Lin George C, Jaeger Joachim, Eckert Kristin A, Sweasy Joann B
Department of Therapeutic Radiology and Genetics, Yale University School of Medicine, 333 Cedar St., New Haven, CT 06520, USA.
DNA Repair (Amst). 2009 Feb 1;8(2):182-9. doi: 10.1016/j.dnarep.2008.10.006. Epub 2008 Dec 5.
Loop II of DNA polymerase beta (pol beta) consists of 14 amino acid residues and is highly flexible and solvent exposed. Previous research from our laboratory has shown that this loop is important for polymerase activity and fidelity. In the study presented here, we demonstrate that a shortened five amino acid residue loop compromises the fidelity of pol beta. This five-residue loop, termed ENEYP, induces one base frameshift errors and A-C transversions within a specific sequence context. We demonstrate that ENEYP misincorporates dGTP opposite template A at higher efficiencies than wild-type pol beta. The kinetic basis for misincorporation is a defect in discrimination of the correct from incorrect dNTP substrate at the level of ground-state binding. Our results are consistent with the idea that loop II of pol beta functions to maintain accurate DNA synthesis by a direct or indirect influence on the nucleotide binding pocket.
DNA聚合酶β（polβ）的环II由14个氨基酸残基组成，具有高度的灵活性且暴露于溶剂中。我们实验室之前的研究表明，该环对聚合酶活性和保真度很重要。在本文所呈现的研究中，我们证明缩短为五个氨基酸残基的环会损害polβ的保真度。这个被称为ENEYP的五残基环在特定序列背景下会引发一个碱基移码错误和A-C颠换。我们证明，ENEYP在与模板A相对时错误掺入dGTP的效率高于野生型polβ。错误掺入的动力学基础是在基态结合水平上对正确与错误dNTP底物的区分存在缺陷。我们的结果与以下观点一致，即polβ的环II通过对核苷酸结合口袋的直接或间接影响来维持准确的DNA合成。
