Malkov V A, Soyfer V N, Frank-Kamenetskii M D
Institute of Molecular Genetics, Russian Academy of Sciences, Moscow.
Nucleic Acids Res. 1992 Sep 25;20(18):4889-95. doi: 10.1093/nar/20.18.4889.
We have studied the effect of intermolecular triplexes formation on the yield of cyclobutane photodimers in DNA. DNA duplex within the pyrimidine-purine-pyrimidine triplex d(TC)nd(GA)nd(CT)n is protected from the formation of cyclobutane photodimers in the case of the stabilization of this triplex by acid pH, and in the case of supplementary stabilization by Mg2+ or Zn2+. We have studied pH-independent pyrimidine-purine-purine triplexes stabilized by bivalent cations. In such triplexes, the protection from the formation of [6-4] photodimers is observed, whereas the protection from cyclobutane dimer formation does not take place. The formation of the d(TC)nd(GA)nd(GA)n triplex leads to an inversion of the intensities of cyclobutane CT and TC photodimers. We observed a sharp decrease in photoreactivity with respect to cyclobutane dimers in the duplex tract d(C)18d(G)18 in the presence of Ba2+, Cd2+, Co2+, Mn2+, Zn2+ and Ni2+. The formation of the d(C)nd(G)nd(G)n triplex leads to 'antifootprinting', i.e. an increase in the yield of cyclobutane photodimers.
我们研究了分子间三链体形成对DNA中环丁烷光二聚体产率的影响。在嘧啶 - 嘌呤 - 嘧啶三链体d(TC)n d(GA)n d(CT)n中，当通过酸性pH稳定该三链体时，以及通过Mg2+或Zn2+进行补充稳定时，DNA双链体可免受环丁烷光二聚体的形成。我们研究了由二价阳离子稳定的与pH无关的嘧啶 - 嘌呤 - 嘌呤三链体。在这种三链体中，可观察到对[6 - 4]光二聚体形成的保护作用，而对环丁烷二聚体形成的保护作用则未发生。d(TC)n d(GA)n d(GA)n三链体的形成导致环丁烷CT和TC光二聚体强度的反转。我们观察到在存在Ba2+、Cd2+、Co2+、Mn2+、Zn2+和Ni2+的情况下，双链片段d(C)18d(G)18中环丁烷二聚体的光反应性急剧下降。d(C)n d(G)n d(G)n三链体的形成导致“反足迹”现象，即环丁烷光二聚体产率增加。
