Open AccessUltraviolet-induced mutations in Cockayne syndrome cells are primarily caused by cyclobutane dimer photoproducts while repair of other photoproducts is normal.
Author(s) -
Christopher N. Parris,
Kenneth H. Kraemer
Publication year - 1993
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.90.15.7260
Subject(s) - pyrimidine dimer , xeroderma pigmentosum , shuttle vector , cyclobutane , photolyase , mutagenesis , dna repair , microbiology and biotechnology , transfection , mutation , plasmid , mutation frequency , cockayne syndrome , biology , dna damage , ultraviolet light , chemistry , dna , cell culture , photochemistry , genetics , gene , recombinant dna , ring (chemistry) , organic chemistry , vector (molecular biology)
We compared the contribution to mutagenesis in Cockayne syndrome (CS) cells of the major class of UV photoproducts, the cyclobutane pyrimidine dimer, to that of other DNA photoproducts by using the mutagenesis shuttle vector pZ189. Lymphoblastoid cell lines from the DNA repair-deficient disorders CS and xeroderma pigmentosum (XP) and a normal line were transfected with UV-treated pZ189. Cyclobutane dimers were selectively removed before transfection by photoreactivation (PR), leaving nondimer photoproducts intact. After UV exposure and replication in CS and XP cells, plasmid survival was abnormally reduced and mutation frequency was abnormally elevated. After PR, plasmid survival increased and mutation frequency in CS cells decreased to normal levels but remained abnormal in XP cells. Sequence analysis of > 200 mutant plasmids showed that with CS cells a major mutational hot spot was caused by unrepaired cyclobutane dimers. These data indicate that with both CS and XP cyclobutane dimers are major photoproducts generating reduced plasmid survival and increased mutation frequency. However, unlike XP, CS cells are proficient in repair of nondimer photoproducts. Since XP but not CS patients have a high frequency of UV-induced skin cancers, our data suggest that prevention of UV-induce skin cancers is associated with proficient repair of nondimer photoproducts.