7,8-Dihydro-8-oxoadenine as a replacement for cytosine in the third strand of triple helices. Triplex formation without hypochromicity.
7,8-Dihydro-8-oxoadenine as a replacement for cytosine in the third strand of triple helices. Triplex formation without hypochromicity.
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7,8-二氢-8-氧代腺嘌呤作为三螺旋第三链中胞嘧啶的替代物。
DOI：
10.1021/bi00064a006
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发表时间：
1993
期刊：
影响因子：
2.9
通讯作者：
F. Hobbs
中科院分区：
文献类型：
--
作者：
M. Jetter;F. Hobbs
已知含有胸腺嘧啶和胞嘧啶（或 5-甲基胞嘧啶）碱基的寡核苷酸通过 T.AT 和 C+.GC 碱基三联体与双链 DNA 中的特定高嘌呤序列结合。这种三螺旋第三链中的胞嘧啶可以完全被7,8-二氢-8-氧代腺嘌呤碱基取代，该碱基不需要质子化来形成碱基三联体。使用天然 PAGE 和抑制三链体定向光交联的实验表明，第三链中含有 7,8-二氢-8-氧代腺嘌呤的三链体在 pH 6.0 下与含有 5-甲基胞嘧啶的三链体一样稳定。与 5-甲基胞嘧啶的三链体不同，7,8-二氢-8-氧代腺嘌呤三链体的稳定性在 pH 值升至 7.4 时并没有显着降低。令人惊讶的是，仅含有胸腺嘧啶和7,8-二氢-8-氧代腺嘌呤的寡核苷酸形成的三链体与显着的减色性无关，并且在常规热变性实验中无法检测到。
Oligonucleotides containing thymine and cytosine (or 5-methylcytosine) bases are known to bind to specific homopurine sequences in double-stranded DNA by means of T.AT and C+.GC base triplets. Cytosine in the third strand of such triple helices can be completely replaced by 7,8-dihydro-8-oxoadenine a base which should not require protonation to form base triplets. Experiments using native PAGE and inhibition of triplex-directed photo-cross-linking demonstrate that triplexes with 7,8-dihydro-8-oxoadenine in the third strand are as stable at pH 6.0 as triplexes with 5-methylcytosine. The stability of triplexes with 7,8-dihydro-8-oxoadenine, unlike those with 5-methylcytosine, is not substantially diminished upon raising the pH to 7.4. Surprisingly, triplex formation with an oligonucleotide containing only thymine and 7,8-dihydro-8-oxoadenine was not associated with significant hypochromicity and could not be detected in conventional thermal denaturation experiments.