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Alterations of protein synthesis in arbovirus-infected L cells
Abstract:
Lust, George (Fort Detrick, Frederick, Md.). Alterations of protein synthesis in arbovirus-infected L cells. J. Bacteriol. 91:1612-1617. 1966.-Cellular protein synthesis and ribonucleic acid (RNA) synthesis in mouse L cells were markedly depressed 1 hr after infection with Venezuelan equine encephalomyelitis virus. Host RNA and protein synthesis were inhibited more rapidly by the virus infection than by actinomycin D. In cells infected 4 hr, a cytoplasmic RNA polymerase was demonstrated which was absent in uninfected cells. At this time, deoxyribonucleic acid-directed RNA synthesis catalyzed by the nuclear RNA polymerase was inhibited in vitro in enzyme preparations from nuclei of virus-infected cells. For optimal activity, the cytoplasmic RNA polymerase required the four nucleoside triphosphates, Mg(++), and RNA. The enzyme was insensitive to actinomycin D and deoxyribonuclease, indicating that it catalyzed RNA-directed RNA synthesis. Attempts to purify the induced polymerase further were unsuccessful. Fresh preparations had to be used because the enzymatic activity was unstable.
Insights
Venezuelan equine encephalomyelitis virus rapidly inhibits host protein and RNA synthesis in L cells. An RNA-directed RNA polymerase, absent in normal cells, appears after infection.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Arboviruses, such as Venezuelan equine encephalomyelitis virus (VEEV), can significantly impact host cell functions.
- Understanding viral mechanisms that disrupt host macromolecular synthesis is crucial for antiviral research.
- Previous studies indicated VEEV infection affects cellular protein and RNA synthesis.
Purpose of the Study:
- To investigate the effects of VEEV infection on host cell protein and RNA synthesis.
- To identify and characterize novel enzymes involved in RNA synthesis during VEEV infection.
Main Methods:
- Infection of mouse L cells with VEEV.
- Measurement of host cellular protein and ribonucleic acid (RNA) synthesis.
- Assay of RNA polymerase activity in cell extracts.
- In vitro characterization of enzyme properties, including substrate requirements and sensitivity to inhibitors.
Main Results:
- VEEV infection markedly depressed host RNA and protein synthesis within 1 hour.
- Host synthesis inhibition by VEEV was faster than that induced by actinomycin D.
- A cytoplasmic RNA polymerase, absent in uninfected cells, was detected 4 hours post-infection.
- Nuclear deoxyribonucleic acid-directed RNA synthesis was inhibited in infected cells.
- The induced cytoplasmic enzyme catalyzed RNA-directed RNA synthesis and was insensitive to actinomycin D.
Conclusions:
- VEEV infection rapidly disrupts host cell macromolecular synthesis.
- VEEV induces a novel cytoplasmic RNA polymerase responsible for RNA-directed RNA synthesis.
- This induced polymerase plays a key role in viral replication, distinct from host nuclear transcription.