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The short Sendai virus leader region controls induction of programmed cell death
D Garcin1, G Taylor, K Tanebayashi
1Department of Genetics and Microbiology, University of Geneva School of Medicine, CMU, Switzerland.
Abstract:
The replication of nonsegmented minus-strand RNA genomes, like that of Sendai paramyxovirus (SeV), are controlled by the short leader regions present at each end of the linear genomes and antigenomes; the left and right promoters (PL and PR), respectively. Wild-type SeV is highly cytopathic in cell culture, because it induces programmed cell death (PCD). We have found that a recombinant SeV (rSeVGP42), in which the first 42 nt of le+ sequences at PL were replaced with the equivalent sequences of PR, and which produces infectious virus in amounts comparable to wild type, does not kill cells. Further, the increasing replacement of the terminal le+ sequences at PL with le- sequences led to a decreasing fraction of infected cells being apoptotic. This property (PCD-), moreover, is dominant in cells co-infected with SeVwt and rSeVGP42, and the mutant virus therefore appears to have gained a function which prevents PCD induced by SeVwt. Even though this virus has not been selected for naturally, it excludes SeVwt during co-infections of cultured cells or embryonated chicken eggs. The noncytopathic nature of cells infected or co-infected with rSeVGP42 leads automatically to stable, persistent infections. The mutation in rSeVGP42 is not in the protein coding regions of the viral genome, but in the 55-nt-long leader region which controls antigenome synthesis from genome templates. The SeV leader regions, which are expressed as short RNAs, thus appear to control the induction of PCD.
Insights
A modified Sendai virus (SeV) with altered leader sequences prevents programmed cell death (PCD) in infected cells. This noncytopathic virus excludes wild-type SeV and establishes persistent infections, highlighting the role of leader regions in PCD induction.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Nonsegmented minus-strand RNA viruses, such as Sendai virus (SeV), rely on leader sequences for replication control.
- Wild-type SeV is cytopathic, inducing programmed cell death (PCD) in host cells.
- Viral leader regions are short RNA sequences crucial for genome and antigenome synthesis.
Purpose of the Study:
- To investigate the role of SeV leader sequences in controlling viral replication and cytopathicity.
- To determine if modifying leader sequences can attenuate SeV-induced PCD.
- To assess the competitive fitness and persistence of modified SeV strains.
Main Methods:
- Construction of a recombinant SeV (rSeVGP42) with altered leader sequences at the left promoter (PL).
- Assessment of viral replication and infectious virus production in cell culture.
- Evaluation of apoptosis induction in cells infected with wild-type SeV and recombinant SeV strains.
- Co-infection experiments to determine the dominance of the noncytopathic phenotype.
Main Results:
- rSeVGP42, with modified leader sequences, replicates comparably to wild-type SeV but does not induce significant cell death.
- A dose-dependent decrease in apoptosis was observed with increasing replacement of leader sequences.
- The noncytopathic phenotype of rSeVGP42 is dominant, suppressing PCD induced by wild-type SeV during co-infection.
- rSeVGP42 excludes wild-type SeV in co-infected cells and embryonated eggs, leading to stable, persistent infections.
Conclusions:
- SeV leader regions, expressed as short RNAs, play a critical role in controlling PCD induction.
- Modification of leader sequences can attenuate SeV virulence, generating noncytopathic viruses.
- The noncytopathic SeV mutant exhibits enhanced fitness in co-infection models, outcompeting the wild-type virus.
- These findings offer insights into viral pathogenesis and the development of potentially safer viral vectors.