Dayn A, Samadashwily G M, Mirkin S M
Department of Genetics, University of Illinois, Chicago 60612.
Proc Natl Acad Sci U S A. 1992 Dec 1;89(23):11406-10. doi: 10.1073/pnas.89.23.11406.
Homopurine-homopyrimidine mirror repeats are known to form intramolecular DNA triplexes in vitro. By probing with chemical agents specific for unusual DNA conformations, we have now demonstrated the formation of intramolecular triplexes consisting of G.G.C and T.A.T base triplets by DNA sequences that are neither homopurine-homopyrimidine nor mirror repeats. This finding significantly enlarges the number of sequences that could form DNA triplexes. The observed triplexes are stable under the conditions that are optimal for DNA polymerases in vitro. We found that triplex formation causes specific termination of DNA polymerization in vitro. This effect is detected for different DNA polymerases and may have implications for the regulation of DNA replication in vivo.
已知同嘌呤 - 同嘧啶镜像重复序列在体外可形成分子内DNA三链体。通过用针对异常DNA构象的化学试剂进行探测，我们现已证明，既非同嘌呤 - 同嘧啶序列也非镜像重复序列的DNA序列可形成由G.G.C和T.A.T碱基三联体组成的分子内三链体。这一发现显著增加了能够形成DNA三链体的序列数量。观察到的三链体在体外对DNA聚合酶而言最适宜的条件下是稳定的。我们发现三链体的形成会导致体外DNA聚合反应的特异性终止。不同的DNA聚合酶都能检测到这种效应，并且这可能对体内DNA复制的调控有影响。
