Microinjected photoreactivating enzymes from Anacystis and Saccharomyces monomerize dimers in chromatin of human cells

Mutat Res. 1985 Jul;146(1):71-7. doi: 10.1016/0167-8817(85)90057-4.


Photoreactivating enzymes (PRE) from the yeast Saccharomyces cerevisiae and the cyanobacterium Anacystis nidulans have been injected into the cytoplasm of repair-proficient human fibroblasts in culture. After administration of photoreactivation light, PRE-injected cells displayed a significantly lower level of UV-induced unscheduled DNA synthesis (UDS) than non-injected cells. This indicates that monomerization of the UV-induced pyrimidine dimers in the mammalian chromatin had occurred as a result of photoreactivation by the injected PRE at the expense of repair by the endogenous excision pathway. Purified PRE from yeast is able to reduce UDS to 20-25% of the UDS found in non-injected cells, whereas the in vitro more active PRE from A. nidulans gives a reduction to only 70%. This suggests that the eukaryotic enzyme is more efficient in the removal of pyrimidine dimers from mammalian chromatin than its equivalent purified from the prokaryote A. nidulans.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cells, Cultured
  • Chromatin / drug effects*
  • Cyanobacteria / enzymology
  • DNA Repair / drug effects*
  • DNA Repair / radiation effects
  • Deoxyribodipyrimidine Photo-Lyase / pharmacology*
  • Fibroblasts / drug effects
  • Fibroblasts / metabolism
  • Humans
  • Lyases / pharmacology*
  • Microinjections
  • Pyrimidine Dimers / metabolism*
  • Saccharomyces cerevisiae / enzymology


  • Chromatin
  • Pyrimidine Dimers
  • Lyases
  • Deoxyribodipyrimidine Photo-Lyase