DNA-DAMAGING ENEDIYNE C-1027 INHIBITS INITIATION OF INTRACELLULAR SV40 DNA-REPLICATION IN TRANS

This study used 2-D agarose gel techniques to examine the effects of t he DNA-strand scission enediyne C-1027 on DNA replication in SV40-infe cted BSC-1 cells. Replication of SV40 DNA was inhibited by C-1027 to a greater extent than was BSC-1 genomic DNA replication in infected cel ls. Low nanomolar concentrations (0.2-10 nM) of C-1027 affected a rapi d, progressive decrease in SV40 replication activity and replication i ntermediates (RIs) within 15 min after drug addition. A concurrent dec rease in the signal of both the SV40 bubble are and replication activi ty with increasing concentrations of C-1027 suggested that C-1027 inhi bited initiation of new RIs. Additionally, the reduction in bubble are signal observed with C-1027 was prevented when elongation of nascent chains was blocked by aphidicolin. Thus, the C-1027-induced disappeara nce of RIs probably is related to the maturation of preformed replicat ion molecules in the absence of initiation of new RIs. Strand damage t o SV40 DNA was barely detectable at concentrations where inhibition of replication activity was nearly complete, indicating that C-1027 repl ication inhibition occurs in trans.