title: SV40 DNA replication inhibition by the monofunctional DNA alkylator Et743.
abstract: Ecteinascidin 743 (Et743) is a highly cytotoxic anticancer agent isolated from the squirt Ecteinascidia turbinate, which alkylates DNA in the minor groove at GC-rich sequences resulting in an unusual bending toward the major groove. The ability of Et743 to block DNA replication was studied using the well-established simian virus (SV40) model for mammalian DNA replication in cells and cell-free extracts. Intracellular SV40 DNA isolated from Et743-treated BSC-1 cells was analyzed by native, two-dimensional agarose gel electrophoresis. A low frequency of Et743 adducts detected at 30-100 nM drug concentrations inhibited SV40 origin activity and induced formation of unusual DNA replication intermediates. Under cell-free conditions, only a high Et743 adduct frequency reduced SV40 DNA synthesis. Comparative studies involving related DNA alkylators, tomamycin and saframycin A, revealed inhibition of SV40 DNA replication in cells at concentrations approximately 10 times higher than Et743. Under cell-free conditions tomamycin- or saframycin-A-adducted DNA templates inhibited DNA synthesis similarly to Et743. Et743 appears to be unusual among other alkylators, because its adducts strongly inhibit intracellular SV40 DNA replication but are relatively weak as cis inhibitors as measured under cell-free conditions.
authors.affiliation: Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, New York 14263, USA.
authors.forename: Barbara
authors.initials: B
authors.lastname: Dziegielewska
authors.forename: David
authors.initials: D
authors.lastname: Kowalski
authors.forename: Terry A
authors.initials: TA
authors.lastname: Beerman
mesh_terms: D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D000998:Antiviral Agents / Q000494:pharmacology*; D001569:Benzodiazepines / Q000494:pharmacology; D002460:Cell Line; D002474:Cell-Free System / Q000187:drug effects; D002522:Chlorocebus aethiops; D018736:DNA Adducts / Q000032:analysis; D004261:DNA Replication / Q000187:drug effects*; D004279:DNA, Viral / Q000032:analysis / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D004149:Dioxoles / Q000494:pharmacology*; D005090:Exodeoxyribonucleases / Q000737:chemistry; D045325:HCT116 Cells; D006801:Humans; D007424:Intracellular Fluid / Q000737:chemistry; D007546:Isoquinolines / Q000494:pharmacology*; D011758:Pyrroles / Q000494:pharmacology; D013539:Simian virus 40 / Q000187:drug effects / Q000235:genetics*; D015719:Single-Strand Specific DNA and RNA Endonucleases / Q000737:chemistry; D013698:Templates, Genetic; D044005:Tetrahydroisoquinolines; D000077606:Trabectedin; D014561:Urochordata; D014779:Virus Replication / Q000187:drug effects*
chemical_list: D018906:Antineoplastic Agents, Alkylating; D000998:Antiviral Agents; D018736:DNA Adducts; D004279:DNA, Viral; D004149:Dioxoles; D007546:Isoquinolines; D011758:Pyrroles; D044005:Tetrahydroisoquinolines; C438462:pyrrolo(2,1-c)(1,4)benzodiazepine; D001569:Benzodiazepines; D005090:Exodeoxyribonucleases; C020133:exodeoxyribonuclease III; D015719:Single-Strand Specific DNA and RNA Endonucleases; D000077606:Trabectedin