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Transcript initiation and 5'-end modifications are separable events during vesicular stomatitis virus transcription
1Department of Microbiology and Immunology, University of Tennessee-Memphis, Memphis, Tennessee 38163, USA.
Journal of Virology
|August 10, 1999
Summary
This study developed a novel vesicular stomatitis virus (VSV) system to investigate transcription start sequences and mRNA modifications. Mutations in the start sequence revealed that 5'-end capping and methylation are separable from transcript initiation, impacting RNA stability.
Area of Science:
- Virology
- Molecular Biology
- RNA Virus Replication
Background:
- Vesicular stomatitis virus (VSV) is a non-segmented negative-strand RNA virus crucial for studying viral transcription.
- Understanding the regulation of viral gene expression, including transcript initiation and mRNA modification, is essential for controlling viral infections.
Purpose of the Study:
- To investigate the impact of mutations in the transcription start sequence on VSV transcript initiation and 5'-mRNA modifications.
- To establish a novel bipartite VSV replication system for studying these effects.
Main Methods:
- Development of a bipartite VSV replication system using two genomic RNAs (VSVDeltaG and GFC).
- Introduction of mutations into the transcription start sequence of the CAT gene within the GFC component.
- Analysis of CAT transcript synthesis, accumulation, polyadenylation, and 5'-end modification (capping and methylation) in vivo and in vitro.
Main Results:
- Mutations in the VSV transcription start sequence significantly reduced CAT transcript levels in vivo.
- In vitro transcription assays showed that mutations did not prevent initiation but led to unstable, truncated transcripts lacking poly(A) tails.
- Truncated transcripts failed to undergo proper 5'-end capping and methylation, indicating these events are separable from initiation.
Conclusions:
- Transcript initiation and 5'-end mRNA modification (capping/methylation) are distinct, separable events during VSV transcription.
- A model is proposed linking VSV polymerase processivity to proper 5'-end modification, suggesting a proofreading mechanism for defective transcripts.