EFFECTS OF THE ENEDIYNE C-1027 ON INTRACELLULAR DNA TARGETS

We examined DNA damage induced by the enediyne-containing antitumor an tibiotic C-1027 in intracellular nuclear and mitochondrial DNA targets using the episome-containing cell line 935.1. Strand-scission activit y of the C-1027 holoantibiotic was measured by the topological forms c onversion assay in episomal and mitochondrial DNA, as well as in cell- free plasmid DNA. Genomic DNA damage was quantitated by filter elution analysis. Comparisons were made to the well-characterized enediyne ne ocarzinostatin. From these studies, mixed single- and double-strand br eaks were observed not only in cell-free, plasmid DNA but also in intr acellular episomal, mitochondrial, and genomic DNA at low nanomolar co ncentrations. C-1027 cleaved DNA 285-fold more efficiently in cells th an in a cell-free environment, and displayed preference for intracellu lar DNA species in the following rank order: episome > mitochondrial D NA >> genomic. NCS also damaged the non-histone-associated mitochondri al DNA, but not the episome. Cleavage of the 935.1 cell episome by C-1 027 occurred at specific sites including the BPV origin of replication and E6/E7 open reading frame regions, as well as the MMTV LTR promote r region.