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Inhibition of influenza virus transcription by 2'-deoxy-2'-fluoroguanosine
Abstract:
The nucleoside analog 2'-deoxy-2'-fluoroguanosine (2'-fluorodGuo) is phosphorylated by cellular enzymes and reversibly inhibits influenza virus replication in chick embryo cells within the first 4 h of infection. RNA hybridization studies revealed that primary and secondary transcription of influenza virus RNA were blocked at a compound concentration of 10 microM, but no inhibition of cell protein synthesis was seen even at high compound concentrations (200 microM). In vitro, the triphosphate of 2'-fluorodGuo is a competitive inhibitor of influenza virus transcriptase activity from disrupted virus, with a Ki of 1.0 microM. The cellular polymerases DNA polymerase alpha and RNA polymerase II were only weakly inhibited or were insusceptible to 2'-fluorodGTP. In kinetic studies with the influenza virus transcriptase, 2'-fluorodGTP, in the absence of GTP, blocked elongation of the virus RNA chain. Similarly, by using purified ribonucleoprotein complexes it was found that the addition of a single nucleotide of 2'-fluorodGTP to the virus RNA caused chain termination, which resulted in the blockage of further virus transcription. Furthermore, the specificity for influenza virus transcriptase was confirmed when the transcriptase from partially resistant virus was found to be 10-fold less susceptible to 2'-fluorodGTP (Ki = 13.1 microM).
Insights
2'-deoxy-2'-fluoroguanosine (2'-fluorodGuo) inhibits influenza virus replication by blocking RNA transcription. This nucleoside analog specifically targets viral transcriptase, halting RNA chain elongation without affecting host cell protein synthesis.
Area of Science:
- Virology
- Molecular Biology
- Antiviral Research
Background:
- Influenza virus replication relies on its unique RNA transcriptase.
- Developing specific antiviral agents is crucial for combating influenza infections.
Purpose of the Study:
- To investigate the antiviral activity of 2 -deoxy-2 -fluoroguanosine (2 -fluorodGuo) against influenza virus.
- To elucidate the mechanism of action of 2 -fluorodGuo on viral RNA synthesis.
Main Methods:
- Cell-based assays in chick embryo cells to assess viral replication inhibition.
- RNA hybridization studies to analyze viral RNA transcription.
- In vitro enzyme kinetics using purified influenza virus transcriptase and cellular polymerases.
Main Results:
- 2 -fluorodGuo effectively inhibited influenza virus replication and RNA transcription at 10 microM.
- The triphosphate form (2 -fluorodGTP) competitively inhibited viral transcriptase (Ki = 1.0 microM) but not cellular polymerases.
- 2 -fluorodGTP acted as a chain terminator for viral RNA synthesis, blocking elongation.
Conclusions:
- 2 -fluorodGuo is a potent inhibitor of influenza virus transcription.
- Its specificity for viral transcriptase suggests potential as a targeted antiviral therapy.
- The mechanism involves competitive inhibition and chain termination of viral RNA synthesis.