Definition of the RRE binding and activation domains of the caprine arthritis encephalitis virus Rev protein

Caprine arthritis encephalitis virus (CAEV) is a lentivirus which is closely related by nucleotide sequence and biological properties to visna virus and is more distantly related to the human AIDS virus, HIV-1. Previous studies indicated that the CAEV Rev protein (Rev-C) functions as a trans-activator of mRNA cytoplasmic transport and expression. The function of Rev-C is mediated through an RNA element (RRE-C) present between nucleotides (nt) 7906 and 8110 in the CAEV env gene. In this study, RNA/protein immunoprecipitation experiments were used to demonstrate that Rev-C binds directly to the 204-nt RRE-C in vitro. Competition assays illustrate that this interaction is specific for the positive sense RRE-C RNA. Glutaraldehyde crosslinking studies demonstrate that the wildtype Rev-C protein can also form multimeric complexes in vitro. Deletions or amino acid alterations within the basic domain of Rev-C reduce affinity for the RRE and disrupt assembly of Rev-C multimers in vitro, indicating that this domain is involved in RRE binding and Rev multimer formation. Mutations within the leucine-rich domain of Rev-C do not greatly effect RRE-C binding or self-assembly. However, previous results demonstrate that some leucine-rich domain mutants are unable to trans-activate. These data are consistent with the hypothesis that the leucine domain is the effector domain of Rev-C.