Sinden R R, Hashem V I, Rosche W A
Department of Biochemistry and Biophysics, Texas A&M University, Houston 77030-3303, USA.
Ann N Y Acad Sci. 1999 May 18;870:173-89. doi: 10.1111/j.1749-6632.1999.tb08878.x.
The fidelity of replication has evolved to reproduce B-form DNA accurately, while allowing a low frequency of mutation. The fidelity of replication can be compromised, however, by defined order sequence DNA (dosDNA) that can adopt unusual or non B-DNA conformations. These alternative DNA conformations, including hairpins, cruciforms, triplex DNAs, and slipped-strand structures, may affect enzyme-template interactions that potentially lead to mutations. To analyze the effect of dosDNA elements on spontaneous mutagenesis, various mutational inserts containing inverted repeats or direct repeats were cloned in a plasmid containing a unidirectional origin of replication and a selectable marker for the mutation. This system allows for analysis of mutational events that are specific for the leading or lagging strands during DNA replication in Escherichia coli. Deletions between direct repeats, involving misalignment stabilized by DNA secondary structure, occurred preferentially on the lagging strand. Intermolecular strand switch events, correcting quasipalindromes to perfect inverted repeats, occurred preferentially during replication of the leading strand.
复制保真度已经进化到能够精确复制B型DNA，同时允许低频突变。然而，复制保真度可能会受到特定顺序序列DNA（dosDNA）的影响，这种DNA可以呈现异常或非B型DNA构象。这些替代DNA构象，包括发夹、十字形、三链DNA和滑链结构，可能会影响酶与模板的相互作用，从而潜在地导致突变。为了分析dosDNA元件对自发诱变的影响，将各种含有反向重复或直接重复的突变插入片段克隆到一个含有单向复制起点和突变选择标记的质粒中。该系统允许分析在大肠杆菌DNA复制过程中前导链或后随链特有的突变事件。涉及由DNA二级结构稳定的错配的直接重复之间的缺失，优先发生在后随链上。分子间链交换事件，即将准回文校正为完美的反向重复，优先发生在前导链复制过程中。
