Abstract
Human myxovirus resistance 2 (MX2/MXB) is an interferon-stimulated gene (ISG), and was recently identified as a late post-entry suppressor of human immunodeficiency virus type-1 (HIV-1) infection, inhibiting nuclear accumulation of viral cDNAs. Although the HIV-1 capsid (CA) protein is believed to be the viral determinant of MX2 mediated inhibition, the precise mechanism of anti-viral action remains unclear. The MX family of dynamin-like GTPases also includes MX1/MXA, a well-studied inhibitor of a range of RNA and DNA viruses including influenza A virus (FLUAV) and hepatitis B virus but not retroviruses. MX1 and MX2 are closely related, and share a similar domain architecture and structure. However, MX2 possesses an extended N-terminus that is essential for anti-viral function and confers anti-HIV-1 activity on MX1 (MX1(NMX2)). Higher order oligomerization is required for the anti-viral activity of MX1 against FLUAV, with current models proposing that MX1 forms ring structures that constrict around viral nucleoprotein complexes. Here, we performed structure-function studies to investigate the requirements for oligomerization of both MX2 and chimeric MX1(NMX2) for the inhibition of HIV-1 infection. The oligomerization state of mutated proteins with amino acid substitutions at multiple putative oligomerization interfaces was assessed using a combination of covalent cross-linking, and co-immunoprecipitation. We show that, while monomeric MX2 and MX1(NMX2) mutants are not anti-viral, higher order oligomerization does not appear to be required for full anti-viral activity of either protein. We propose that lower-order oligomerization of MX2 is sufficient for effective inhibition of HIV-1.
IMPORTANCE Interferon (IFN) plays an important role in the control of virus replication during acute infection in vivo. Recently, cultured cell experiments identified human myxovirus resistance 2 (MX2/MXB) as a key effector in the interferon mediated post-entry block to human immunodeficiency virus type-1 (HIV-1) infection. MX2 is a member of a family of large dynamin-like GTPases that includes MX1/MXA, a closely related interferon inducible inhibitor of several viruses including influenza A virus (FLUAV), but not HIV-1. MX GTPases form higher-order oligomeric structures, and the oligomerization of MX1 is required for inhibitory activity against many of its viral targets. Through structure-function studies, we report that monomeric mutants of MX2 do not inhibit HIV-1. However, in contrast to MX1, oligomerization beyond dimer assembly does not seem to be required for the anti-viral activity of MX2 implying that fundamental differences exist between the anti-viral mechanisms employed by these closely related proteins.
IMPORTANCE Interferon (IFN) plays an important role in the control of virus replication during acute infection in vivo. Recently, cultured cell experiments identified human myxovirus resistance 2 (MX2/MXB) as a key effector in the interferon mediated post-entry block to human immunodeficiency virus type-1 (HIV-1) infection. MX2 is a member of a family of large dynamin-like GTPases that includes MX1/MXA, a closely related interferon inducible inhibitor of several viruses including influenza A virus (FLUAV), but not HIV-1. MX GTPases form higher-order oligomeric structures, and the oligomerization of MX1 is required for inhibitory activity against many of its viral targets. Through structure-function studies, we report that monomeric mutants of MX2 do not inhibit HIV-1. However, in contrast to MX1, oligomerization beyond dimer assembly does not seem to be required for the anti-viral activity of MX2 implying that fundamental differences exist between the anti-viral mechanisms employed by these closely related proteins.
| Original language | English |
|---|---|
| Pages (from-to) | 22-32 |
| Number of pages | 11 |
| Journal | Journal of Virology |
| Volume | 90 |
| Issue number | 1 |
| Early online date | 7 Oct 2015 |
| DOIs | |
| Publication status | Published - Jan 2016 |
Keywords
- Amino Acid Substitution
- Cell Line
- DNA Mutational Analysis
- HIV-1/immunology
- Host-Pathogen Interactions
- Humans
- Immunity, Innate
- Models, Molecular
- Mutant Proteins/genetics
- Myxovirus Resistance Proteins/genetics
- Protein Conformation
- Protein Multimerization
- Virus Replication
