Matsumoto M, Rey D A, Cory J G
Department of Internal Medicine, Univerisity of South Florida College of Medicine, H. Lee Moffitt Cancer Center and Research Institute, Tampa 33612.
Adv Enzyme Regul. 1990;30:47-59. doi: 10.1016/0065-2571(90)90008-p.
Experiments were carried out in L1210 cells to examine the importance of 'substrate cycles' in regulating the intracellular levels of deoxyribonucleoside 5'-triphosphate. L1210 cells were incubated with [14C]cytidine or [14C]adenosine in the presence and absence of hydroxyurea or cytosine arabinoside (araC). These incubations were carried out for either 30 or 120 min. Inhibition of ribonucleotide reductase by hydroxyurea resulted in the blockage of the flux of ribonucleotides to deoxyribonucleotides (greater than 90%) as expected. When DNA synthesis was inhibited with araC, there was a marked decrease in the incorporation of [14C]cytidine or [14C]adenosine into DNA as deoxyribonucleotides. However, there was not a corresponding increase in the deoxyribonucleotide levels in the acid-soluble fraction or deoxyribonucleosides in the culture medium. AraC treatment decreased the total formation of deoxyribonucleotides. These data indicate that L1210 cells do not regulate the intracellular pools of dNTPs via 'substrate cycles' which involve activation of phosphatases when DNA synthesis is blocked or activation of kinases when ribonucleotide reductase is inhibited.
在L1210细胞中进行了实验，以研究“底物循环”在调节脱氧核糖核苷5'-三磷酸细胞内水平中的重要性。在存在和不存在羟基脲或阿糖胞苷（araC）的情况下，将L1210细胞与[14C]胞苷或[14C]腺苷一起孵育。这些孵育进行30分钟或120分钟。如预期的那样，羟基脲对核糖核苷酸还原酶的抑制导致核糖核苷酸向脱氧核糖核苷酸的通量受阻（大于90%）。当用araC抑制DNA合成时，[14C]胞苷或[14C]腺苷作为脱氧核糖核苷酸掺入DNA的量显著减少。然而，酸溶性部分中的脱氧核糖核苷酸水平或培养基中的脱氧核糖核苷并没有相应增加。AraC处理降低了脱氧核糖核苷酸的总生成量。这些数据表明，L1210细胞不会通过“底物循环”来调节dNTP的细胞内池，“底物循环”包括在DNA合成受阻时磷酸酶的激活或在核糖核苷酸还原酶被抑制时激酶的激活。
