Effects of nickel ions on polymerase activity and fidelity during DNA replication in vitro.
Nickel is a genotoxic carcinogen. However, the mechanisms of nickel-induced genotoxicity are not well understood. We have investigated the effects of Ni2+ ions on DNA polymerase activity and the fidelity of DNA replication in vitro. The effect of Ni2+ on different DNA polymerases is quite variable. The amount of enzyme inhibition and degree of alteration in replication fidelity induced by Ni2+ are dependent both on the polymerase and its associated 3'-5' exonuclease activity. Some polymerases, such as E. coli DNA polymerase I, AMV reverse transcriptase and human DNA polymerase alpha, can utilize Ni2+ as a weak substitute for Mg2+ during DNA replication. Other polymerases are very sensitive to inhibition by Ni2+ and the IC50 can vary by an order of magnitude. T4 polymerase is relatively insensitive to inhibition by Ni2+, although the sensitivity is enhanced in the absence of added Mg2+, and Ni preferentially inhibits the 3'-5' exonuclease function of T7 DNA polymerase. The fidelity and processivity of DNA polymerases may be either increased or decreased by Ni ions in a polymerase dependent manner. The inhibition DNA polymerase activity and altered replication fidelity may contribute significantly to Ni-induced mutagenesis and genotoxicity in vivo.
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Nelson Institute of Environmental Medicine, New York University Medical Center, Tuxedo 10987.
Xu
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Kinney
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D017931:DNA Primers / Q000378:metabolism; D004261:DNA Replication / Q000187:drug effects* / Q000502:physiology; D004259:DNA-Directed DNA Polymerase / Q000187:drug effects*; D005092:Exonucleases / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D007477:Ions; D008274:Magnesium / Q000494:pharmacology; D009532:Nickel / Q000494:pharmacology* / Q000633:toxicity; D019384:Nucleic Acid Synthesis Inhibitors; D009711:Nucleotides / Q000378:metabolism; D013698:Templates, Genetic
D017931:DNA Primers; D007477:Ions; D019384:Nucleic Acid Synthesis Inhibitors; D009711:Nucleotides; D009532:Nickel; D004259:DNA-Directed DNA Polymerase; D005092:Exonucleases; D008274:Magnesium