Department of Chemistry and Center for Protein and Nucleic Acid Research, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
J Am Chem Soc. 2009 Oct 21;131(41):14620-1. doi: 10.1021/ja906186f.
Expansion of the genetic alphabet with a third base pair would lay the foundation for a semisynthetic organism with an expanded genetic code and also have immediate in vitro applications. Previously, the unnatural base pairs formed between d5SICS and either dNaM or dMMO2 were shown to be well-replicated by DNA polymerases under steady-state conditions and also transcribed by T7 RNA polymerase efficiently in either direction. We now demonstrate that DNA containing either the d5SICS-dNaM or d5SICS-dMMO2 unnatural base pair may be amplified by PCR with fidelities and efficiencies that approach those of fully natural DNA. These results further demonstrate that the determinants of a functional unnatural base pair may be designed into predominantly hydrophobic nucleobases with no structural similarity to the natural purines or pyrimidines. Importantly, the results reveal that the unnatural base pairs may function within an expanded genetic alphabet and make possible many in vitro applications.
用第三个碱基对扩展遗传密码子将为具有扩展遗传密码的半合成生物体奠定基础，并且也具有直接的体外应用。以前，已经证明 d5SICS 与 dNaM 或 dMMO2 之间形成的非天然碱基对在稳态条件下可以被 DNA 聚合酶很好地复制，并且可以由 T7 RNA 聚合酶有效地在任一侧转录。现在，我们证明含有 d5SICS-dNaM 或 d5SICS-dMMO2 非天然碱基对的 DNA 可以通过 PCR 进行扩增，其保真度和效率接近完全天然 DNA。这些结果进一步表明，功能非天然碱基对的决定因素可以设计到主要是疏水性碱基中，而这些碱基与天然嘌呤或嘧啶没有结构相似性。重要的是，这些结果表明非天然碱基对可能在扩展的遗传密码子中起作用，并使许多体外应用成为可能。
