Relationship between pyrimidine dimers, 6-4 photoproducts, repair synthesis and cell survival: studies using cells from patients with trichothiodystrophy

Mutat Res. 1990 Jan;235(1):33-40. doi: 10.1016/0921-8777(90)90020-6.


Trichothiodystrophy is a genetic disease which in the majority of cases studied is associated with a deficiency in the ability to repair UV damage in cellular DNA. Three categories of UV response have been identified. In type 1 the response is completely normal, whereas type 2 cells are deficient in excision-repair, with properties indistinguishable from those of XP complementation group D. Type 3 cells have normal survival following UV-irradiation and normal rates of removal of cyclobutane pyrimidine dimer sites. Nevertheless repair synthesis is reduced by 50% in these cell strains and this is associated with a marked reduction in the repair of 6-4 photoproducts from cellular DNA. The present results show that 50% or more of repair synthesis at early times after irradiation of normal primary human fibroblasts is attributable to repair of 6-4 products. They also suggest that repair of cyclobutane dimers is crucial for cell survival.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Survival / radiation effects
  • Cells, Cultured
  • Child, Preschool
  • DNA / radiation effects*
  • DNA Repair*
  • Female
  • Fibroblasts / radiation effects
  • Hair Diseases / genetics*
  • Humans
  • Pyrimidine Dimers / metabolism*
  • Ultraviolet Rays


  • Pyrimidine Dimers
  • DNA