title: Mechanism of 2-aminopurine mutagenesis in mouse T-lymphosarcoma cells.
abstract: We investigated the mechanism of action of 2-aminopurine (Apur) in eucaryotic cells. By analogy with studies in procaryotic systems, the base analog is presumed to incorporate into DNA predominantly opposite T where, upon subsequent DNA replication, it can mispair with C, inducing an A:T leads to G:C transition. This model predicts that Apur-induced mutagenesis will be enhanced by factors that favor formation of Apur-C mispairs, e.g., high levels of dCTP or low levels of TTP. We describe the use of a mutant T-lymphosarcoma cell line, AraC-6-1, which has an abnormally high dCTP pool and a low TTP pool, to test this prediction. AraC-6-1 cells were three- to fivefold more mutable by Apur than their parental cell line, NSU-1. This enhanced mutability by Apur could not be explained by altered incorporation of 3H-labeled Apur, by generally impaired ability to repair DNA damage, or by a direct effect of Apur on the endogenous deoxynucleotide pools. The addition of 10 microM thymidine to the growth medium of AraC-6-1 cells lowered their high dCTP pool (two- to threefold), raised the TTP pool (two- to threefold), and abolished their enhanced mutability by Apur. Further manipulation to produce an abnormally high TTP/dCTP ratio suppressed Apur-induced mutagenesis (8- to 10-fold) in both AraC-6-1 and NSU-1 cells. These observations support the hypothesis that Apur induces A:T leads to G:C transitions in mammalian cells by a mispairing mechanism.
mesh_terms: D015075:2-Aminopurine / Q000494:pharmacology*; D000225:Adenine / Q000031:analogs & derivatives*; D000818:Animals; D001483:Base Sequence / Q000187:drug effects; D002460:Cell Line; D003570:Cytidine Triphosphate / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis*; D004260:DNA Repair; D004261:DNA Replication / Q000187:drug effects; D008228:Lymphoma, Non-Hodgkin; D051379:Mice; D009153:Mutagens; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D013942:Thymine Nucleotides / Q000378:metabolism
chemical_list: D009153:Mutagens; D013942:Thymine Nucleotides; D015075:2-Aminopurine; D003570:Cytidine Triphosphate; D004247:DNA; D000225:Adenine; C024157:thymidine 5'-triphosphate