Tat, a regulatory protein in HIV, plays a pivotal role in the virus's life cycle and immunopathogenesis. Its primary function is to transactivate HIV genome transcription, overcoming obstacles to elongation by binding to the TAR sequence on nascent viral RNA. Additionally, Tat may stimulate reverse transcription at low concentrations but inhibit it at high amounts. Beyond transcriptional control, Tat can activate infected T cells, promoting viral replication even before integration, and can be released extracellularly, targeting immune cells and facilitating viral spread. Extracellular Tat can also enter infected cells, reactivating latent reservoirs and promoting viral expression. Tat exists in two forms, one-exon and two-exon, with distinct functional properties. While both forms activate HIV-1 gene expression, the two-exon form also mediates immune hyperactivation, suggesting differential roles in later infection phases. Tat's multiple domains enable interaction with various receptors, contributing to its diverse functions in HIV pathogenesis.

HIV, Lymphocytes, Signaling, Immune System, Antigen