DELINEATING MINIMAL PROTEIN DOMAINS AND PROMOTER ELEMENTS FOR TRANSCRIPTIONAL ACTIVATION BY LENTIVIRUS TAT PROTEINS

Lentivirus Tat proteins comprise a novel class of RNA-binding transcri ptional activators that are essential for viral replication. In this s tudy, we performed a series of protein fusion experiments to delineate the minimal protein domains and promoter elements required for Tat ac tion. We show that a 15-amino-acid region of equine infectious anemia virus (EIAV) Tat protein, when fused to the GAIA or LexA DNA binding d omain, can activate transcription in appropriate promoter contexts. In the natural human immunodeficiency virus type 1 long terminal repeat, activation by Tat is dependent an multiple binding sites for the cell ular transcription factor SP1. We delineate a 114-amino-acid region of the SP1 glutamine-rich activation domain that when fused to the GALA DNA binding domain can support transcription activation by Tat. Using these Tat and SP1 derivatives, we show that Tat activation can be reco nstructed on a completely synthetic promoter lacking all cis-acting el ements unique to the human immunodeficiency virus long terminal repeat . Our results indicate that lentivirus Tat proteins have essential pro perties of typical cellular transcriptional activators and define usef ul reagents for studying the detailed mechanism of Tat action.