Van Den Neste Eric, Smal Caroline, Cardoen Sabine, Delacauw Anne, Frankard Joëlle, Ferrant Augustin, Van den Berghe Georges, Bontemps Françoise
Laboratory of Physiological Chemistry, Christian de Duve Institute of Cellular Pathology, Avenue Hippocrate 75, UCL-ICP 7539, B-1200 Brussels, Belgium.
Biochem Pharmacol. 2003 Feb 15;65(4):573-80. doi: 10.1016/s0006-2952(02)01559-9.
Deoxycytidine kinase (dCK), a key enzyme of the deoxynucleoside salvage pathway, might have a preponderant role in DNA synthesis in resting chronic lymphocytic leukemia B-lymphocytes. In these cells, two important enzymes in deoxynucleoside triphosphate production, ribonucleotide reductase and thymidine kinase (TK), both cell-cycle regulated, are indeed very weakly expressed. This study investigated the regulation of dCK activity in response to UV-C light, a condition which causes DNA lesions and DNA repair synthesis. We observed that activity of dCK in B-CLL cells was upregulated up to 3-fold, 30 min after irradiation with 30 J/m(2) UV-C, whereas TK activity was unchanged. Activation of dCK by UV-C light was caused neither by a change in concentration of a low molecular weight metabolite nor by an increase in the amount of dCK protein. Activation of dCK by UV-C was mimicked by H(2)O(2), markedly counteracted by N-acetylcysteine, a general antioxidant, and completely abolished by the growth factor receptor inhibitor suramin. Taken together, these results indicate that dCK activity is upregulated by UV-C light through a postranslational modification that may be initiated at the cell surface through oxidative mechanisms. Suramin also suppressed the increase in DNA repair synthesis elicited by UV-C irradiation, suggesting that upregulation of dCK activity could contribute to the normal completion of DNA repair synthesis elicited by UV light.
脱氧胞苷激酶（dCK）是脱氧核苷补救途径的关键酶，可能在静止的慢性淋巴细胞白血病B淋巴细胞的DNA合成中起主要作用。在这些细胞中，脱氧核苷三磷酸生成过程中的两种重要酶，即核糖核苷酸还原酶和胸苷激酶（TK），二者均受细胞周期调控，实际上表达非常微弱。本研究调查了dCK活性对紫外线C（UV-C）照射的反应调节，UV-C照射会导致DNA损伤和DNA修复合成。我们观察到，在用30 J/m²的UV-C照射后30分钟，B-CLL细胞中的dCK活性上调至3倍，而TK活性未发生变化。UV-C光对dCK的激活既不是由低分子量代谢物浓度的变化引起的，也不是由dCK蛋白量的增加引起的。UV-C对dCK的激活可被过氧化氢模拟，被一般抗氧化剂N-乙酰半胱氨酸显著抵消，并被生长因子受体抑制剂苏拉明完全消除。综上所述，这些结果表明，UV-C光通过一种可能在细胞表面通过氧化机制启动的翻译后修饰上调dCK活性。苏拉明还抑制了UV-C照射引起的DNA修复合成增加，表明dCK活性的上调可能有助于UV光引起的DNA修复合成的正常完成。
