Asymmetry in forming 2-aminopurine · hydroxymethylcytosine heteroduplexes; a model giving misincorporation frequencies and rounds of DNA replication from base-pair populations in vivo

Hopkins, Randi L.; Goodman, Myron F.

doi:10.1016/0022-2836(79)90337-1

Cited by 20 publications

(11 citation statements)

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“…Nor was the AraC-6-1 cell line generally impaired in its ability to repair DNA, as evidenced by its normal sensitivity to mutagenesis by the alkylating agent MNNG. We reasoned that, as predicted by one hypothesis (1,12,14,27), the perturbed TTP and dCTP pools were responsible for the increased mutability of AraC-61 cells by Apur. This was verified by pharmacologically manipulating the dCTP and TTP pools by adding thymidine to the growth medium.…”

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confidence: 92%

“…In procaryotes, Apur is usually incorporated into DNA opposite T and induces A:T --G:C transitions by mispairing with C in a subsequent round of DNA replication. Apur can also induce G:C --A:T transitions, although with a much lower frequency, by being erroneously incorporated into DNA opposite C and then pairing with T (6,12,14,23). Apur has been reported to induce mutations in mammalian cells (2,5).…”

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confidence: 99%

“…However, the mechanism of mutagenic action of Apur in eucaryotic systems is less clear. It has been suggested that in addition to its well-documented base-pairing ambiguity (10,14,23), Apur may be mutagenic by a second mechanism involving perturbation of deoxynucleotide triphosphate (dNTP) pools (15). Bromodeoxyuridine, the other well-studied mutagenic base analog, is also believed to exert twofold effects (15,20).…”

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confidence: 99%

“…We conclude that the levels of TTP, and possibly also dCTP, modulate the level of mutagenesis induced by Apur. DISCUSSION Two mechanisms have been proposed for Apur-induced mutagenesis, one involving base mispairing (10,14,23) and the other involving perturbation of endogenous dNTP pools (15). Since a mutant mouse lymphoma cell line (AraC-6-1) containing an abnormally high dCTP pool and a low TIP pool was available, we were able to test both of the proposed mechanisms.…”

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confidence: 99%

“…One hypothesis, based on in vivo studies with procaryotes (1,12,14,23) and in vitro studies with purified DNA polymerases and synthetic templates (27) (6). This hypothesis predicts that the concentrations of the endogenous substrates dCTP and TTP will be an important factor influencing Apur-induced mutagenesis.…”

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confidence: 99%

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Mechanism of 2-aminopurine mutagenesis in mouse T-lymphosarcoma cells.

Caras¹,

MacInnes²,

Persing³

et al. 1982

Mol. Cell. Biol.

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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.

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confidence: 92%

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confidence: 99%