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Structural basis for activation of alpha-boranophosphate nucleotide analogues targeting drug-resistant reverse
P Meyer1, B Schneider, S Sarfati
1Laboratoire d'Enzymologie et Biochimie Structurales, UPR-9063 CNRS, 91198 Gif-sur-Yvette, France.
Abstract:
AIDS chemotherapy is limited by inadequate intracellular concentrations of the active triphosphate form of nucleoside analogues, leading to incomplete inhibition of viral replication and the appearance of drug-resistant virus. Drug activation by nucleoside diphosphate kinase and inhibition of HIV-1 reverse transcriptase were studied comparatively. We synthesized analogues with a borano (BH(3)(-)) group on the alpha-phosphate, and found that they are substrates for both enzymes. X-ray structures of complexes with nucleotide diphosphate kinase provided a structural basis for their activation. The complex with d4T triphosphate displayed an intramolecular CH.O bond contributing to catalysis, and the R(p) diastereoisomer of thymidine alpha-boranotriphosphate bound like a normal substrate. Using alpha-(R(p))-boranophosphate derivatives of the clinically relevant compounds AZT and d4T, the presence of the alpha-borano group improved both phosphorylation by nucleotide diphosphate kinase and inhibition of reverse transcription. Moreover, repair of blocked DNA chains by pyrophosphorolysis was reduced significantly in variant reverse transcriptases bearing substitutions found in drug-resistant viruses. Thus, the alpha-borano modification of analogues targeting reverse transcriptase may be of generic value in fighting viral drug resistance.
Insights
New borano-modified nucleoside analogues enhance AIDS chemotherapy by improving drug activation and HIV-1 reverse transcriptase inhibition. These modifications also reduce drug resistance, offering a promising strategy against viral resistance.
Area of Science:
- Biochemistry
- Virology
- Medicinal Chemistry
Background:
- AIDS chemotherapy faces challenges due to low intracellular concentrations of active nucleoside analogue triphosphates.
- This leads to incomplete viral replication inhibition and the emergence of drug-resistant HIV-1 strains.
Purpose of the Study:
- To investigate drug activation by nucleoside diphosphate kinase and inhibition of HIV-1 reverse transcriptase.
- To explore the potential of alpha-borano modified nucleoside analogues in overcoming limitations in AIDS chemotherapy and drug resistance.
Main Methods:
- Synthesis of nucleoside analogues with a borano group on the alpha-phosphate.
- Enzymatic assays to study substrate activity for nucleoside diphosphate kinase and HIV-1 reverse transcriptase.
- X-ray crystallography to determine the structural basis of enzyme-analogue interactions.
- Evaluation of drug-resistant reverse transcriptase variants.
Main Results:
- Borano-modified analogues are substrates for both nucleoside diphosphate kinase and HIV-1 reverse transcriptase.
- X-ray structures revealed the mechanism of activation and substrate binding.
- The alpha-borano group enhanced phosphorylation and reverse transcriptase inhibition for AZT and d4T analogues.
- Reduced pyrophosphorolysis by resistant reverse transcriptases was observed.
Conclusions:
- Alpha-borano modification improves the efficacy of nucleoside analogues against HIV-1.
- This modification shows potential in combating drug-resistant viral strains.
- The strategy may offer a generic approach to enhance antiviral therapies.