J Biol Chem, Vol. 274, Issue 42, 29740-29743, October 15, 1999
Cytosine Arabinoside Lesions Are Position-specific Topoisomerase
II Poisons and Stimulate DNA Cleavage Mediated by the Human Type II
Enzymes
Susan D.
Cline
and
Neil
Osheroff
¶
From the Departments of
Biochemistry and
¶ Medicine (Hematology/Oncology), Vanderbilt University School of
Medicine, Nashville, Tennessee 37232-0146
Cytosine arabinoside (araC) is an important drug
used for the treatment of human leukemias. In order to exert its
cytotoxic effects, araC must be incorporated into chromosomal DNA.
Although specific DNA lesions that involve base loss or modification
stimulate nucleic acid cleavage mediated by type II topoisomerases, the effects of deoxyribose sugar ring modification on enzyme activity have
not been examined. Therefore, the effects of incorporated araC residues
on the DNA cleavage/religation equilibrium of human topoisomerase II
and
were characterized. AraC lesions were position-specific
topoisomerase II poisons and stimulated DNA scission mediated by both
human type II enzymes. However, the positional specificity of araC
residues differed from that previously reported for other
cleavage-enhancing DNA lesions. Finally, additive or synergistic
increases in DNA cleavage were observed in the presence of araC lesions
and etoposide. These findings broaden the range of DNA lesions known to
alter topoisomerase II function and raise the possibility that this
enzyme may mediate some of the cellular effects of araC.
Copyright © 1999 by The American Society for Biochemistry and Molecular Biology, Inc.