title: Quantification and repair of psoralen-induced interstrand crosslinks in human cells.
abstract: Bi-functional alkylating agents that cause crosslinks are commonly used in chemotherapy. However, there is no conclusive knowledge for human cells regarding the number of induced interstrand crosslinks (ICLs) and the unhooking rate when the lesion is removed from one of the DNA strand. Using a newly developed method, we quantified the number of induced ICLs for the five furocoumarins; psoralen, 5-methoxypsoralen, 8-methoxypsoralen, tri-methoxypsoralen and angelicin. In quantitative terms, the results were in agreement with the values found by others. In kinetic studies using mammalian cells, we found that half of the psoralen-induced ICLs were unhooked within 2.5h. The rate in normal human diploid fibroblasts was found to be 20,000 ICLs/h/cell. In comparison to survival, 2500 ICLs per cell led to 50% toxicity, indicating that the unhooking of the ICLs is not the crucial step for ICL tolerance. Surprisingly, only 3500 ICLs per cell corresponded to a significant delay in the replication fork elongation. The results indicate involvements of additional pathway(s) for the delay since the effect on replication elongation could be monitored when only 10% of the replication forks encounter an ICL.
authors: Department of Molecular Biosciences, The Wenner-Gren Institute, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden. Electronic address: daniel.vare@su.se.
authors: Daniel
authors: D
authors: Vare
authors: Department of Molecular Biosciences, The Wenner-Gren Institute, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden.
authors: Fredrik
authors: F
authors: Johansson
authors: Department of Mathematics, Stockholm University, S-106 91 Stockholm, Sweden.
authors: Jan-Olov
authors: JO
authors: Persson
authors: Department of Molecular Biosciences, The Wenner-Gren Institute, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden.
authors: Klaus
authors: K
authors: Erixon
authors: Department of Molecular Biosciences, The Wenner-Gren Institute, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden.
authors: Dag
authors: D
authors: Jenssen
mesh_terms: D002460:Cell Line; D002648:Child; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D004260:DNA Repair; D011564:Furocoumarins / Q000494:pharmacology*; D006801:Humans; D008297:Male; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D011564:Furocoumarins
keywords: DNA interstrand crosslinks; DNA repair; Furocoumarins; ICL; Psoralen