The human immunodeficiency virus (HIV) transactivator Tat is a potent activator of
transcription from the HIV long terminal repeat and is essential for efficient viral gene
expression and replication. Tat has been shown to interact with components of the basal
transcription machinery and transcriptional activators. Here we identify the cellular
coactivator PC4 as a Tat-interacting protein using the yeast two-hybrid system and
confirmed this interaction both in vitro and in vivo by coimmunoprecipitation. We found that …