www.landesbioscience.com Communicative & Integrative Biology e25145-1 Communicative & Integrative Biology 6:5, e25145; September/October 2013; © 2013 Landes Bioscience

The human immunodeficiency virus type I (HIV-1) encodes three structural (gag, pol and env), four accessory (vif, vpr, vpu and nef) and two regulatory (tat and rev) genes, the products of which are responsible for establishing sophisticated interactions between the virus and human host. HIV-1 transcriptional activa-tor (Tat) is a small (~11 kDa) basic protein that binds to the trans-activation-response element (TAR) on the nascent viral RNA and recruits molecular components for efficient transcriptional elongation.1 Thus, Tat displays an array of functions that are essential for viral gene expression and replication, but also affects host gene expression.2 Tat is an early regulatory protein that has a variable length of 86–103 aa (depending on viral isolates) and is encoded by two exons. The first exon encodes the first 72 amino acids and the second exon encodes for the remaining residues. Tat is actively released by infected T-cells into the extracellula