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Myristylation of a duck hepatitis B virus envelope protein is essential for infectivity but not for virus assembly
1Department of Microbiology and Immunology, University of California Medical Center, San Francisco 94143.
Abstract:
In addition to the major surface (S) protein, the envelope of the duck hepatitis B virus (DHBV) contains a related presurface (preS) protein whose N-terminus bears a covalently attached myristate group. We have explored the functional significance of this modification by examining the replicative potential of a mutant viral genome whose myristylation signal has been inactivated. Following transfection into permissive hepatoma cells, the mutant expresses an unmyristylated preS protein of normal size, immunoreactivity and stability. Cytoplasmic cores containing viral DNA are synthesized, and Dane particles are assembled and exported into the medium. However, the mutant is noninfectious when inoculated into susceptible ducklings. We conclude that myristylation of preS proteins is essential for hepadnaviral infectivity but not for viral assembly; myristylation is most likely required for an early step of the life cycle involving the entry or uncoating of virus particles.
Insights
Myristylation of the duck hepatitis B virus (DHBV) presurface (preS) protein is essential for viral infectivity. This lipid modification is not required for viral assembly but likely facilitates early life cycle steps like entry or uncoating.
Area of Science:
- Virology
- Molecular Biology
- Hepatitis B Virus Research
Background:
- Duck hepatitis B virus (DHBV) possesses major surface (S) and presurface (preS) proteins.
- The DHBV preS protein N-terminus is modified with a myristate group, a covalent lipid attachment.
Purpose of the Study:
- To investigate the functional importance of myristylation for the DHBV preS protein.
- To determine the role of preS myristylation in viral replication and infectivity.
Main Methods:
- Creation and transfection of a DHBV mutant genome with an inactivated myristylation signal.
- Analysis of preS protein expression, stability, and viral particle assembly in hepatoma cells.
- Assessment of mutant viral infectivity in susceptible ducklings.
Main Results:
- The mutant DHBV expressed an unmyristylated preS protein of normal characteristics.
- Viral DNA-containing cores were synthesized, and Dane particles were assembled and secreted.
- The mutant DHBV was noninfectious when inoculated into ducklings.
Conclusions:
- Myristylation of the DHBV preS protein is crucial for hepadnaviral infectivity.
- This lipid modification is dispensable for viral assembly.
- Myristylation likely plays a role in early viral life cycle stages, such as virus entry or uncoating.