Chaudhry M A, Dedon P C, Wilson D M, Demple B, Weinfeld M
Department of Experimental Oncology, Cross Cancer Institute, Edmonton, AB, Canada.
Biochem Pharmacol. 1999 Mar 1;57(5):531-8. doi: 10.1016/s0006-2952(98)00327-x.
DNA strand breaks with terminal 3'-phosphoglycolate groups are produced by agents that can abstract the hydrogen atom from the 4'-carbon of DNA deoxyribose groups. Included among these agents are gamma-radiation (via the OH radical) and enediyne compounds, such as neocarzinostatin and calicheamicin. However, while the majority of radiation-induced phosphoglycolates are found at single-strand breaks, most of the phosphoglycolates generated by these two enediynes are found at bistranded lesions, including double-strand breaks. Using a 32P-post-labelling assay, we have compared the enzyme-catalyzed removal of phosphoglycolates induced by each of these agents. Both human apurinic/apyrimidinic endonuclease 1 (Ape 1) and its Escherichia coli homolog exonuclease III rapidly removed over 80% of phosphoglycolates from gamma-irradiated DNA, although there appeared to be a small resistant subpopulation. The neocarzinostatin-induced phosphoglycolates were removed more slowly, though not to completion, while the calicheamicin-induced phosphoglycolates were extremely refractory to both enzymes. These data suggest that unless other enzymes are capable of acting upon the phosphoglycolate termini at enediyne-induced double-strand breaks, such termini will be resistant to end rejoining repair pathways.
带有末端3'-磷酸乙醇酸基团的DNA链断裂是由能够从DNA脱氧核糖基团的4'-碳上提取氢原子的试剂产生的。这些试剂包括γ射线（通过OH自由基）和烯二炔化合物，如新制癌菌素和刺孢霉素。然而，虽然大多数辐射诱导的磷酸乙醇酸存在于单链断裂处，但这两种烯二炔产生的大多数磷酸乙醇酸存在于双链损伤处，包括双链断裂。使用32P后标记分析法，我们比较了这些试剂各自诱导的磷酸乙醇酸的酶促去除情况。人脱嘌呤/脱嘧啶内切酶1（Ape 1）及其大肠杆菌同源物核酸外切酶III都能迅速从γ射线照射的DNA中去除80%以上的磷酸乙醇酸，尽管似乎有一小部分具有抗性的亚群。新制癌菌素诱导的磷酸乙醇酸去除得较慢，虽然没有完全去除，而刺孢霉素诱导的磷酸乙醇酸对这两种酶都极具抗性。这些数据表明，除非其他酶能够作用于烯二炔诱导的双链断裂处的磷酸乙醇酸末端，否则这些末端将对末端重接修复途径具有抗性。
