Identification of a viral gene encoding a ubiquitin-like protein

Area of Science:

• Molecular Virology
• Insect Pathology
• Biochemistry

Background:

• Baculoviruses, such as AcMNPV, are DNA viruses used extensively for protein expression in insect cells.
• AcMNPV encodes a protein, v-ubi, with significant homology to eukaryotic ubiquitin.
• Understanding viral gene regulation is crucial for optimizing baculovirus expression systems.

Purpose of the Study:

• To characterize the temporal expression of the AcMNPV v-ubi gene.
• To investigate the function and regulation of the viral ubiquitin-like protein.
• To develop a tool for monitoring baculovirus gene expression during infection.

Main Methods:

• Construction of a recombinant baculovirus (AcUbi-beta Gal) expressing a ubiquitin-beta-galactosidase fusion protein.
• Temporal analysis of fusion protein expression post-infection using Western blotting and enzyme assays.
• Transcriptional mapping and Southern blot analysis to confirm gene locus and expression patterns.

Main Results:

• The v-ubi gene is transcribed during the late phase of AcMNPV infection, with expression peaking at 14-18 hours post-infection.
• The ubiquitin-beta-galactosidase fusion protein accumulated to significant levels, demonstrating the efficacy of the v-ubi promoter.
• Recombinant viral sequences remained stable, and normal viral ubiquitin message was produced.
• The host cell polyubiquitin gene sequence was determined and found to be identical to animal ubiquitin.

Conclusions:

• The v-ubi gene is a bona fide late gene in the AcMNPV life cycle.
• The AcUbi-beta Gal system provides a reliable method for studying baculovirus gene expression dynamics.
• The viral ubiquitin-like protein shares high identity with host and animal ubiquitin, suggesting potential functional roles in viral pathogenesis or host interaction.