Expression of simian virus 40 T antigen in insect cells using a baculovirus expression vector

Area of Science:

• Molecular Biology
• Virology
• Biochemistry

Background:

• Simian virus 40 (SV40) is a well-studied polyomavirus with significant roles in cell cycle regulation and cancer research.
• SV40 large T antigen (T-ag) is a multifunctional protein crucial for viral replication and cellular transformation.
• Efficient production of functional T-ag is essential for various biochemical and biological studies.

Purpose of the Study:

• To investigate the synthesis and functional characterization of SV40 large T and small t antigens in insect cells.
• To evaluate the efficacy of the baculovirus expression system for producing SV40 T-ag.
• To compare the biochemical activities of insect cell-derived T-ag with T-ag produced in mammalian systems.

Main Methods:

• Construction of recombinant baculoviruses containing either the genomic or cDNA copy of the SV40 early region.
• Expression of SV40 large T and small t antigens in Spodoptera frugiperda (Sf9) insect cells.
• Biochemical characterization of insect cell-derived T-ag, including post-translational modifications and functional assays (DNA binding, ATPase, helicase activity).

Main Results:

• Recombinant baculoviruses expressing SV40 early genes produced both small t and large T antigens in insect cells.
• A cDNA-based construct led to significantly higher levels of large T antigen synthesis compared to a genomic construct.
• Insect cells performed post-translational modifications on T-ag, including phosphorylation, palmitylation, glycosylation, and oligomerization.
• SV40 T-ag produced in insect cells exhibited comparable origin-specific DNA binding, ATPase, and helicase activities to mammalian-derived T-ag.

Conclusions:

• The baculovirus expression system is a viable and efficient method for producing functional Simian virus 40 large T antigen in insect cells.
• Insect cell-derived T-ag possesses biochemical activities comparable to its mammalian counterpart, validating its utility in research.
• This system facilitates the large-scale production of T-ag, supporting future investigations requiring substantial quantities of the protein.