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Human immunodeficiency virus type 1 MA deletion mutants expressed in baculovirus-infected cells: cis and trans
1Laboratoire de Virologie et Pathogénèse Moléculaires, CNRS URA-1487, Faculté de Médecine, Montpellier, France.
Abstract:
The role of the matrix protein (MA) of human immunodeficiency virus type 1 in intracellular transport, assembly, and extracellular release of Gag polyprotein precursor (Pr55gag) was investigated by deletion mutagenesis of the MA domain of recombinant Gag precursor expressed in baculovirus-infected cells. In addition, three carboxy-terminally truncated forms of the Gag precursor, representing mainly the MA, were constructed. One corresponded to an MA with a deletion of its last 12 residues (amb120), while the others corresponded to the entire MA with an additional sequence from the N-terminal portion of the CA (amb143 and och180). Deletions within the MA central region (residues 41 to 78) appeared to be detrimental to Gag particle assembly and budding from the plasma membrane. A slightly narrower domain, between amino acids 41 and 68, was found to be critical for soluble Gag secretion. Mutations which totally or partially deleted one or the other of the two polybasic signals altered the transport of N-myristylated Gag precursor to the plasma membrane. In coexpression with wild-type Gag precursor, a discrete trans-dominant negative effect on wild-type Gag particle assembly and release was observed with deletion mutants located in the central MA region (residues 41 to 78). A more significant negative effect was obtained with the two recombinant proteins of amb120 and och180, which redirected the Gag particle assembly pathway from the plasma membrane compartment to intracellular vesicles (amb120) and to the nuclear compartment (och180).
Insights
The matrix protein (MA) of human immunodeficiency virus type 1 is crucial for Gag polyprotein precursor (Pr55gag) transport, assembly, and release. Specific MA deletions disrupt these processes, affecting viral particle formation and release pathways.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- The matrix protein (MA) of human immunodeficiency virus type 1 (HIV-1) plays a key role in the virus life cycle.
- Understanding MA's function is vital for developing antiviral strategies.
Purpose of the Study:
- To investigate the role of the MA domain in HIV-1 Gag polyprotein precursor (Pr55gag) intracellular transport, assembly, and release.
- To identify critical regions within MA responsible for these processes.
Main Methods:
- Deletion mutagenesis of the MA domain in recombinant Gag precursor expressed in baculovirus-infected cells.
- Construction and analysis of carboxy-terminally truncated Gag forms.
- Coexpression studies with wild-type Gag precursor.
Main Results:
- Deletions in the MA central region (residues 41-78) impaired Gag particle assembly and budding.
- A narrower domain (residues 41-68) was critical for soluble Gag secretion.
- Mutations affecting polybasic signals altered Gag precursor transport to the plasma membrane.
- Specific MA deletion mutants exhibited dominant-negative effects on wild-type Gag assembly and release, redirecting pathways to intracellular vesicles or the nucleus.
Conclusions:
- The MA domain is essential for proper intracellular transport, assembly, and release of HIV-1 Gag.
- Specific regions and signals within MA dictate Gag localization and virion production.
- MA deletion mutants can interfere with wild-type virus assembly and release, offering insights into viral pathogenesis.