APHIDICOLIN AND 1-BETA-D-ARABINOFURANOSYLCYTOSINE STRONGLY INHIBIT TRANSCRIPTIONALLY ACTIVE DNA-REPAIR IN NORMAL HUMAN FIBROBLASTS

Both aphidicolin and 1-beta-D-arabinofuranosylcytosine (araC) inactiva te DNA polymerases alpha, delta and epsilon, and accordingly block lon g-patch excision repair in mammalian cells. We report here that in nor mal human fibroblasts both compounds strongly inhibit the repair of da mage induced by UV or 4-nitroquinoline-1-oxide in the transcriptionall y active c-myc gene, as indicated by the appearance of DNA strand brea ks in carcinogen-treated cultures that were subsequently incubated in the presence of either polymerase inhibitor. We further demonstrate th at the repair of UV photoproducts in the c-myc gene can be monitored b y photolysis (313 nm) of DNA repaired in the presence of bromodeoxyuri dine (BrdUrd). In UV-irradiated cultures, the incidence of aphidicolin - or araC-accumulated strand breaks was similar to 70% of that detecte d by the BrdUrd photolysis assay. Our data therefore implicate a criti cal role for DNA polymerases alpha, delta and/or epsilon in gene-speci fic repair in human cells. The techniques described here may prove use ful in the study of DNA repair in defined sequences of the human genom e following exposure to a diverse array of physical and chemical genot oxic agents.