Isolation and Preliminary Characterization of a Recombinant TAT Protein from Human Immunodeficiency Virus.

HIV-l encodes several trans-activating regulatory proteins. One of these proteins, Tat trans activator of transcription, acts in trans to control viral gene expression. Tat interacts with the cis-acting element, TAR, which is located in the viral long terminal repeat LTR, and is essential for virus replication. Tat is reported to be an RNA-binding protein, binding to TAR RNA rather than to TAR DNA. Tat is composed of 86 amino acids, is a nuclear protein, and contains at least three distinct functional domains. These are a the amino-terminal end which might participate in Tats transactivation function, b the basic region of the protein 8 lysines and arginines, which may be involved in the binding of TAR RNA in addition to serving for nuclear localization, and c the cysteine-rich region between residues 22 and 37 which participates in Tat transactivation in addition to possible involvement in metal-linked dimer. Tat protein can be considered a promising target for antiviral drug design. The Tat protein has a pivotal role in the emergence of HIV from the latent state, and suggests that antagonists of Tat may be able to suppress viral replication in blatantly infected cells while at the same time allowing them to function normally.