Ohno Y, Spriggs D, Matsukage A, Ohno T, Kufe D
Laboratory of Clinical Pharmacology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115.
Cancer Res. 1988 Mar 15;48(6):1494-8.
1-beta-D-Arabinofuranosylcytosine (ara-C) is an effective antileukemic agent which acts as an inhibitor of DNA synthesis. The precise mechanism responsible for this inhibitory effect, however, remains unclear. The present work has examined the effects of the triphosphate derivative, ara-CTP, on purified DNA polymerase beta. These studies were performed on M13 phage DNA templates of defined sequence. The results demonstrate that ara-C is incorporated into DNA by DNA polymerase beta. The results also demonstrate that the incorporated ara-C residue acts as a relative chain terminator. Moreover, the relative chain terminating effects of ara-C are sequence specific. In this regard, DNA strand elongation was progressively slowed at sequences of two, three, and four contiguous sites for cytosine incorporation. We also demonstrate that the inhibitory effects of ara-C are reversed by competition with deoxycytidine-triphosphate for incorporation into the DNA strand. Taken together, these findings are consistent with structural differences of the incorporated arabinosyl moiety which alter reactivity of the 3'-terminus and thereby inhibit chain elongation. These findings also provide new insights regarding the inhibitory effects of ara-C on elongation of specific DNA sequences.
1-β-D-阿拉伯呋喃糖基胞嘧啶（阿糖胞苷，ara-C）是一种有效的抗白血病药物，它作为DNA合成的抑制剂发挥作用。然而，导致这种抑制作用的确切机制仍不清楚。目前的研究考察了三磷酸衍生物阿糖胞苷三磷酸（ara-CTP）对纯化的DNA聚合酶β的影响。这些研究是在特定序列的M13噬菌体DNA模板上进行的。结果表明，阿糖胞苷被DNA聚合酶β掺入到DNA中。结果还表明，掺入的阿糖胞苷残基起到相对链终止剂的作用。此外，阿糖胞苷的相对链终止作用具有序列特异性。在这方面，在连续两个、三个和四个胞嘧啶掺入位点的序列处，DNA链延伸逐渐减慢。我们还证明，通过与脱氧胞苷三磷酸竞争掺入DNA链，阿糖胞苷的抑制作用可被逆转。综上所述，这些发现与掺入的阿拉伯糖基部分的结构差异一致，这些差异改变了3'-末端的反应性，从而抑制链延伸。这些发现也为阿糖胞苷对特定DNA序列延伸的抑制作用提供了新的见解。
