Human immunodeficiency virus Tat protein (Tat)

The **Human immunodeficiency virus Tat protein** (Tat) is a small, multifunctional viral protein encoded by the tat gene of HIV-1 (and HIV-2), and is essential for efficient transcription and replication of the viral genome[1][2][3]. Tat acts as a potent trans-activator, binding to the trans-activation response element (TAR) RNA at the 5′ end of all nascent viral transcripts, and recruits the host cell's positive transcription elongation factor b (**P-TEFb**, comprised of Cyclin T1 and CDK9), which phosphorylates RNA polymerase II to dramatically increase the processivity of viral transcription[2][3][4][6][8]. Structurally, Tat is intrinsically disordered, highly flexible, and consists of multiple functional domains, including an N-terminal acidic region, a cysteine-rich region (metal binding), a hydrophobic core, and a basic domain (arginine-rich, responsible for RNA binding, nuclear localization, and cell entry)[1][2][3][5]. Uniquely, Tat protein is secreted from infected cells, can be internalized by neighboring uninfected cells via a protein transduction domain, and acts both intracellularly as a transcription factor and extracellularly as a toxin, modulating host immune function, enhancing apoptosis, and contributing to HIV-associated comorbidities (such as neuropathology and immune suppression)[2][3]. Tat's essential role in HIV replication and pathogenesis, along with its interaction with a defined set of viral and host factors, makes it a validated but challenging therapeutic target for HIV infection[4][6][8]. **Note:** There are currently no FDA-approved drugs that specifically target the Tat protein, but several investigational candidates and structural inhibitor development efforts exist targeting Tat’s binding to TAR RNA or P-TEFb[4][6].

Other names

Trans-Activator of TranscriptionHIV-1 TatTat proteinHIV Tat

Inhibition of transactivation (blocking Tat binding to TAR RNA or P-TEFb), Disruption of Tat protein folding or trafficking, Antagonism of Tat-mediated transcriptional enhancement