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Alternate poliovirus nonstructural protein processing cascades generated by primary sites of 3C proteinase cleavage
1Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine 92717.
Abstract:
The post-translational regulation of picornavirus gene expression mediated by the cascade processing of viral proteins is not well understood. Both pulse-chase studies of infected cells and in vitro studies of the translation of poliovirus type 1 RNA transcribed from genomic cDNA clones indicate a specific cascade of polyprotein processing in which the P1, P2, and P3 precursor proteins are primary products of viral proteinase cleavage. We report the results of a short-time kinetic analysis of poliovirus type 1 protein processing in an in vitro translation system and in infected HeLa cells which indicate the existence of another, rapid pathway of polyprotein processing mediated by the activity of the 3C proteinase. The observed pathway is distinct from and in addition to the one previously known. The potential role of this alternative pathway of processing in the post-translational regulation of viral gene expression is discussed.
Insights
Picornavirus gene expression involves complex protein processing. A newly discovered rapid pathway, mediated by the 3C proteinase, offers a distinct mechanism for poliovirus polyprotein processing and regulation.
Area of Science:
- Molecular Virology
- Post-translational protein modification
- Picornavirus gene expression
Background:
- Picornavirus gene expression relies on post-translational regulation through viral protein cascade processing.
- Existing models suggest primary precursor proteins (P1, P2, P3) are products of viral proteinase cleavage.
Purpose of the Study:
- To investigate the kinetics of poliovirus type 1 protein processing.
- To identify alternative pathways in viral polyprotein processing.
- To understand the regulatory role of novel processing pathways in picornavirus gene expression.
Main Methods:
- Short-time kinetic analysis of poliovirus type 1 protein processing.
- In vitro translation system using poliovirus type 1 RNA.
- Analysis of protein processing in infected HeLa cells.
Main Results:
- Identification of a rapid polyprotein processing pathway distinct from the previously known cascade.
- This alternative pathway is mediated by the activity of the 3C proteinase.
- The 3C proteinase plays a significant role in poliovirus type 1 protein processing.
Conclusions:
- A novel, rapid pathway for poliovirus polyprotein processing exists, mediated by the 3C proteinase.
- This pathway is in addition to the established cascade processing mechanism.
- The alternative pathway may play a crucial role in the post-translational regulation of picornavirus gene expression.