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Inhibition of mammalian DNA polymerases by recombinant alpha-interferon and gamma-interferon
Abstract:
Interferons (IFNs) have been shown to suppress the growth of both normal and malignant cells. We examined the effect of gene-cloned IFN-alpha and IFN-gamma on the in vitro activities of human, calf, or rat DNA polymerases. IFN-alpha strongly inhibited the reactions of DNA polymerase alpha and beta at apparent Ki values of 1.25 and 0.35 x 10(5) antiviral units/ml, respectively, but inhibited DNA polymerase gamma only slightly. IFN-gamma inhibited the reaction of DNA polymerase alpha more strongly (Ki, 1.2 x 10(4) units/ml) than IFN-alpha, but not that of DNA polymerase beta. On the other hand, neither IFN-alpha nor IFN-gamma inhibited the reactions of DNA polymerase I from Escherichia coli, Klenow fragment, T-4 DNA polymerase, and RNA polymerase. The fact that Ki values for IFN-alpha of DNA polymerase from calf thymus, human leukemic cells, and rat liver were similar suggests the absence of species specificity among animals with regard to the inhibition of DNA polymerases by IFNs. These results indicate that DNA polymerase may be one of the targets of the action of IFNs.
Insights
Interferons (IFNs) inhibit DNA polymerase activity in various species. This suggests that DNA polymerase is a key target for how IFNs suppress normal and malignant cell growth.
Area of Science:
- Molecular Biology
- Biochemistry
- Immunology
Background:
- Interferons (IFNs) are known to inhibit the proliferation of both normal and cancerous cells.
- Understanding the molecular mechanisms behind IFN action is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the impact of gene-cloned Interferon-alpha (IFN-alpha) and Interferon-gamma (IFN-gamma) on the in vitro enzymatic activity of various DNA polymerases.
- To determine if DNA polymerases are among the cellular targets of IFN action.
Main Methods:
- Enzyme kinetics assays were performed to measure the inhibition of human, calf, and rat DNA polymerases (alpha, beta, gamma) by IFN-alpha and IFN-gamma.
- Bacterial and phage DNA polymerases were used as controls to assess specificity.
Main Results:
- IFN-alpha significantly inhibited DNA polymerase alpha and beta, with specific inhibition constants (Ki).
- IFN-gamma demonstrated stronger inhibition of DNA polymerase alpha compared to IFN-alpha, but did not affect DNA polymerase beta.
- Neither IFN-alpha nor IFN-gamma inhibited bacterial DNA polymerase I, Klenow fragment, T-4 DNA polymerase, or RNA polymerase.
- Similar Ki values for IFN-alpha across different species (human, calf, rat) indicate a lack of species specificity in DNA polymerase inhibition.
Conclusions:
- DNA polymerases, particularly alpha and beta, are likely targets for the growth-suppressive effects of Interferons.
- The observed lack of species specificity suggests a conserved mechanism of IFN action on DNA polymerases across mammals.
- These findings contribute to elucidating the molecular pathways through which IFNs exert their biological functions.