthyridine dimer-immobilized sensor surface was 3.2 x 10(3)M(-1)s(-1) and the first dissociation rate constant was 1.4 x 10(-2)s(-1). The association and dissociation rate constants for the second step were insensitive to the flanking sequences, and were almost of the same order of magnitude as the first dissociation rate constant. This indicates that the second step had only a small energetic contribution to the binding. The association constant calculated from kinetic parameters was 2.7 x 10(5)M(-1), which is significantly smaller than the apparent association constants obtained from experiments in solution. Electrospray ionization time-of-flight (ESI-TOF) mass spectrometry on the complex produced from the G-G mismatch and naphthyridine dimer showed the formation of the 1:1 complex and a 1:2 DNA-ligand complex in solution. The latter complex became the dominant complex when a six-fold excess of naphthyridine dimer was added to DNA.

Base Pair Mismatch↗
PubMed2004

Highly sensitive detection of GG mismatched DNA by surfaces immobilized naphthyridine dimer through poly(ethylene oxide) linkers.

Naphthyridine dimer is a unique molecule that strongly, and selectively, binds to the guanine-guanine mismatch in duplex DNA. We have synthesized naphthyridine dimers possessing a different length of poly(ethylene oxide) (PEO) linker, and immobilized them to CM5 sensor chip to carry out a surface plasmon resonance (SPR) assay of DNA duplexes containing a single base mismatch. The sensitivity of the sensor remarkably increased with increasing numbers of PEO units incorporated into the linker. With the sensor surface immobilized naphthyridine dimer for 1.5 x 10(3) response unit (RU) through three PEO units, the distinct SPR signal was observed at a concentration of 1 nM of the 27-mer G-G mismatch.

Base Pair Mismatch↗