Sanghvi Y S, Hoke G D, Freier S M, Zounes M C, Gonzalez C, Cummins L, Sasmor H, Cook P D
ISIS Pharmaceuticals, Carlsbad, CA 92008.
Nucleic Acids Res. 1993 Jul 11;21(14):3197-203. doi: 10.1093/nar/21.14.3197.
6-Azathymidine, 6-aza-2'-deoxycytidine, 6-methyl-2'-deoxyuridine, and 5,6-dimethyl-2'-deoxyuridine nucleosides have been converted to phosphoramidite synthons and incorporated into oligodeoxynucleotides (ODNs). ODNs containing from 1 to 5 of these modified pyrimidines were compared with known 2'-deoxyuridine, 5-iodo-2'-deoxyuridine, 5-bromo-2'-deoxyuridine, 5-fluoro-2'-deoxyuridine, 5-bromo-2'-deoxycytidine, and 5-methyl-2'-deoxycytidine nucleoside modifications. Stability in 10% heat inactivated fetal calf serum, binding affinities to RNA and DNA complements, and ability to support RNase H degradation of targeted RNA in DNA-RNA heteroduplexes were measured to determine structure-activity relationships. 6-Azathymidine capped ODNs show an enhanced stability in serum (7- to 12-fold increase over unmodified ODN) while maintaining hybridization properties similar to the unmodified ODNs. A 22-mer ODN having its eight thymine bases replaced by eight 6-azathymines or 5-bromouracils hybridized to a target RNA and did not inhibit RNase H mediated degradation.
6-氮胸苷、6-氮杂-2'-脱氧胞苷、6-甲基-2'-脱氧尿苷和5,6-二甲基-2'-脱氧尿苷核苷已被转化为亚磷酰胺合成子，并掺入到寡脱氧核苷酸（ODN）中。将含有1至5个这些修饰嘧啶的ODN与已知的2'-脱氧尿苷、5-碘-2'-脱氧尿苷、5-溴-2'-脱氧尿苷、5-氟-2'-脱氧尿苷、5-溴-2'-脱氧胞苷和5-甲基-2'-脱氧胞苷核苷修饰进行比较。测定了它们在10%热灭活胎牛血清中的稳定性、与RNA和DNA互补物的结合亲和力以及在DNA-RNA异源双链体中支持靶向RNA的核糖核酸酶H降解的能力，以确定构效关系。6-氮胸苷封端的ODN在血清中显示出增强的稳定性（比未修饰的ODN增加7至12倍），同时保持与未修饰的ODN相似的杂交特性。一个22聚体的ODN，其八个胸腺嘧啶碱基被八个6-氮胸苷或5-溴尿嘧啶取代，与靶RNA杂交，并且不抑制核糖核酸酶H介导的降解。
