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Yeast virology
1Laboratory of Biochemical Pharmacology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892.
Abstract:
The three families of double-stranded RNA (dsRNA) viruses and two families of retroviruses (retrotransposons) of the yeast Saccharomyces cerevisiae are all transmitted between cells only by cell fusion, probably reflecting the high frequency of mating of yeast cells in nature. One dsRNA virus and two retroviruses apparently use ribosomal "frameshifting" to produce major coat protein-polymerase fusion proteins. This mechanism allows regulation of the relative amounts of major coat protein and fusion protein that are made and avoids the possibility of mutant virus genomes being generated by splicing. Moreover, the fusion protein structure suggests a possible mechanism of genome packaging. The recent development of in vitro replication, transcription, and integration systems for these viruses, and the ease with which classical genetic and molecular studies are executed in yeast, are yielding detailed information about the roles of cellular and viral components in the viral replication cycles and the host defensive response. A host defense system against yeast dsRNA viruses is known and there is evidence to suggest a system active against the retroviruses.
Insights
Yeast viruses and retroviruses spread through cell fusion. Ribosomal frameshifting is a key mechanism for producing viral proteins, aiding replication and host defense studies.
Area of Science:
- Virology
- Molecular Biology
- Yeast Genetics
Background:
- Saccharomyces cerevisiae harbors three families of double-stranded RNA (dsRNA) viruses and two families of retroviruses.
- Transmission of these elements occurs primarily through cell fusion, common in yeast mating.
- Ribosomal frameshifting is a notable mechanism employed by some of these viruses and retroviruses.
Purpose of the Study:
- To investigate the mechanisms of viral and retroviral replication in yeast.
- To understand the role of ribosomal frameshifting in protein production for these elements.
- To explore host defense mechanisms against viral and retroviral infections in yeast.
Main Methods:
- Utilized in vitro replication, transcription, and integration systems for yeast viruses.
- Employed classical genetic and molecular studies in Saccharomyces cerevisiae.
- Analyzed viral genome structures and protein products, including fusion proteins.
Main Results:
- Identified ribosomal frameshifting as a mechanism for producing major coat protein-polymerase fusion proteins in one dsRNA virus and two retroviruses.
- Demonstrated that frameshifting regulates the production of coat proteins and fusion proteins, preventing mutant genome generation.
- The structure of fusion proteins suggests a potential mechanism for genome packaging.
Conclusions:
- Ribosomal frameshifting is a significant strategy for viral and retroviral gene expression and regulation in yeast.
- Yeast possesses defense systems against dsRNA viruses, with evidence suggesting similar systems for retroviruses.
- Ongoing research in yeast provides detailed insights into viral replication cycles and host-pathogen interactions.