Bessho T, Mu D, Sancar A
Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill 27599, USA.
Mol Cell Biol. 1997 Dec;17(12):6822-30. doi: 10.1128/MCB.17.12.6822.
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.
大多数DNA修复机制依赖于双链中固有的冗余信息，以去除受损核苷酸并用正常核苷酸取代它们，以互补链为模板。链间交联对DNA修复机制构成了独特的挑战，因为两条链都受到了损伤。为了研究哺乳动物细胞对链间交联的修复，我们测试了野生型或切除修复缺陷型啮齿动物细胞系的细胞提取物以及纯化的人切除核酸酶对具有位点特异性交联的双链的活性。我们发现，与通过在损伤两侧进行双重切割而去除的单加合物不同，交联会导致双重切割，两条链之一中交联位点的5'端都会发生切割。最终结果是在交联位点的5'端立即产生一个22至28个核苷酸长的缺口。这个缺口可能作为一个重组信号来启动交联的去除。
