Bleomycin-induced alterations in DNA replication: relationship to DNA damage.
Bleomycin (BLM), a well-known DNA scission agent, is assumed to inhibit intracellular DNA replication by damaging the DNA template (cis-acting mechanism), although other DNA damaging compounds can alter DNA replication through modulation of crucial replication factor(s) (trans-acting mechanism). The present study examines the relationship between DNA damage and inhibition of replication caused by BLM in the well-defined simian virus 40 (SV40) intracellular and cell-free in vitro systems. Treatment of SV40-infected BSC-1 cells for 2 h with BLM at 50 microg/mL, induced 0.3 break/viral genome. Under the same treatment conditions, analysis of replication intermediates on two-dimensional gels showed a decrease in both mass of SV40 replication intermediates and replication activity. The mass of SV40 intermediates was decreased to about 30%, whereas replication activity was reduced to less than 5%. These results suggest that BLM inhibits both initiation and elongation phases of SV40 replication. In a cell-free DNA replication system, extracts from BLM-treated cells (50 micro/mL) were able to support SV40 DNA replication by only 50%. In this study, non-drug-treated DNA template was used, implying that BLM can induce a trans-acting effect. Finally, the drug-induced effects on SV40 DNA replication in cell-free and intracellular viral systems were compared to the effects on genomic DNA replication in BSC-1 cells. Overall, the results support the concept that BLM-induced inhibition of DNA replication occurs by both trans- (inhibition of replication of nondamaged template) and cis-acting mechanisms (template damage).
Dziegielewski
J
J
Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, New York 14263, USA.
Melendy
T
T
Beerman
T A
TA
D000818:Animals; D000957:Antigens, Viral, Tumor / Q000235:genetics; D001761:Bleomycin / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D002460:Cell Line / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000821:virology; D002474:Cell-Free System / Q000187:drug effects / Q000378:metabolism / Q000821:virology; D002522:Chlorocebus aethiops; D004249:DNA Damage; D004261:DNA Replication / Q000187:drug effects*; D004279:DNA, Viral / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D006131:Growth Inhibitors / Q000494:pharmacology; D007364:Intercalating Agents / Q000494:pharmacology*; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism / Q000821:virology; D013539:Simian virus 40 / Q000235:genetics
D000957:Antigens, Viral, Tumor; D004279:DNA, Viral; D006131:Growth Inhibitors; D007364:Intercalating Agents; D001761:Bleomycin