Identification of domains in the simian immunodeficiency virus matrix protein essential for assembly and envelope glycoprotein incorporation
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S A González1, A Burny, J L Affranchino
1Centro de Virología Animal, Buenos Aires, Argentina. sag@cevan.sld.ar
Abstract:
The matrix domain (MA) of the simian immunodeficiency virus (SIV) is encoded by the amino-terminal region of the Gag polyprotein precursor and is the component of the viral capsid that lines the inner surface of the virus envelope. To define domains of the SIV MA protein that are involved in virus morphogenesis, deletion and substitution mutations were introduced in this protein in the context of a gag-protease construct and expressed in the vaccinia virus vector system. The MA mutants were characterized with respect to synthesis and processing of the Gag precursor, assembly and release of virus-like particles, and incorporation of the envelope (Env) glycoprotein into particles. We have identified two regions of the SIV MA which are critical for particle formation. Both domains are located in a central hydrophobic alpha-helix of the SIV MA, according to data on the structure of this protein. In addition, we have characterized a domain whose mutation impairs the incorporation of SIV Env glycoproteins with long transmembrane cytoplasmic tails into particles. Interestingly, these mutant particles retained the ability to associate with SIV Env proteins with short cytoplasmic tails.
Insights
Researchers identified key regions in the simian immunodeficiency virus (SIV) matrix (MA) protein essential for virus particle formation. Mutations in these domains impact SIV assembly and envelope glycoprotein incorporation.
Area of Science:
- Virology
- Molecular Biology
- Structural Biology
Background:
- The matrix (MA) domain of simian immunodeficiency virus (SIV) Gag polyprotein precursor forms the viral capsid inner lining.
- Understanding MA's role is crucial for defining SIV morphogenesis and potential therapeutic targets.
Purpose of the Study:
- To identify specific domains within the SIV MA protein critical for virus particle formation.
- To investigate the impact of mutations in these domains on Gag processing, virus-like particle assembly, and envelope glycoprotein incorporation.
Main Methods:
- Introduction of deletion and substitution mutations into the SIV MA protein.
- Expression of mutated gag-protease constructs using the vaccinia virus vector system.
- Characterization of MA mutants focusing on Gag precursor processing, particle assembly, release, and Env glycoprotein incorporation.
Main Results:
- Two critical regions within the SIV MA protein essential for particle formation were identified.
- These critical domains are located in a central hydrophobic alpha-helix of the MA protein.
- A specific domain was characterized whose mutation hinders the incorporation of SIV Env glycoproteins with long cytoplasmic tails, while retaining association with Env proteins with short tails.
Conclusions:
- Specific domains within the SIV MA protein are indispensable for viral morphogenesis.
- The central hydrophobic alpha-helix of SIV MA harbors key regions for particle formation.
- SIV MA plays a role in the selective incorporation of envelope glycoproteins based on their cytoplasmic tail length.