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A mouse cell line, which is unprotected by interferon against lytic virus infection, lacks ribonuclease F activity
Abstract:
A mouse cell line, NIH 3T3, does not respond to some of the activities of interferon. Even after treatment with high concentrations of interferon the replication of lytic viruses, such as encephalomyocarditis virus (EMCV) and vesicular stomatitis virus (VSV) is not inhibited in these cells. In contrast, interferon treatment of these same cells results in the inhibition of Moloney murine leukemia virus (MMuLV) production. We have analyzed enzymatic pathways which are induced by interferon in these cells. After interferon treatment, the level of the (2'-5')oligoadenylate [(2'-5)An] synthetase activity and the phosphorylation of the 67000-dalton protein (P1) are enhanced in NIH 3T3 cells to approximately the same level as interferon-sensitive mouse L-cells. Moreover, NIH 3T3 and L-cells, contain approximately the same levels of enzymes which inactivate (2'-5')An. Both exogenously added (2'-5')A3 or double-stranded RNA (dsRNA) failed to inhibit protein synthesis in NIH 3T3 extracts even though they were potent inhibitors of L-cell extract-directed protein synthesis. Direct measurements of the (2'-5')An-dependent ribonuclease F (RNase F) failed to detect such activity in NIH 3T3 cells. Our results, therefore, suggest that the presence of RNase F activity is necessary for the interferon-induced antiviral activity against EMCV and against VSV. The induction of protein kinase activity by interferon treatment of NIH 3T3 cells appears to have no direct effect on EMCV and VSV replication.
Insights
NIH 3T3 cells lack a key enzyme, RNase F, which is essential for interferon to inhibit lytic virus replication. This finding clarifies interferon
Area of Science:
- Virology
- Immunology
- Molecular Biology
Background:
- Interferon (IFN) is a crucial antiviral cytokine.
- Mouse NIH 3T3 cells exhibit differential responses to IFN treatment.
- Understanding IFN-induced antiviral mechanisms is vital for therapeutic development.
Purpose of the Study:
- To investigate the molecular basis for NIH 3T3 cell resistance to certain IFN antiviral activities.
- To analyze the enzymatic pathways induced by IFN in NIH 3T3 cells.
- To determine the role of (2'-5')oligoadenylate [(2'-5')An] synthetase and RNase F in IFN-mediated antiviral defense.
Main Methods:
- Treatment of NIH 3T3 cells with interferon.
- Assay of (2'-5')oligoadenylate [(2'-5')An] synthetase and protein kinase activities.
- Analysis of protein synthesis inhibition by (2'-5')A3 and double-stranded RNA (dsRNA).
- Measurement of (2'-5')An-dependent ribonuclease F (RNase F) activity.
Main Results:
- NIH 3T3 cells showed enhanced (2'-5')An synthetase and protein kinase activities after IFN treatment, similar to sensitive L-cells.
- Exogenous (2'-5')A3 and dsRNA failed to inhibit protein synthesis in NIH 3T3 cell extracts.
- Crucially, RNase F activity was undetectable in NIH 3T3 cells.
- Interferon treatment did not inhibit encephalomyocarditis virus (EMCV) and vesicular stomatitis virus (VSV) replication in NIH 3T3 cells.
Conclusions:
- The absence of RNase F activity in NIH 3T3 cells explains their lack of response to interferon's antiviral effects against EMCV and VSV.
- RNase F is a necessary component for interferon-induced antiviral activity.
- Protein kinase induction by interferon does not directly impact EMCV and VSV replication in these cells.