Wu T, Orgel L E
The Salk Institute for Biological Studies, San Diego, California 92186-5800, USA.
J Am Chem Soc. 1992;114(14):5496-501. doi: 10.1021/ja00040a002.
We have prepared hairpin oligonucleotides in which a 5'-terminal single-stranded segment contains cytidylate (C) and guanylate (G) residues. When these hairpin substrates are incubated with a mixture of cytidine 5'-phosphoro(2-methly)imidazolide (2-MeImpC) and guanosine 5'-phosphoro(2-methyl)imidazolide (2-MeImpG), the 5'-terminal segment acts as a template to facilitate sequence-specific addition of G and C residues to the 3'-terminus of the hairpin. If an isolated G residue is present at the 3'-end of the template strand, it is copied regiospecifically in the presence of 2-MeImpC and 2-MeImpG to give a product containing an isolated C residue linked to its G neighbors by 3'-5'-internucleotide bonds. However, if only 2-MeImpC is present in the reaction mixture, very little reaction occurs. Thus, the presence of 2-MeImpG catalyzes the incorporation of C. If the template strand contains a short sequence of G residues, it is copied in the presence of a mixture of 2-MeImpC and 2-MeImpG. If only 2-MeImpC is present in the reaction mixture, efficient synthesis occurs to give a final product containing one fewer C residue than the number of G residues in the template.
我们制备了发夹型寡核苷酸，其中5'-末端单链片段含有胞苷酸（C）和鸟苷酸（G）残基。当这些发夹型底物与胞苷5'-磷酰（2-甲基）咪唑酯（2-MeImpC）和鸟苷5'-磷酰（2-甲基）咪唑酯（2-MeImpG）的混合物一起温育时，5'-末端片段作为模板，促进G和C残基序列特异性地添加到发夹的3'-末端。如果模板链的3'-末端存在一个孤立的G残基，在2-MeImpC和2-MeImpG存在下，它会被区域特异性复制，得到一个产物，其中一个孤立的C残基通过3'-5'-核苷酸间键与其相邻的G残基相连。然而，如果反应混合物中仅存在2-MeImpC，则几乎不发生反应。因此，2-MeImpG的存在催化了C的掺入。如果模板链含有一段短的G残基序列，它会在2-MeImpC和2-MeImpG的混合物存在下被复制。如果反应混合物中仅存在2-MeImpC，则会发生高效合成，得到的最终产物中的C残基比模板中的G残基数量少一个。
