Bae Soo In, Zhao Ran, Snapka Robert M
Department of Radiology, Division of Radiobiology, The Ohio State University, Columbus, OH 43240, United States.
Biochem Pharmacol. 2008 Dec 15;76(12):1653-68. doi: 10.1016/j.bcp.2008.09.003. Epub 2008 Sep 6.
Structurally diverse chemotherapeutic and chemopreventive drugs, including camptothecin, doxorubicin, sanguinarine, and others, were found to cause covalent crosslinking of proliferating cell nuclear antigen (PCNA) trimers in mammalian cells exposed to fluorescent light. This PCNA damage was caused by both nuclear and cytoplasmically localizing drugs. For some drugs, the PCNA crosslinking was evident even with very brief exposures to laboratory room lighting. In the absence of drugs, there was no detectable covalent crosslinking of PCNA trimers. Other proteins were photo-crosslinked to PCNA at much lower levels, including crosslinking of additional PCNA to the PCNA trimer. The proteins photo-crosslinked to PCNA did not vary with cell type or drug. PCNA was not crosslinked to itself or to other proteins by superoxide, hydrogen peroxide or hydroxyl radicals, but hydrogen peroxide caused monoubiquitination of PCNA. Quenching of PCNA photo-crosslinking by histidine, and enhancement by deuterium oxide, suggest a role for singlet oxygen in the crosslinking. SV40 large T antigen hexamers were also efficiently covalently photo-crosslinked by drugs and light. Photodynamic crosslinking of nuclear proteins by cytoplasmically localizing drugs, together with other evidence, argues that these drugs may reach the nucleoplasm in amounts sufficient to photodamage important chromosomal enzymes. The covalent crosslinking of PCNA trimers provides an extremely sensitive biomarker for photodynamic damage. The damage to PCNA and large T antigen raises the possibility that DNA damage signaling and repair mechanisms may be compromised when cells treated with antineoplastic drugs are exposed to visible light.
结构多样的化疗和化学预防药物，包括喜树碱、阿霉素、血根碱等，被发现会在暴露于荧光的哺乳动物细胞中导致增殖细胞核抗原（PCNA）三聚体的共价交联。这种PCNA损伤是由细胞核和细胞质定位的药物共同引起的。对于某些药物，即使在实验室室内光线下短暂暴露，PCNA交联也很明显。在没有药物的情况下，未检测到PCNA三聚体的共价交联。其他蛋白质与PCNA的光交联水平要低得多，包括额外的PCNA与PCNA三聚体的交联。与PCNA光交联的蛋白质不会因细胞类型或药物而有所不同。超氧化物、过氧化氢或羟基自由基不会使PCNA自身交联或与其他蛋白质交联，但过氧化氢会导致PCNA单泛素化。组氨酸对PCNA光交联的淬灭作用以及氧化氘对其的增强作用表明单线态氧在交联中起作用。SV40大T抗原六聚体也能被药物和光有效地共价光交联。细胞质定位的药物对核蛋白的光动力交联以及其他证据表明，这些药物可能以足以光损伤重要染色体酶的量进入核质。PCNA三聚体的共价交联为光动力损伤提供了一个极其敏感的生物标志物。PCNA和大T抗原的损伤增加了这样一种可能性，即当用抗肿瘤药物治疗的细胞暴露于可见光时，DNA损伤信号传导和修复机制可能会受到损害。
