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Template-dependent initiation of Sindbis virus RNA replication in vitro
J A Lemm1, A Bergqvist, C M Read
1Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110-1093, USA.
Journal of Virology
|July 11, 1998
Summary
This study reconstitutes Sindbis virus RNA replication in vitro, finding that a protease-defective P123 polyprotein and nsP4 are essential for minus-strand RNA synthesis initiation. Polyprotein processing appears to inactivate this replication complex.
Area of Science:
- Virology
- Molecular Biology
- RNA Replication
Background:
- Sindbis virus (SIN) RNA replication initiation requires specific viral proteins.
- Understanding these early events is crucial for deciphering viral replication mechanisms.
Purpose of the Study:
- To reconstitute an in vitro system for template-dependent initiation of SIN RNA replication.
- To investigate the role of viral polyproteins and nsP4 in minus-strand RNA synthesis.
Main Methods:
- Utilized vaccinia virus recombinants to express SIN proteins in cell extracts.
- Assayed RNA replication activity using exogenous template RNAs.
- Employed protease-defective and cleavage-competent polyprotein mutants.
Main Results:
- Reconstituted in vitro system synthesized genome-length minus-sense RNA using protease-defective P123 and nsP4.
- Replicase activity was dependent on exogenous RNA and specific for alphavirus plus-strand templates.
- Polyprotein processing, particularly by nsP2 protease, inactivated the minus-strand initiation complex.
Conclusions:
- Provides evidence that processing of the Sindbis virus polyprotein inactivates the minus-strand RNA initiation complex.
- Establishes a functional assay for purifying the nsP4 RNA-dependent RNA polymerase.