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Polyomavirus genome and polyomavirus enhancer-driven gene expression during myogenesis
1Dipartimento di Biopatologia Umana, Università di Roma La Sapienza, Italy.
Abstract:
The mRNAs for myogenic functions are coordinately transcribed with polyomavirus (Py) early mRNA during in vitro differentiation of mouse C2 myoblast cells. Sequence analysis shows that the A domain of the Py enhancer includes an E1A-like consensus sequence that is also found in the 5' upstream region of two genes expressed during myoblast differentiation: alpha-actin and myosin light chain. Therefore, the coordinate expression of such genes with Py early mRNA may be activated by a common cellular regulatory factor. In the present work, we report that C2 cells surviving Py infection are unable to differentiate and do not express alpha-actin and myosin light-chain mRNAs. Hybrids between such Py-resistant myoblast cells and the parental cells exhibited dominance of the permissibility to Py growth and of the expression of myogenic mRNAs. In C2 cells transiently transfected with a chimeric plasmid (pSVPy12CAT) harboring the bacterial chloramphenicol acetyltransferase (CAT) gene driven by the Py enhancer-promoter region, the CAT gene was expressed irrespective of their stage of differentiation. Moreover, undifferentiated stably transfected cells expressing the CAT gene restricted viral growth. Py-resistant C2 myoblasts transiently transfected with pSVPy12CAT also expressed the CAT gene driven by the Py enhancer. This contradictory finding is similar to results previously obtained by other investigators with cloned genes specific for myogenic functions, and it may be explained by a structural difference between the pSVPy12CAT and the Py genomic organizations in which the viral enhancer operates.
Insights
Polyomavirus (Py) infection prevents mouse C2 myoblast differentiation and myogenic gene expression. However, viral enhancer activity in transfected cells suggests complex regulatory interactions influencing gene expression during myogenesis.
Area of Science:
- Molecular Biology
- Cell Biology
- Virology
Background:
- Myogenic differentiation involves coordinated gene expression.
- Polyomavirus (Py) early mRNA is co-transcribed with myogenic function mRNAs.
- A common regulatory factor may control coordinate gene expression.
Purpose of the Study:
- Investigate the relationship between Py infection and myoblast differentiation.
- Identify regulatory mechanisms of coordinate gene expression.
- Examine the role of the Py enhancer in myogenic gene expression.
Main Methods:
- In vitro differentiation of mouse C2 myoblasts.
- Polyomavirus infection and resistance studies.
- Analysis of alpha-actin and myosin light-chain mRNA expression.
- Transfection with chimeric plasmids (pSVPy12CAT) for gene expression analysis.
Main Results:
- Py infection inhibits C2 myoblast differentiation and myogenic mRNA expression.
- Py-resistant myoblasts show dominant permissibility to Py growth and myogenic mRNA expression in hybrids.
- The Py enhancer-driven CAT gene is expressed in transfected C2 cells regardless of differentiation stage.
- Undifferentiated cells expressing the CAT gene restricted viral growth, while Py-resistant cells also expressed the CAT gene.
Conclusions:
- Py infection disrupts normal myoblast differentiation and gene expression.
- Viral and cellular regulatory factors interact during myogenesis.
- The Py enhancer's function may differ in transient transfections versus genomic integration.