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Expression of biologically active middle T antigen of polyoma virus from recombinant baculoviruses
J Forstová1, N Krauzewicz, B E Griffin
1Department of Virology, Royal Postgraduate Medical School, London, UK.
Abstract:
Two different recombinant baculoviruses have been generated for expressing the middle T antigen (MT) of polyoma virus in insect (Sf9) cells. One (pAcI-PyMT) produces moderate levels of MT and the other (pVL-PyMT) high levels. Indirect immunofluorescence and cellular fractionation studies with pAcI-PyMT infected Sf9 cells give results similar to those observed with wild type polyoma virus infected mouse cells, and show MT to be mainly associated with cytoplasmic membranes in the insect cell. In the latter, a sub-population of MT is phosphorylated in in vitro protein kinase assays. The yields of MT from pVL-PyMT infected cells are high enough to suggest that this protein can now be produced by this method in sufficient amounts for definitive biochemical and crystallographic analyses.
Insights
Researchers developed two baculoviruses to express polyoma virus middle T antigen (MT) in insect cells. High-yield expression using pVL-PyMT enables further biochemical and crystallographic studies of this important viral protein.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- Polyoma virus middle T antigen (MT) is a key viral protein implicated in cellular transformation.
- Efficient expression systems are needed for detailed analysis of MT structure and function.
Purpose of the Study:
- To generate recombinant baculoviruses for expressing polyoma virus middle T antigen (MT) in insect (Sf9) cells.
- To assess the expression levels and characteristics of MT produced in insect cells.
Main Methods:
- Generation of two recombinant baculoviruses (pAcI-PyMT and pVL-PyMT) for MT expression.
- Indirect immunofluorescence and cellular fractionation to localize MT.
- In vitro protein kinase assays to assess MT phosphorylation.
Main Results:
- Both baculoviruses expressed MT in Sf9 cells, with pVL-PyMT achieving high levels.
- MT was primarily localized to cytoplasmic membranes in insect cells, similar to mammalian cells.
- A sub-population of MT was phosphorylated in vitro.
Conclusions:
- Recombinant baculovirus expression, particularly with pVL-PyMT, provides a scalable method for producing polyoma virus middle T antigen.
- The insect cell expression system yields MT suitable for advanced biochemical and crystallographic analyses.
- MT localization and phosphorylation in insect cells mirror findings in mammalian systems, validating the model.