P. Pourquier et al., Induction of topoisomerase I cleavage complexes by 1-beta-D-arabinofuranosylcytosine (ara-C) in vitro and in ara-C-treated cells, P NAS US, 97(4), 2000, pp. 1885-1890
Citations number
42
Categorie Soggetti
Multidisciplinary
Journal title
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
1-beta-D-Arabinofuranosylcytosine (Ara-C) is a nucleoside analog commonly u
sed in the treatment of leukemias. Ara-C inhibits DNA polymerases and can b
e incorporated into DNA, Its mechanism of cytotoxicity is not fully underst
ood. Using oligonucleotides and purified human topoisomerase I (top1), we f
ound a 4- to 6-fold enhancement of top1 cleavage complexes when ara-e was i
ncorporated at the +1 position (immediately 3') relative to a unique top1 c
leavage site. This enhancement was primarily due to a reversible inhibition
of top1-mediated DNA religation. Because ara-C incorporation is known to a
lter base stacking and sugar puckering at the misincorporation site and at
the neighboring base pairs, the observed inhibition of religation at the ar
a-C site suggests the importance of the alignment of the 5'-hydroxyl end fo
r religation with the phosphate group of the top1 phosphotyrosine bond. Thi
s study also demonstrates that ara-C treatment and DNA incorporation trap t
op1 cleavage complexes in human leukemia cells. Finally, we report that cam
ptothecin-resistant mouse P388/ CPT45 cells with no detectable top1 are cro
ssresistant to ara-C, which suggests that top1 poisoning is a potential mec
hanism for ara-C cytotoxicity.