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.
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.
Bessho
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Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill 27599, USA.
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Sancar
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D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D003432:Cross-Linking Reagents; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage; D011088:DNA Ligases / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair / Q000235:genetics / Q000502:physiology*; D004270:DNA, Circular / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins; D011564:Furocoumarins; D006801:Humans; D007364:Intercalating Agents; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D013347:Subcellular Fractions / Q000378:metabolism; D013379:Substrate Specificity
D003432:Cross-Linking Reagents; D004270:DNA, Circular; D029968:Escherichia coli Proteins; D011564:Furocoumarins; D007364:Intercalating Agents; D004247:DNA; D004706:Endodeoxyribonucleases; C036385:endodeoxyribonuclease uvrABC; D011088:DNA Ligases