title: Primer RNA chain termination induced by 9-beta-D-arabinofuranosyl-2-fluoroadenine 5'-triphosphate. A mechanism of DNA synthesis inhibition.
abstract: The studies described herein were aimed at defining the mechanism by which 9-beta-D-arabinofuranosyl-2-fluoroadenine 5'-triphosphate (FaraATP), the active intracellular metabolite of fludarabine phosphate, inhibits the synthesis of primer RNA and RNA-primed DNA by the polymerase alpha-primase complex. Incubation of the purified DNA polymerase alpha-primase complex with a poly(dT) template, 500 microM ATP, and increasing concentrations of FaraATP from 2.5 to 50 microM resulted in the progressive accumulation of smaller oligoribonucleotides (2-6 nucleotides) at the expense of the full-length products of DNA primase (7-10 nucleotides). Comparison of the kcat/KM values for incorporation of FaraATP and ATP into oligoribonucleotides revealed that DNA primase incorporated FaraATP 30-fold more efficiently than ATP. FaraAMP was present exclusively at the 3'-termini of the growing primer RNA chains, which prevented further elongation of the primers by DNA primase (primer RNA chain termination). At all FaraATP concentrations tested, inhibition of RNA-primed DNA synthesis was accompanied by primer chain termination. In contrast, DNA polymerase alpha added FaraATP onto full-length primer RNAs about 8-fold less efficiently than dATP, and the incorporation of FaraAMP at the 3'-termini of the primers did not prevent further elongation of these primers by DNA polymerase alpha. These results indicate that primer RNA chain termination is the major effect responsible for the inhibition of RNA-primed DNA synthesis by fludarabine phosphate.
authors.affiliation: Department of Biochemistry, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27157.
authors.forename: C V
authors.initials: CV
authors.lastname: Catapano
authors.forename: F W
authors.initials: FW
authors.lastname: Perrino
authors.forename: D J
authors.initials: DJ
authors.lastname: Fernandes
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis*; D004257:DNA Polymerase II / Q000037:antagonists & inhibitors; D019915:DNA Primase; D006801:Humans; D009843:Oligoribonucleotides / Q000096:biosynthesis; D012313:RNA / Q000096:biosynthesis*; D012316:RNA Nucleotidyltransferases / Q000037:antagonists & inhibitors; D013698:Templates, Genetic; D014407:Tumor Cells, Cultured; D001084:Vidarabine Phosphate / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology
chemical_list: D009843:Oligoribonucleotides; D001084:Vidarabine Phosphate; C000101:ara-ATP; D012313:RNA; D000255:Adenosine Triphosphate; D004247:DNA; D019915:DNA Primase; D012316:RNA Nucleotidyltransferases; D004257:DNA Polymerase II