title: The complete pattern of mutagenesis arising from the repair of site-specific psoralen crosslinks: analysis by oligonucleotide hybridization.
abstract: Psoralen crosslinks were site-specifically placed in plasmid pBR322 near the BamHI site in the tet gene by enzymatically inserting mercurated nucleotides and reacting at the target site with a sulfhydryl-containing psoralen. The damaged plasmid was repaired in SOS-induced E. coli cells. Mutants were detected by colony hybridization to oligonucleotides in the target region, and their sequences were determined. The mutations are all base substitutions, 80% transitions and 20% transversions, similar to the mutations previously identified by the loss of tetracycline resistance. However, the mutation sites detected by a physical method, unconstrained by phenotypic changes, follow a broader distribution than those identified genetically. They occur primarily at favored psoralen crosslinking sites, where T-T and T-C interstrand crosslinks can be formed. A majority of these mutations are silent.
mesh_terms: D001483:Base Sequence; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D004260:DNA Repair; D004269:DNA, Bacterial / Q000235:genetics; D005363:Ficusin / Q000494:pharmacology*; D011564:Furocoumarins / Q000494:pharmacology*; D009154:Mutation / Q000187:drug effects*; D009693:Nucleic Acid Hybridization; D010641:Phenotype; D010957:Plasmids
chemical_list: D003432:Cross-Linking Reagents; D004269:DNA, Bacterial; D011564:Furocoumarins; D005363:Ficusin