Johnson Sean J, Beese Lorena S
Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
Cell. 2004 Mar 19;116(6):803-16. doi: 10.1016/s0092-8674(04)00252-1.
Accurate DNA replication is essential for genomic stability. One mechanism by which high-fidelity DNA polymerases maintain replication accuracy involves stalling of the polymerase in response to covalent incorporation of mismatched base pairs, thereby favoring subsequent mismatch excision. Some polymerases retain a "short-term memory" of replication errors, responding to mismatches up to four base pairs in from the primer terminus. Here we a present a structural characterization of all 12 possible mismatches captured at the growing primer terminus in the active site of a polymerase. Our observations suggest four mechanisms that lead to mismatch-induced stalling of the polymerase. Furthermore, we have observed the effects of extending a mismatch up to six base pairs from the primer terminus and find that long-range distortions in the DNA transmit the presence of the mismatch back to the enzyme active site, suggesting the structural basis for the short-term memory of replication errors.
准确的DNA复制对于基因组稳定性至关重要。高保真DNA聚合酶维持复制准确性的一种机制涉及到聚合酶因错配碱基对的共价掺入而停滞，从而有利于随后的错配切除。一些聚合酶保留了复制错误的“短期记忆”，可对引物末端起四个碱基对范围内的错配做出反应。在此，我们展示了在聚合酶活性位点的生长引物末端捕获的所有12种可能错配的结构特征。我们的观察结果表明了导致聚合酶错配诱导停滞的四种机制。此外，我们观察到了将错配从引物末端延伸至六个碱基对的影响，并发现DNA中的长程扭曲将错配的存在传递回酶活性位点，这表明了复制错误短期记忆的结构基础。
