TAT MEDIATES TRANSCRIPTIONAL ACTIVATION OF HIV-1 GENE IN-VITRO

Gene expression of human immunodeficiency virus (HIV-1) is greatly enh anced by a viral transactivator, the Tat protein, which interacts with R region sequences' of the HIV-1 long terminal repeat (LTR). There is no direct evidence to indicate transcriptional activation of HIV-1 by Tat. Using an in vitro transcription system, we demonstrate that an e stablished mouse cell line, which constitutively expresses Tat protein , selectively stimulates the steady state levels of the transcripts di rected from the Long terminal repeat (LTR) sequences of HIV-1. The gel binding retardation assays further demonstrate a stable activated com plex, formed due to direct binding of Tat to DNA elements of the HIV-1 LTR. These data implicate transcription as the site of Tat action in trans-activation and could play an essential role in human immunodefic iency virus replication, similar to the nuclear trans-activators of ot her viruses.