BLEOMYCIN-INDUCED DNA LESIONS AT MUTATIONAL HOT-SPOTS - IMPLICATIONS FOR THE MECHANISM OF DOUBLE-STRAND CLEAVAGE

被引:153
作者
STEIGHNER, RJ [1 ]
POVIRK, LF [1 ]
机构
[1] VIRGINIA COMMONWEALTH UNIV,DEPT PHARMACOL & TOXICOL,RICHMOND,VA 23298
关键词
apurinic; apyrimidinic sites; closely opposed lesions; endonuclease III; oxidative mutagens;
D O I
10.1073/pnas.87.21.8350
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Using various end-labeled, defined-sequence DNA substrates, we examined bleomycin-induced damage at several G·C base pairs which correspond to mutational hot spots. The most frequent lesions detected were single-strand breaks and single apurinic/apyrimidinic (AP) sites at the C residue, suggesting that this was the primary site of damage. Strand breaks and AP sites also occurred, but less frequently, at a secondary damage site-i.e., the directly opposed G residue in the complementary strand. However, damage at the secondary site occurred only when a strand break was present at the primary site, and AP sites at the primary site were never accompanied by closely opposed damage in the complementary strand. Thus, formation of a strand break at the primary damage site was a necessary though not sufficient condition for attack at the secondary site. Similar patterns were seen at other sequences attacked by bleomycin, although primary and secondary sites were sometimes staggered by one nucleotide position rather than directly opposed. These and other results suggest a mechanism of double-strand cleavage in which bleomycin is reactivated during formation of the first strand break, and the reactivated drug subsequently attacks the complementary strand at a specific position which is not normally a site of bleomycin-induced cleavage. Regeneration of activated bleomycin could result from a reaction between Fe(III)·bleomycin and a 4'-peroxyl derivative of deoxyribose, both produced during formation of the strand break.
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页码:8350 / 8354
页数:5
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