Weinberger M, Trabold P A, Lu M, Sharma K, Huberman J A, Burhans W C
Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA.
J Biol Chem. 1999 Dec 10;274(50):35975-84. doi: 10.1074/jbc.274.50.35975.
DNA damaging agents induce a conserved intra-S-phase checkpoint that inhibits DNA replication in eukaryotic cells. To better understand this checkpoint and its role in determining the efficacy of antitumor drugs that damage DNA, we examined the effects of adozelesin, a DNA-alkylating antitumor agent that has a profound inhibitory effect on initiation of DNA replication in mammals, on the replication of Saccharomyces cerevisiae chromosomes. Adozelesin inhibited initiation of S. cerevisiae DNA replication by inducing an intra-S-phase DNA damage checkpoint. This inhibitory effect was abrogated in orc2-1 cells containing a temperature-sensitive mutation in a component of the origin recognition complex (ORC) that also causes a defect in initiation. The orc2-1 mutation also caused a defect in a checkpoint that regulates the activation of origins in late S phase in cells treated with hydroxyurea. Defects in both initiation and checkpoint regulation in the orc2-1 strain were suppressed by deletion of a gene encoding a putative acetyltransferase, SAS2. Adozelesin also induced a cellular response that requires a function of ORC in G(1). A similar G(1)-specific response in mammals may contribute to the cytotoxic and antitumor properties of this and other DNA-damaging drugs.
DNA损伤剂可诱导一种保守的S期内检查点，该检查点能抑制真核细胞中的DNA复制。为了更好地理解这一检查点及其在确定损伤DNA的抗肿瘤药物疗效方面的作用，我们研究了阿多佐嗪（一种对哺乳动物DNA复制起始具有深远抑制作用的DNA烷基化抗肿瘤剂）对酿酒酵母染色体复制的影响。阿多佐嗪通过诱导S期内DNA损伤检查点来抑制酿酒酵母DNA复制的起始。在含有起源识别复合物（ORC）组分温度敏感突变的orc2-1细胞中，这种抑制作用被消除，该突变也会导致起始缺陷。orc2-1突变还导致在用羟基脲处理的细胞中，在调节S期末期起源激活的检查点中出现缺陷。orc2-1菌株中起始和检查点调节的缺陷通过缺失编码假定乙酰转移酶SAS2的基因而得到抑制。阿多佐嗪还诱导了一种在G(1)期需要ORC功能的细胞反应。哺乳动物中类似的G(1)期特异性反应可能有助于这种及其他DNA损伤药物的细胞毒性和抗肿瘤特性。
