Borf-1 protein identified as a transcriptional trans-activator of bovine foamy virus

Bovine foamy virus (BFV), a member of the spumavirus subfamily of retroviruses,contains two open reading frames (ORF-1 and ORF-2) in addition to the genes coding for gag,po/and env. Borf-1 protein, encoded by BFV ORF-1, is identified as a transcriptional transactivator, which augments gene expression directed by the viral long terminal repeat (LTR).Further investigations in transient expression assays reveal that the Borf-1 responsive elements are located in the U3 domain of the LTR, upstream from position -140 ( + 1 represents the transcription initiation site), and the BFV RU5 region has an inhibitory effect in LTR-directed gene expression.