The matrix protein of human immunodeficiency virus type 1 is required for incorporation of viral envelope protein into mature virions

Abstract

Accumulating evidence suggests that the matrix (MA) protein of retroviruses plays a key role in virus assembly by directing the intracellular transport and membrane association of the Gag polyprotein. In this report, we show that the MA protein of human immunodeficiency virus type 1 is also critical for the incorporation of viral Env proteins into mature virions. Several deletions introduced in the MA domain (p17) of human immunodeficiency virus type 1 Gag polyprotein did not greatly affect the synthesis and processing of the Gag polyprotein or the formation of virions. Analysis of the viral proteins revealed normal levels of Gag and Pol proteins in these mutant virions, but the Env proteins, gpl20 and gp4l, were hardly detectable in the mutant virions. Our data suggest that an interaction between the viral Env protein and the MA domain of the Gag polyprotein is required for the selective incorporation of Env proteins during virus assembly. Such an interaction appears to be very sensitive to conformational changes in the MA domain, as five small deletions in two separate regions of p17 equally inhibited viral Env protein incorporation. Mutant viruses were not infectious in T cells. When mutant and wild-type DNAs were cotransfected into T cells, the replication of wild-type virus was also hindered. These results suggest that the incorporation of viral Env protein is a critical step for replication of retroviruses and can be a target for the design of antiviral strategies.

Efficient HIV-1 replication can occur in the absence of the viral matrix protein

“…In particular, phosphorylation of MA on a C-terminal tyrosine has been shown to be crucial for the nuclear import of the viral preintegration complex and for virus replication in MDM (Gallay et al, 1995a,b). However, others have reported conflicting results that indicate that neither the N-proximal basic cluster nor the C-terminal tyrosine of MA contribute selectively to HIV-1 replication in MDM (Freed et al, , 1997Fouchier et al, 1997) MA is essential for the incorporation of HIV-1 Env protein spikes into nascent viral particles (Yu et al, 1992b;Dorfman et al, 1994). Small alterations throughout the globular core of HIV-1 MA blocked the incorporation of autologous Env protein, but not that of amphotropic murine leukemia virus (A-MLV), a widely divergent oncoretrovirus Mammano et al, 1995).…”

Comparison of the NMR and X‐ray structures of the HIV‐1 matrix protein: Evidence for conformational changes during viral assembly

“…arrangement, termed maturation, wherein the CA molecules condense to form the conical core particle that encapsidates the RNA-NC ribonucleoprotein complex, and the matrix proteins form a shell that remains associated with the inner face of the viral membrane (Gelderblom, 1991;Hoglund et al, 1992;Marx et al, 1988). Genetic analyses indicate that the matrix shell helps to anchor the transmembrane envelope protein (TM, gp41) on the surface of the virion, because mutations in both MA (Dorfman et al, 1994;Freed & Martin, 1996;Yu et al, 1992) and the intraviral domain of TM , 1996Mammano et al, 1995; can produce envelope-deficient virions.…”

Package of NDV-Pseudotyped HIV-Luc Virus and Its Application in the Neutralization Assay for NDV Infection

“…Previous reports have shown that the interaction between the matrix protein and the cytoplasmic domain of envelope proteins was required for the incorporation of the envelope proteins into mature viral particles [33,34,47]. Indeed, we saw a lower infection efficiency with the NDV-pseudotyped HIV-Luc virus compared to the VSV-G pseudotyped HIV-Luc virus ( Figure 2C), which we associated with a less-optimal interaction between the HIV-1 matrix and the cytoplasmic domain of NDV envelope proteins.…”

“…Although the NDV-pseudotyped HIV-Luc viral particle was successfully produced, the infection efficiency was found to be over 34-fold lower than with the VSV-G-pseudotyped HIV-Luc virus (P,0.01) ( Figure 2C). We hypothesized that this may be due to the impact of the cytoplasmic domain of the envelope proteins [33,34]. To address this, four plasmids containing mutant HN or F were constructed ( Figure 1A (Figure 3).…”