The Rev protein of visna virus is localized to the nucleus of infected cells

Visna virus is a lentivirus of sheep that is distantly related to the human lentivirus HIV-1. Like other lentiviruses, the genome of visna virus contains multiple small open reading frames that encode viral regulatory proteins. The product of one of these regulatory genes is the visna virus Rev protein, Rev-V. In this report, immunoprecipitation of visna virus-infected cells using a specific anti-Rev-V antibody, generated to a synthetic, carboxyl-terminal peptide of Rev-V, brings down a 22.5-kDa protein identical in size to the protein expressed from a functional Rev-V cDNA clone. Examination of the phosphorylation state of Rev-V indicates that it, unlike the Rev proteins of HIV-1 and CAEV, is not efficiently phosphorylated in infected cells. Cell fractionation and immunofluorescence analysis indicate that, in contrast to a previous report, Rev-V is strongly localized to the nucleus and concentrated in nucleoli of visna virus-infected cells. In addition, Rev-V localizes similarly in several different primary cells, in particular macrophages, infected with visna virus. These data indicate that the Rev-V protein is produced during visna virus infection and is localized to the nucleolus of the infected cell.