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.

0 (Chromatin), 0 (Pyrimidine Dimers), Cells, Cultured, Chromatin/*drug effects, Cyanobacteria/enzymology, DNA Repair/*drug effects/radiation effects, Deoxyribodipyrimidine Photo-Lyase/*pharmacology, EC 4. (Lyases), EC (Deoxyribodipyrimidine Photo-Lyase), Fibroblasts/drug effects/metabolism, Human, Lyases/*pharmacology, Microinjections, Pyrimidine Dimers/*metabolism, Saccharomyces cerevisiae/enzymology, Support, Non-U.S. Gov't
Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis
Erasmus MC: University Medical Center Rotterdam

Zwetsloot, J.C.M, Vermeulen, W, Hoeijmakers, J.H.J, Yasui, A, Eker, A.P.M, & Bootsma, D. (1985). Microinjected photoreactivating enzymes from Anacystis and Saccharomyces monomerize dimers in chromatin of human cells. Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis, 146, 71–77. Retrieved from