Ringer D P, Howell B A, Etheredge J L, Clouse J A, Kizer D E
Samuel Roberts Noble Foundation, Inc., Ardmore, OK 73402.
FEBS Lett. 1987 Nov 16;224(1):59-64. doi: 10.1016/0014-5793(87)80422-2.
The organization of specific pyrimidine pathways to channel various nucleoside precursors into DNA is poorly understood. We show that concanavalin A-stimulated guinea pig lymphocytes incorporate [3H]dThd, [3H]dCyd, [3H]dUrd, [3H]Cyd and [3H]Urd into DNA-thymines and DNA-cytosines in a highly conserved distribution pattern. DNA-thymines were labeled only by dThd and dUrd, while DNA-cytosines were labeled only by dCyd, Cyd and Urd. The kinetics for the incorporation of the [3H]nucleosides were essentially identical, indicating equivalent abilities to measure DNA synthesis. Pyrazofurin inhibition of the pyrimidine de novo synthetic pathway inhibited cell proliferation and the levels of [3H]nucleoside incorporation by approx. 50%, but did not alter restricted distribution of the [3H]nucleosides among DNA-thymines and DNA-cytosines. These findings indicate the absence of Cyd and dCMP deaminase salvage pathways and suggest either subcellular compartmentalization or differential regulation of ribonucleoside diphosphoreductase which permits reduction of CDP but not UDP.
将各种核苷前体导入DNA的特定嘧啶途径的组织方式目前了解甚少。我们发现，伴刀豆球蛋白A刺激的豚鼠淋巴细胞以高度保守的分布模式将[3H]胸苷、[3H]胞苷、[3H]尿苷、[3H]胞嘧啶核苷和[3H]尿嘧啶核苷掺入DNA胸腺嘧啶和DNA胞嘧啶中。DNA胸腺嘧啶仅由胸苷和尿苷标记，而DNA胞嘧啶仅由胞苷、胞嘧啶核苷和尿苷标记。[3H]核苷掺入的动力学基本相同，表明测量DNA合成的能力相当。吡唑呋林对嘧啶从头合成途径的抑制作用抑制了细胞增殖以及[3H]核苷掺入水平约50%，但并未改变[3H]核苷在DNA胸腺嘧啶和DNA胞嘧啶之间的受限分布。这些发现表明不存在胞嘧啶核苷和脱氧胞苷酸脱氨酶补救途径，并提示要么存在亚细胞区室化，要么存在核糖核苷二磷酸还原酶的差异调节，这使得胞苷二磷酸能够被还原而尿苷二磷酸不能。
