- Post-synthetic introduction of labile functionalities onto purine residues via 6-methylthiopurines in oligodeoxyribonucleotides
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Two methods are described for the preparation of oligodeoxynucleotides containing 6-methylthiopurine residues. 6-Methylthiopurine phosphoramidite (6) has been prepared and incorporated into oligomers. Methylation with methyl iodide of 6-thiopurine (or 6-thioguanine) in oligomers also exclusively produces oligomers containing 6-methylthiopurine (or 6-methylthioguanine). The methylthio group at defined purine residues in the deprotected oligomers can be oxidized selectively and converted at the final step into various functional groups including radioactive 35S-thio group, a useful tag for cross-linking studies.
- Xu, Yao-Zhong
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p. 10737 - 10750
(2007/10/03)
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- Methylation of mercaptopurine, thioguanine, and their nucleotide metabolites by heterologously expressed human thiopurine S-methyltransferase
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Thiopurine S-methyltransferase (TPMT), a cytosolic enzyme that exhibits genetic polymorphism, catalyzes S-methylation of mercaptopurine (MP) and thioguanine (TG), yielding S-methylated nucleobases that are inactive, whereas S-methylated nucleotides of these thiopurines are cytotoxic. A yeast- based heterologous expression system was therefore used to characterize human TPMT-catalyzed methylation of MP, TG, and their principal nucleotide metabolites [thioinosine monophosphate (TIMP) and thioguanosine monophosphate (TGMP), respectively]. MP, TG, TIMP, and TGMP were all substrates for human TPMT, exhibiting similar Michaelis-Menten kinetic parameters (K(m), 10.6- 27.1 μM; V(max), 31-59 nmol/min/mg of TPMT). Consistent with these kinetic parameters, human leukemia cells (CEM) incubated for 24 hr with 10 μM MP or TG accumulated significantly higher (2.3-fold, p = 0.01) concentrations of methyl-TIMP after MP incubation than methyl-TGMP after TG incubation, due to the 2.7-fold higher concentration of TIMP after MP incubation, compared with TG nucleotides (TGN) after TG incubation. Moreover, intracellular accumulation of TGN was 2.5-fold greater after TG incubation than after MP incubation (p = 0.01). These data establish that MP, TG, and their principal nucleotide metabolites are comparable substrates for polymorphic TPMT, and they demonstrate significant differences in the accumulation of active TGN and methylated nucleotides when leukemia cells are treated with MP versus TG.
- Krynetski, Eugene Y.,Krynetskaia, Natalia F.,Yanishevski, Yuri,Evans, William E.
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p. 1141 - 1147
(2007/10/03)
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- Preparation of oligodeoxynucleotides containing 6-methylthiopurine residues by chemical synthesis or specific methylation
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Two methods (chemical synthesis and specific methylation) are described for the preparation of oligodeoxynucleotides containing 6-methylthiopurine residues. 6-Methylthiopurine phosphoramidite (6) is prepared and incorporated into oligomers. Methylation with methyl iodide of 6-thiopurine (or 6-thioguanine) in oligonucleotides also leads to exclusive production of 6-methylthiopurine (or 6-methylthioguanine) oligomers.
- Xu,Zheng,Swann
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p. 929 - 933
(2007/10/02)
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- SYNTHESIS OF 2-DEOXY-β-D-RIBONUCLEOSIDES AND2,3-DIDEOXY.β-D-PENTOFURANOSIDES ON IMMOBILIZED BACTERIAL CELLS
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Alginate gel-entrapped cells of auxotrophic thymine-dependent strain of E. coli catalyze the transfer of 2-deoxy-D-ribofuranosyl moiety of 2'-deoxyuridine to purine and pyrimidine bases as well as their aza and deaza analogs.All experiments invariably gave β-anomers; in most cases, the reaction was regiospecific, affording N9-isomers in the purine and N1-isomers in the pyrimidine series.Also a 2,3-dideoxynucleoside can serve as donor of the glycosyl moiety.The acceptor activity of purine bases depends only little on substitution, the only condition being the presence of N7-nitrogen atom.On the other hand, in the pyrimidine series the activity is limited to only a narrow choice of mostly short 5-alkyl and 5-halogeno uracil derivatives.Heterocyclic bases containing amino groups are deaminated; this can be avoided by conversion of the base to the corresponding N-dimethylaminomethylene derivative which is then ammonolyzed.The method was verified by isolation of 9-(2-deoxy-β-D-ribofuranosyl) derivatives of adenine, guanine, 2-chloroadenine, 6-methylpurine, 8-azaadenine, 8-azaguanine, 1-deazaadenine, 3-deazaadenine, 1-(2-deoxy-β-D-ribofuranosyl) derivatives of 5-ethyluracil, 5-fluorouracil, and 9-(2,3-deoxy-β-D-pentofuranosyl)hypoxanthine, 9-(2,3-deoxy-β-D-pentofuranosyl)-6-methylpurine, and other nucleosides.
- Votruba, Ivan,Holy, Antonin,Dvorakova, Hana,Guenter, Jaroslav,Hockova, Dana,et al.
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p. 2303 - 2330
(2007/10/02)
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- SYNTHESIS AND CROSSLINKING PROPERTIES OF A DEOXYOLIGONUCLEOTIDE CONTAINING N6,N6-ETHANODEOXYADENOSINE
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We report the synthesis of 5' HO-dT6(N6,N6-ethanodeoxyadenosine)T14.This oligonucleotide specifically crosslinks with 5' HO-dA14CA6T at pH 7.5 and 20 deg C with a half-life of approximately one day.
- Matteucchi, M. D.,Webb, T. R.
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p. 2469 - 2472
(2007/10/02)
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