DNA ADENINE ADDUCTS INDUCED BY NITROGEN MUSTARDS AND THEIR ROLE IN TRANSCRIPTION TERMINATION INVITRO
DNA ADENINE ADDUCTS INDUCED BY NITROGEN MUSTARDS AND THEIR ROLE IN TRANSCRIPTION TERMINATION INVITRO
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DOI：
10.1093/carcin/11.10.1739
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发表时间：
1990-10-01
期刊：
影响因子：
4.7
通讯作者：
ERICKSON, LC
中科院分区：
文献类型：
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作者：
PIEPER, RO;ERICKSON, LC
先前的研究已经证明，三种氮芥类癌症化疗化合物，梅法尔(L-PAM)，氮芥酸(HN_2)和氯氨丁苯(CBC)，每一种都会产生DNA损伤，提前终止体外转录。这些病变的部位与这些化合物形成的N7鸟嘌呤单加合物的部位不一致，在L病例中，PAM和CBC提示腺嘌呤病变。本研究试图鉴定和鉴定氮芥末诱导的非N7鸟嘌呤DNA加合物，特别是腺嘌呤DNA加合物，并评估它们在药物诱导的体外转录终止中的作用。使用改进的马克萨姆-吉尔伯特DNA测序技术的研究数据表明，L-PAM和CBC，而不是HN2，在所研究的特定DNA模板区域的几乎每个腺嘌呤上都产生不稳定的、碱稳定的腺嘌呤加合物。在同一模板中比较L-PAM和CBc诱导腺嘌呤加合物的转录终止位点，发现L-PAM和CBc诱导的转录终止与药物诱导的单个腺嘌呤损伤无关，而与药物诱导的相邻腺嘌呤加合物相关。此外，利用聚合酶链式反应介导的DNA扩增产生的小分子的体外转录研究表明，L-PAM和CBc在该分子中诱导的转录终止损伤都不是链间的。这些结果表明，一些(但不是全部)氮芥子化合物可以在DNA中产生不热不稳定的腺嘌呤损伤，可以形成热不稳定的腺嘌呤加合物的双功能氮芥菜也可以形成与链内腺嘌呤-腺嘌呤交联物一致的加合物。在体外，这些腺嘌呤加合物似乎是L-PAM和CBC诱导的转录终止的原因。
Previous studies have demonstrated that three cancer chemotherapeutic compounds of the nitrogen mustard class, melphalal (L-PAM), nitrogen mustard (HN2) and chlorambucil (CBC), each generated DNA lesions that prematurely terminate in vitro transcription. Sites of these lesions were inconsistent with sites of N7 guanine monoadducts formed by these compounds, and in the cases of L-PAM and CBC were suggestive of adenine lesions. The present study is an attempt to identify and characterize nitrogen mustard-induced non-N7 guanine DNA adducts, and in particular adenine DNA adducts, and to assess their role in drug-induced in vitro transcription termination. Data from studies using a modified Maxam-Gilbert DNA sequencing technique demonstrate that L-PAM and CBC, but not HN2, generate heat-labile, alkaline-stabilized adenine adducts at nearly every adenine in a region of a defined DNA template examined. Comparison of sites of L-PAM- and CBC-induced adenine adducts to know sites of drug-induced transcription termination in the same DNA template show that L-PAM- and CBC-induced transcription termination is associated not with drug lesions at single adenine, but rather with drug-induced adducts at neighboring adenines. Additional in vitro transcription studies using a small DNA molecule generated by polymerase chain reaction-mediated DNA amplification demonstrate that none of the transcription-terminating lesions induced by L-PAM and CBC in this molecule are interstrand in nature. These results suggest that some, but not all, nitrogen mustard compounds can generate heat-labile adenine lesions in DNA, and that bifunctional nitrogen mustards that can form heat labile adenine adducts also form adducts consistent with intrastrand adenine-adenine crosslinks. These adducts at pairs of adenines in turn appear to be responsible for L-PAM-and CBC-induced transcription termination in vitro.