A triple-arginine motif in the amino-terminal domain and oligomerization are required for HIV-1 inhibition by human MX2.
Bottom Line: First, we describe an essential triple-arginine motif in the amino-terminal domain.Second, we demonstrate that this 91-residue domain mediates antiviral activity when appended to heterologous proteins, and we provide genetic evidence that protein oligomerization is required for MX2 function.These insights will facilitate future work aiming to elucidate MX2's mechanism of action.
Affiliation: Department of Infectious Diseases, King's College London, London, United Kingdom firstname.lastname@example.org email@example.com.Show MeSH
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Mentions: Given that transfer of the amino-terminal 91 amino acids of MX2 onto MX1 bestows full anti-HIV-1 function (13), we wished to determine whether this domain would still have this capability when appended to an entirely unrelated protein. We initially chose to use mouse Fv1b as the substrate since this protein is an inhibitor of retrovirus infection (N-tropic NLV but not HIV-1) (20, 21), suppression is manifested as a lack of viral cDNA integration (22, 23), and it is naturally oligomeric (24). Remarkably, fusing residues 1 to 91 of MX2 to the amino terminus of Fv1b (NMX2-Fv1b) conferred potent HIV-1-inhibitory activity, whereas the parental Fv1b protein had no effect (Fig. 4A). Importantly, a genetic constraint of MX2 function was faithfully preserved, as introduction of the RRR11–13A mutation into this chimeric protein abrogated activity. As a confirmation of Fv1b functionality, both fusion proteins suppressed N-MLV (but not B-tropic MLV) infection as efficiently as the wild-type protein (Fig. 4B). Therefore, the amino-terminal domain of human MX2 is the only element of MX1/MX2 that is necessary for HIV-1 inhibition in the context of a heterologous fusion partner.
Affiliation: Department of Infectious Diseases, King's College London, London, United Kingdom firstname.lastname@example.org email@example.com.