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  • Title: Microinjected photoreactivating enzymes from Anacystis and Saccharomyces monomerize dimers in chromatin of human cells.
    Author: Zwetsloot JC, Vermeulen W, Hoeijmakers JH, Yasui A, Eker AP, Bootsma D.
    Journal: Mutat Res; 1985 Jul; 146(1):71-7. PubMed ID: 3923332.
    Abstract:
    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.
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