INHIBITION OF INITIATION OF SIMIAN-VIRUS-40 DNA-REPLICATION IN INFECTED BSC-1 CELLS BY THE DNA ALKYLATING DRUG ADOZELESIN

Adozelesin is a member of a family of extraordinarily cytotoxic DNA da maging agents that bind to the DNA minor groove in a sequence-specific manner and form covalent adducts with adenines. Previous studies empl oying purified enzymes and adozelesin-modified template DNAs suggested that adozelesin-DNA adducts inhibit DNA replication at the level of n ascent DNA chain elongation. In this study, neutral/neutral two-dimens ional agarose gel electrophoresis was employed to analyze simian virus 40 (SV40) DNA replication intermediates recovered from adozelesin-tre ated SV40 virus-infected cells. SV40 replication intermediates rapidly disappeared from infected cells when they were treated with adozelesi n, but not when the cells were also treated with aphidicolin to block maturation of replicating SV40 DNA. We conclude that the disappearance of SV40 replication intermediates induced by adozelesin treatment was a consequence of maturation of these intermediates in the absence of new initiation events. Adozelesin inhibition of nascent chain elongati on is first observed at concentrations above those needed to block ini tiation. Adozelesin treatment inhibits SV40 DNA replication at concent rations that produce adducts on just a small fraction of the intracell ular population of SV40 DNA molecules.