Related Experiment Videos
Abstract:
Polyoma-infected mouse kidney cell cultures were labeled with [(3)H]uridine for 3 h late in the lytic cycle (26 to 29 h after infection) and RNA was extracted from cytoplasm and nuclei and from isolated polyribosomes. Sedimentation velocity analysis in sucrose gradients showed that polyoma-specific "giant" and 26S RNAs are present exclusively in the nucleus. RNA associated with cytoplasmic polyribosomes was analyzed by sedimentation in aqueous sucrose density gradients and dimethylsulfoxide sucrose gradients, as well as by polyacrylamide gel electrophoresis. Polyoma-specific RNA in polyribosomes consists of at least two classes, with sedimentation coefficients of 16 (major fraction) and 19S (minor fraction) in aqueous sucrose gradients and 15 and 17S, respectively, in dimethylsulfoxide gradients. Estimates based on dimethylsulfoxide gradient and analysis suggest a molecular weight of approximately 500,000 for 16S RNA and 700,000 for 19S RNA. These polyoma RNAs seem to undergo reversible conformational changes under the different conditions of analysis. We cannot exclude the possibility that they contain more than one molecular species.
Insights
Researchers identified distinct polyoma-specific RNA molecules in the cytoplasm of infected mouse kidney cells. These RNAs, found on polyribosomes, suggest specific roles in viral protein synthesis during the lytic cycle.
Area of Science:
- Molecular Biology
- Virology
- Cell Biology
Background:
- Polyomaviruses are small DNA viruses that replicate in the nucleus of infected cells.
- Understanding viral RNA processing and translation is crucial for deciphering viral replication strategies.
Purpose of the Study:
- To characterize polyoma-specific RNA molecules present in the cytoplasm of infected mouse kidney cells.
- To determine the size, location, and potential conformational properties of these RNAs.
Main Methods:
- Infection of mouse kidney cell cultures with polyomavirus.
- Labeling cells with [(3)H]uridine during the late lytic cycle.
- Extraction of RNA from cellular compartments (nucleus, cytoplasm) and isolated polyribosomes.
- Analysis of RNA using sedimentation velocity in sucrose gradients (aqueous and DMSO) and polyacrylamide gel electrophoresis.
Main Results:
- Polyoma-specific "giant" and 26S RNAs were exclusively found in the nucleus.
- Cytoplasmic polyribosomes contained two major classes of polyoma-specific RNA, with sedimentation coefficients of 16S and 19S (aqueous sucrose) or 15S and 17S (DMSO sucrose).
- Estimated molecular weights for these cytoplasmic RNAs were approximately 500,000 (16S) and 700,000 (19S).
- Observed reversible conformational changes in polyoma RNAs under different analytical conditions.
Conclusions:
- Polyoma-specific RNAs found in cytoplasmic polyribosomes are distinct from nuclear RNAs.
- These cytoplasmic RNAs likely play a role in viral protein synthesis.
- The findings suggest complex RNA processing and potential conformational flexibility in polyomavirus gene expression.