Tryptophan 95, an Amino Acid Residue of the Caprine Arthritis Encephalitis Virus Vif Protein Which Is Essential for Virus Replication

Abstract

The Caprine arthritis encephalitis virus (CAEV) vif gene was demonstrated to be essential for efficient virus replication. CAEV Vif deletion mutants demonstrated an attenuated replication phenotype in primary goat cell cultures and resulted in abortive infection when inoculated into goats. In this study, we determined the in vitro replication phenotype of five CAEV Vif point mutant infectious molecular clones and the ability of the corresponding in vitro translated Vif proteins to interact with the CAEV Pr55(gag) in the glutathione S--transferase (GST) binding assay. Here we show that (i) three of the mutants (S170E, S170G, S197G) behaved as the wild-type CAEV according to virus replication and Vif--Gag interactions; (ii) one mutant (Vif 6mut) was replication incompetent and bound weakly to GST-Gag fusion proteins; and (iii) one mutant (Vif RG) was impaired for replication while retaining its interaction properties. This mutant points out the critical importance of the CAEV Vif tryptophan residue at position 95 for efficient virus replication, defining for this lentivirus a functional domain unrelated to the Gag binding region.

Simultaneous Mutations in CA and Vif of Maedi-Visna Virus Cause Attenuated Replication in Macrophages and Reduced Infectivity In Vivo

“…The mutation in the vif gene is a P-to-S mutation in the C terminus, where membrane association, Gag interaction, and Vif multimerization have been mapped for HIV-1; interaction with Gag has also been mapped for caprine arthritis encephalitis virus (3,9,10,25,37). The interaction with Gag has been mapped to the nucleocapsid part of Gag in vitro, but no interaction has been detected with CA (3,25).…”

“…The interaction with Gag has been mapped to the nucleocapsid part of Gag in vitro, but no interaction has been detected with CA (3,25). However, Vif has been shown to play a role in the stability of the core of HIV-1 (23), and the interaction between Vif and CA may either be indirect or too transient to be detected by standard methods that are used for detecting protein-protein interactions.…”

Fully functional, naturally occurring and C-terminally truncated variant human immunodeficiency virus (HIV) Vif does not bind to HIV Gag but influences intermediate filament structure

“…Thus, it is conceivable that, also in the case of Vif from strain NDK, which was employed in the previously described in vitro binding assays (Bouyac et al , 1997 ) and is also shown here to bind strongly to GST–Gag, deletion of the C terminus does not actually remove the Gag-binding domain of Vif but rather leads to the generation of an inactive Vif protein (strain NDK) that has lost both Gag-binding activity and function. It is of note in this context that in the caprine arthritis–encephalitis virus (CAEV) model system, binding of CAEV-Vif to CAEV-Gag does not correlate with CAEV-Vif function (Seroude et al , 2001 ) and is independent of the presence of 24 C-terminal amino acids of Vif (M. Suzan & G. Audoly, unpublished results).…”