Mammalian DNA polymerases α, β, γ, δ and ε incorporate fialuridine (FTAU) monophosphate into DNA and are inhibited competitively by FTAU triphosphate

Eli Lilly, Indianapolis, Indiana, United States
Biochemistry (Impact Factor: 3.01). 01/1995; 33(48):14620-4. DOI: 10.1021/bi00252a030
Source: PubMed

ABSTRACT 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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    • " 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. "
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