Journal Article

Inhibition of Ape1 Nuclease Activity by Lead, Iron, and Cadmium

McNeill, Daniel R., Wong, Heng-Kuan, Narayana, Avinash, Wilson, David M.

2004

Overview

Many environmental metals are co-carcinogens, eliciting their effects via inhibition of DNA repair. Apurinic/apyrimidinic (AP) endonuclease 1 (Ape1) is the major mammalian abasic endonuclease and initiates repair of this cytotoxic/mutagenic lesion by incising the DNA backbone via a Mg2+-dependent reaction. In this study we examined the effects of arsenite [As(III)], cadmium [Cd(II)], cobalt [Co(II)], iron [Fe(II)], nickel [Ni(II)], and lead [Pb(II)] at concentrations ranging from 0.3 to 100 μM on the incision activity of Apel in the presence of 1 mM MgCl2. Pb(II) and Fe(II) inhibited Apel activity at each of the concentrations tested, with an IC50(half-maximal inhibitory concentration) of 0.61 and 1.0 μM, respectively. Cd(II) also inhibited Apel activity but only at concentrations > 10 μM. No inhibition was seen with As(III), Co(II), or Ni(II). A similar inhibition pattern was observed with the homologous Escherichia coli protein, exonuclease III, but no inhibition was seen with the structurally distinct AP endonuclease E. coli endonuclease IV, indicating a targeted effect of Pb(II), Fe(II), and Cd(II) on the Apel-like repair enzymes. Excess nonspecific DNA did not abrogate the metal inactivation, suggesting a protein-specific effect. Notably, Cd(II), Fe(II), and Pb(II) [but not As(III), Co(II), or Ni(II)] inhibited AP endonuclease activity in whole-cell extracts but had no significant effect on single nucleotide gap filling, 5′-flap endonuclease, and nick ligation activities, supporting the idea of selective inactivation of Apel in cells. Our results are the first to identify a potential DNA repair enzyme target for lead and suggest a means by which these prevalent environmental metals may elicit their deleterious effects.

• Publisher: National Institute of Environmental Health Sciences. National Institutes of Health. Department of Health, Education and Welfare,National Institute of Environmental Health Sciences
• Subject: Cadmium / Cadmium - toxicity / Cell Culture Techniques / Cobalt / Deoxyribonucleic acid / DNA / DNA Damage / DNA Repair / DNA-(Apurinic or Apyrimidinic Site) Lyase - pharmacology / Dose-Response Relationship, Drug / E coli / Environmental health / Enzymes / Escherichia coli - enzymology / Gene Expression Profiling / Humans / Inactivation / Iron / Iron - toxicity / Lead / Lead - toxicity / Ligation / Metals, Heavy - toxicity / Nickel / Oligonucleotides / Toxicogenomics