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Evidence that developmentally regulated control of gene expression by a parvoviral allotropic determinant is particle
1Department of Human Genetics, Yale University School of Medicine, New Haven, Connecticut 06510.
Abstract:
An infectious molecular clone of the immunosuppressive strain of the autonomous parvovirus minute virus of mice [MVM(i)] was constructed deriving left-hand terminal sequences from a rare encapsidated plus strand. Progeny virus was shown to package the same proportions of plus and minus strands as did authentic MVM(i) virions. Rescue of virus from this clone also resulted in the repair of a 21-base truncation at the junction between the right-hand end of the viral insert and the vector and generated the same heterogeneous 5' end as is present in standard MVM(i) DNA. Progeny virus rescued by transfection of this clone into mouse cell lines displayed the lymphotropic phenotype characteristic of the parental MVM(i) virus from which it was derived. However, analysis of viral RNA from transfected mouse fibroblasts revealed that the MVM(i) and MVM(p) genomic clones are transcribed at the same low level. Furthermore, transfected fibroblasts yielded similar numbers of infectious centers regardless of which MVM clone was introduced. These results contrast markedly with the different infectivities of MVM(i) and MVM(p) particles and with the observation that viral transcription in fibroblasts productively infected with MVM(p) virions is 100-fold greater than that seen in the restrictive MVM(i) particle-mediated infection. These results suggest that the developmentally regulated intracellular factors controlling host cell susceptibility at the level of viral transcription interact with a component of the incoming viral capsid, rather than with a sequence within the viral DNA.
Insights
Researchers created a molecular clone of minute virus of mice [MVM(i)] to study its immunosuppressive properties. Viral transcription levels and infectivity in mouse cells suggest capsid proteins, not DNA sequences, dictate host cell susceptibility.
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- Minute virus of mice (MVM) is an autonomous parvovirus with distinct strains, including the immunosuppressive MVM(i) and the more infectious MVM(p).
- Understanding the molecular basis of MVM strain-specific tropism and infectivity is crucial for deciphering parvovirus-host interactions.
Purpose of the Study:
- To construct an infectious molecular clone of the MVM(i) strain.
- To investigate the role of viral DNA and capsid components in determining host cell susceptibility and viral transcription levels.
Main Methods:
- Construction of a full-length infectious molecular clone of MVM(i) using specific terminal sequences.
- Transfection of mouse cell lines with the MVM(i) clone and analysis of viral progeny.
- Quantification of viral RNA transcription and infectious center formation.
- Comparison of MVM(i) and MVM(p) transcription and infectivity.
Main Results:
- The MVM(i) molecular clone produced infectious virus packaging similar plus/minus strand proportions as authentic virions.
- Transfected cells exhibited the characteristic lymphotropic phenotype of MVM(i), but viral transcription levels were low and similar to MVM(p) clones.
- Infectious center formation was comparable for both MVM(i) and MVM(p) clones, contrasting with the differential infectivity of their respective virions.
Conclusions:
- Host cell susceptibility to MVM, particularly at the level of viral transcription, is influenced by developmentally regulated intracellular factors.
- These factors appear to interact with components of the incoming viral capsid, rather than specific DNA sequences, to modulate transcription and infectivity.
- The study highlights the importance of the viral capsid in determining the outcome of parvovirus infection in a host-specific manner.