A cDNA for a Protein That Interacts with the Human Immunodeficiency Virus Tat Transactivator

The human immunodeficiency virus (H1V) tat protein (Tat) is a positive regulator of virus gene expression and replication. Biotinylated Tat was used as a probe to screen a λgtll fusion protein library, and a complementary DNA encoding a protein that interacts with Tat was cloned. Expression of this protein, designated TBP-1 (for Tat binding protein-l), was observed in a variety of cell lines, with expression being highest in human cells. TBP-1 was localized predominantly in the nucleus, which is consistent with the nuclear localization of Tat. In cotransfection experiments, expression of TBP-1 was able to specifically suppress Tat-mediated transactivation. The strategy described may be useful for direct identification and cloning of genes encoding proteins that associate with other proteins to modulate their activity in a positive or negative fashion.