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Mol. Cell. Biol., 12 1997, 6822-6830, Vol 17, No. 12
T Bessho, D Mu and A Sancar
Most DNA repair mechanisms rely on the redundant information inherent to
the duplex to remove damaged nucleotides and replace them with normal ones,
using the complementary strand as a template. Interstrand cross-links pose
a unique challenge to the DNA repair machinery because both strands are
damaged. To study the repair of interstrand cross- links by mammalian
cells, we tested the activities of cell extracts of wild-type or excision
repair-defective rodent cell lines and of purified human excision nuclease
on a duplex with a site-specific cross- link. We found that in contrast to
monoadducts, which are removed by dual incisions bracketing the lesion, the
cross-link causes dual incisions, both 5' to the cross-link in one of the
two strands. The net result is the generation of a 22- to
28-nucleotide-long gap immediately 5' to the cross-link. This gap may act
as a recombinogenic signal to initiate cross-link removal.
Copyright © 1997, American Society for Microbiology
Initiation of DNA interstrand cross-link repair in humans: the nucleotide excision repair system makes dual incisions 5' to the cross- linked base and removes a 22- to 28-nucleotide-long damage-free strand
Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill 27599, USA.
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