Mammalian DNA Polymerases .alpha., .beta., .gamma., .delta., and .epsilon. Incorporate Fialuridine (FIAU) Monophosphate into DNA and Are Inhibited Competitively by FIAU Triphosphate

Eli Lilly, Indianapolis, Indiana, United States
Biochemistry (Impact Factor: 3.02). 01/1995; 33(48):14620-4. DOI: 10.1021/bi00252a030
Source: PubMed


Fialuridine [FIAU, 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5- iodouridine] was used in clinical trials for chronic hepatitis B virus infection and was extremely toxic. Evidence suggested targets of FIAU toxicity included mitochondria, but toxic mechanisms were unclear. Since FIAU is a thymidine analog, we reasoned that triphosphorylated FIAU (FIAUTP) could be incorporated into mitochondrial DNA by DNA pol-gamma and into genomic DNA by DNA polymerases alpha, beta, delta, and epsilon. All five purified mammalian DNA polymerases incorporated FIAUMP into the nascent DNA chain during in vitro DNA synthesis. When FIAUTP was substituted for dTTP, oligonucleotide products were generated efficiently by DNA pol-gamma and were similar to those generated in the presence of the four normal dNTPs. In contrast, oligonucleotide products generated by the four nuclear DNA polymerases in the presence of FIAUTP were significantly reduced in length relative to those generated in the presence of dTTP. In parallel kinetic assays, FIAUTP competitively inhibited the accumulation of radiolabeled dTTP into DNA by DNA pol-gamma. The Ki with DNA pol-gamma was 0.04 microM, the lowest Ki among the mammalian DNA polymerases. Competition between FIAUTP and dTTP and the relative ease of accumulation of FIAUMP in mitochondrial DNA by DNA pol-gamma in vitro together may relate to clinical FIAU toxicity.

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    • "Most of the NRTI-induced mitochondrial toxicity results from the activity of the mtDNA polymerase g (pol g), which incorporates the nucleoside analogs into mtDNA, leading to chain termination and inhibition of mtDNA replication. Furthermore, pol g is unique among the cellular replicative DNA polymerases in that it is also highly sensitive to inhibition by NRTIs [Parker et al., 1991; Copeland et al., 1992; Hart et al., 1992; Huang et al., 1992; Nickel et al., 1992; Lewis et al., 1994; Martin et al., 1994; Eriksson et al., 1995; Johnson et al., 2001; Lim and Copeland, 2001]. Inhibition of the exonuclease activity of pol g is mediated at least in part by AZT-monophosphate at concentrations known to occur within cells [Lim and Copeland , 2001]. "
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    Environmental and Molecular Mutagenesis 04/2007; 48(3-4):190-200. DOI:10.1002/em.20191 · 2.63 Impact Factor
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    • " The study of the interaction between dideoxynucleotides and human DNA polymerases shows no affinity of these nucleo - tides for the a or the e species , a low but detectable in - teraction with the b - polymerase ( Ono et al . , 1989 ; Yarchoan et al . , 1989 ) and a significant inhibitory activity against g - polymerase ( Brinkman et al . 1998 ; Lewis et al . , 1994 ; Lewis Table 1 Current NRTI regimen therapies to reduce mother - to - child transmission"
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    • "This suggests that the NRTI monophosphate is incorporated into mtDNA. FIAU, FIAC (1-[2-deoxy-2-fluoro-␤-D- arabinofuranosyl]-5-iodocytosine), FMAU (1-[2-deoxy-2- fluoro-␤-D-arabinofuranosyl]-5-methyluracil), and FEAU (1- [2-deoxy-2-fluoro-␤-D-arabinofuranosyl]-5-ethyluracil) each demonstrated efficacy in viral disease models (Fourel et al, 1990), and many of their triphosphates inhibit mammalian DNA pol-␥ in vitro (Lewis et al, 1994a). With these agents, competition with the native nucleotide and NRTI at the nucleotide binding site of DNA pol-␥ appears to be a critical event. "

    Laboratory Investigation 07/2001; 81(6):777-90. DOI:10.1038/labinvest.3780288 · 3.68 Impact Factor
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