Biomedical subjects

Kenichi Miyata

Publications and source records attributed to Kenichi Miyata.

8 recordsLinked to original sources

PubMed2026

Plasticity of extrachromosomal DNA segregation during drug adaptation.

Uneven segregation during mitosis is a striking feature of extrachromosomal DNA (ecDNA). Because ecDNA lacks a centromere, it is thought to segregate stochastically, generating intratumoral heterogeneity in genomic copy number. Drug treatment can readily change ecDNA copy number, enabling cells to acquire drug resistance, yet whether these changes reflect static selection of pre-existing clones or active reconfiguration under stress remains unresolved. To address this, we develop a high-throughput framework combining single-cell DNA sequencing with cellular barcoding for clonal tracking. Single-cell cloning reveals that not all clones exhibit identical segregation modes even under drug-free conditions. Under treatment, resistant populations do not simply arise from pre-existing clones with favorable ecDNA states; instead, some clones actively reconfigure their segregation behavior to generate resistant cells. Thus, although ecDNA generally segregates stochastically, it can undergo nonrandom, actively regulated segregation under drug stress, raising the possibility of therapeutically targeting ecDNA segregation mechanisms to counteract adaptive resistance.

Extrachromosomal DNA↗

PubMed2007

Synthesis and fluorescent properties of bi- and tricyclic 4-N-carbamoyldeoxycytidine derivatives.

New bi- and tricyclic deoxycytidine derivatives (dChpd, dCmpp, dCtpp, dCppp) were synthesized as analogues of a fluorescent nucleoside, dChpp, previously reported. The carbamoyl group of dChpd and the 5-position of the cytosine ring are bridged via an ethylene linker so that the modified group forms a nonplanar structure with the cytosine ring. The fluorescent study of dChpd indicated that the coplanar structure between the carbamoyl group and the cytosine ring is of importance. N-Methylation of the carbamoyl group (dCmpp) weakened the intensity of the fluorescence of dChpp, and the derivative (dCtpp), which had a thiocarbamoyl group, lost its fluorescent property. Moreover, addition of a pyrrolo-ring (dCppp) to dChpp enhanced the intensity of fluorescence, and an emission light was observed with a marked Stokes shift of 120 nm.

Deoxycytidine↗

PubMed2006

Synthesis and properties of a new fluorescent bicyclic 4-N-carbamoyldeoxycytidine derivative.

[reaction: see text] A bicyclic 4-N-carbamoyldeoxycytidine derivative (1, dC(hpp)) geometrically locked was synthesized as a new fluorescent nucleobase. The hybridization properties of oligodeoxynucleotides containing dC(hpp) were investigated by use of T(m) analysis. It was found that dC(hpp) forms stable base pairs not only with the complementary guanine base, but also with the adenine base. Interestingly, the fluorescence of dC(hpp) was suppressed only when a dC(hpp)-dG base pair was formed.

Base Pairing↗

PubMed2006

Synthesis of fluorescent cyclic cytosine nucleosides and their fluorescent properties upon incorporation into oligonucleotides.

We report here the synthesis and spectroscopic characterization of a new fluorescent pyrimidopyrimidoindole nucleoside derivative (dC(PPI)) modified at the cytosine base. The photophysical properties of dC(PPI) were examined by fluorescent spectroscopy and quantum chemical calculations. It was found that dC(PPI)-labeled oligonucleotides gave almost the same thermal stability as that of the corresponding unmodified sequences. In addition, the quantum yield of dC(PPI) in the double-stranded state was significantly higher than that in the single-stranded state.

DNA Probes↗

PubMed2004

Synthesis and properties of 5-pyrrolyl-cytidine and uridine derivatives.

New 5-modified pyrimidine derivatives that were expected to form Hoogsteen-type triplexes have been synthesized, 5-pyrrolyl-2'-O-methylcytosine was designed as a protonated cytosine mimic to realize pH-independent triplex formation with the complementary G-C Watson-Crick base pair by inducing the imino tautomer of cytosine. 5-Pyrrolyl-2'-O-methyluridine was also synthesized to enhance the stacking effect for stabilization of triplexes. For the deprotection of the DMTr group in the phosphoramidite method, EtSi3H was added as the scavenger of the dimethoxytrityl-cation to avoid side-reactions on the pyrrolyl group. The triplex forming ability of TFOs containing modified nucleosides was evaluated by Tm experiments under various conditions.

Cytidine↗

PubMed2003

HSV-1 amplicon peptide display vector.

There are significant uses for expressing foreign peptide epitopes in viral surface attachment proteins in terms of investigating viral targeting, biology, and immunology. HSV-1 attachment, followed by fusion and entry, is mediated in large part by the binding of viral surface glycoproteins to cell surface receptors, primarily through heparan sulfate (HS) glycosaminoglycan residues. We constructed a HSV-1 amplicon plasmid (pCONGA) carrying the gC primary attachment protein gene with unique restriction sites flanking the HS binding domain (HSBD) (residues 33-176) to allow rapid, high efficiency substitution with foreign peptide domains. To test this system, a His tag with an additional unique restriction site (for selection and assay digests) was recombined into the pCONGA HSBD site to create pCONGAH. Infection of pCONGAH transfected Vero cells with HSV-1 helper virus (gCdelta2-3 or hrR3) produced His-modified gC as demonstrated by western blot analysis with co-localization of anti-gC and anti-His tag antibodies to a protein of appropriate molecular weight (50 kd). As CONGA and CONGAH amplicons carry a GFP transgene and the gCdelta2-3 and hrR3 viruses carry a lacZ transgene, vector stocks produced from 1 x 10(5) Vero cells could be titered for competent vector on cell monolayers and were demonstrated to contain 2 x 10(5) amplicon vector transducing units (t.u.)/ml and 1 x 10(7) virus t.u./ml. As the amplicon plasmids also contain the neomycin resistance gene (neo(r)), long term vector producer cell lines were created using G418 selection. This amplicon system provides means to rapidly and efficiently generate HSV-1 amplicon and viral vector expressing surface attachment proteins modified with different peptide epitopes for investigational and therapeutic uses, with the advantages of an amplicon plasmid that can be used with interchangeable helper virus vectors, is designed specifically for easy manipulation, and carries GFP and neo(r) transgenes for marker and selection functions.

Animals↗

PubMed2002

A new method for the synthesis of oligodeoxyribonucleotides containing 4-N-alkoxycarbonyldeoxycytidine derivatives and their hybridization properties.

Oligodeoxyribonucleotides incorporating 4-N-alkoxycarbonyldeoxycytidine derivatives were synthesized on polystyrene-type ArgoPore resins having a new benzyloxy(diisopropyl)silyl linker, by use of ZnBr(2) as the detritylating agent. The first 3'-terminal thymidine could be attached to the resin by successive in situ reactions of 5'-O-DMTr-thymidine with diisopropylsilanediyl ditriflate and an ArgoPore resin containing hydroxyl groups. The use of this new silanediyl-type linker allowed release of the DNA chain from the resin by treatment with TBAF under neutral conditions. The T(m) experiments apparently showed that incorporation of 4-N-alkoxycarbonyldeoxycytidines into DNA strands resulted in higher hybridization affinity with the complementary DNA strands than that of 4-N-acyldeoxycytidines. In addition, comparable T(m) studies using oligodeoxyribonucleotides incorporating acyl (RC(O)-) groups and alkoxyacyl (RO(CH(2))(n)C(O)-) groups having the same chain length show that the latter tend to exhibit higher T(m) values than the former. It turned out that 4-N-alkoxycarbonyldeoxycytidines can form base pairs not only with deoxyguanosine but also with deoxyadenosine. Based on the ab initio calculations of the hydrogen bond energies of the possible base pairs formed between 4-N-methoxycarbonyl-1-methylcytosine and 9-methyladenine and the NMR analysis of the base-pairs of (15)N-labeled 4-N-alkoxycarbonyldeoxycytidines with deoxyadenosine derivatives, we conclude that the base pair involves two unique hydrogen bonds between the cytosyl 4-NH group and the adenyl N(1) atom and between the O atom of the ester group and the adenyl 6-NH group.

Adenosine↗

PubMed2002

Hybridization ability and base pair geometry of modified deoxycytidine derivatives having a 4-N-carbamoyl group.

Modified oligodeoxyribonucleotides incorporating 4-N-carbamoyldeoxycytidine derivatives were synthesized. The 1H-NMR of 4-N-carbamoyldeoxycytidine suggests that the carbamoyl group forms an intramolecular hydrogen bond with the cytosine ring nitrogen atom and this geometry would inhibit formation of the Watson-Crick base pair with a guanine base. However, the Tm analysis of the modified oligodeoxynucleotides revealed that, in the process of their hybridization with the complementary oligodeoxynucleotides, the orientation of the carbamoyl group changed in a manner where the stable Watson-Crick base pair can be formed with the guanine base.

Base Pairing↗