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Yeast 20 S RNA replicon. Replication intermediates and encoded putative RNA polymerase
1Section on Genetics of Simple Eukaryotes, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892.
The Journal of Biological Chemistry
|July 5, 1991
Summary
Yeast 20 S RNA replication is amplified by acetate, potentially involving cAMP-dependent RNA-dependent RNA polymerase. Its circular genome structure presents unique sequencing challenges, suggesting a rolling circle replication mechanism.
Area of Science:
- Molecular Biology
- Yeast Genetics
- Virology
Background:
- The 20 S RNA is a circular single-stranded RNA replicon found in yeast.
- Its copy number dramatically increases when yeast cells are transferred to acetate medium.
- This phenomenon suggests a regulated replication process tied to nutritional status.
Purpose of the Study:
- To sequence and characterize the 20 S RNA genome.
- To investigate the mechanism behind acetate-induced amplification.
- To explore the replication strategy of the 20 S RNA.
Main Methods:
- Partial sequencing of the 20 S RNA genome.
- Bioinformatic analysis to identify open reading frames and protein homology.
- Comparison of sequence data with known viral RNA structures and replication models.
Main Results:
- Sequenced a significant portion of the 20 S RNA, revealing an open reading frame with homology to viral RNA-dependent RNA polymerases.
- Identified a cAMP-dependent phosphorylation site, suggesting a role for cAMP in acetate-induced amplification.
- Encountered difficulties in sequencing across a specific gap, indicating potential RNA structural complexities or unusual end-linkages.
- Confirmed identity with W double-stranded RNA (dsRNA), suggesting W dsRNA is the replicative form of 20 S RNA.
Conclusions:
- The 20 S RNA genome encodes a putative RNA-dependent RNA polymerase, potentially regulated by cAMP.
- The replication mechanism likely involves a rolling circle model, similar to viroids, supported by the presence of single-stranded RNA and longer-than-unit length molecules.
- The unique genomic structure poses challenges for standard sequencing techniques, hinting at novel RNA processing or ligation mechanisms.