Tat basic domain: A "Swiss army knife" of HIV-1 Tat?

Tat (transactivator of transcription) regulates transcription from the HIV provirus. It plays a crucial role in disease progression, supporting efficient replication of the viral genome. Tat also modulates many functions in the host genome via its interaction with chromatin and proteins. Many of the functions of Tat are associated with its basic domain rich in arginine and lysine residues. It is still unknown why the basic domain exhibits so many diverse functions. However, the highly charged basic domain, coupled with the overall structural flexibility of Tat protein itself, makes the basic domain a key player in binding to or associating with cellular and viral components. In addition, the basic domain undergoes diverse posttranslational modifications, which further expand and modulate its functions. Here, we review the current knowledge of Tat basic domain and its versatile role in the interaction between the virus and the host cell.