Demple B, Herman T, Chen D S
Department of Molecular and Cellular Toxicology, Harvard University, School of Public Health, Boston, MA 02115.
Proc Natl Acad Sci U S A. 1991 Dec 15;88(24):11450-4. doi: 10.1073/pnas.88.24.11450.
Abasic (AP) sites are common, potentially mutagenic DNA damages that are attacked by AP endonucleases. The biological roles of these enzymes in metazoans have not been tested. We have cloned the human cDNA (APE) that encodes the main nuclear AP endonuclease. The predicted Ape protein, which contains likely nuclear transport signals, is a member of a family of DNA repair enzymes that includes two bacterial AP endonucleases (ExoA protein of Streptococcus pneumoniae and exonuclease III of Escherichia coli) and Rrp1 protein of Drosophila melanogaster. Purified Ape protein lacks the 3'-exonuclease activity against undamaged DNA that is found in the bacterial and Drosophila enzymes, but the lack of obvious amino acid changes to account for this difference suggests that the various enzyme functions evolved by fine tuning a conserved active site. Expression of the active human enzyme in AP endonuclease-deficient E. coli conferred significant resistance to killing by the DNA-alkylating agent methyl methanesulfonate. The APE cDNA provides a molecular tool for analyzing the role of this central enzyme in maintaining genetic stability in humans.
脱碱基（AP）位点是常见的、具有潜在致突变性的DNA损伤，会受到AP核酸内切酶的作用。这些酶在多细胞动物中的生物学作用尚未得到验证。我们克隆了编码主要核AP核酸内切酶的人类cDNA（APE）。预测的Ape蛋白含有可能的核转运信号，是DNA修复酶家族的一员，该家族包括两种细菌AP核酸内切酶（肺炎链球菌的ExoA蛋白和大肠杆菌的核酸外切酶III）以及果蝇的Rrp1蛋白。纯化的Ape蛋白缺乏细菌和果蝇酶中存在的针对未受损DNA的3'核酸外切酶活性，但缺乏明显的氨基酸变化来解释这种差异，这表明各种酶功能是通过对保守活性位点的微调而进化的。在缺乏AP核酸内切酶的大肠杆菌中表达活性人类酶赋予了对DNA烷化剂甲磺酸甲酯杀伤的显著抗性。APE cDNA为分析这种核心酶在维持人类遗传稳定性中的作用提供了一种分子工具。
