Trans-activation_response_element_(TAR)
The HIV trans-activation response (TAR) element is an RNA element which is known to be required for the trans-activation of the viral promoter and for virus replication. The TAR hairpin is a dynamic structure[1] that acts as a binding site for the Tat protein, and this interaction stimulates the activity of the long terminal repeat promoter.[2]
Further analysis has shown that TAR is a pre-microRNA that produces mature microRNAs from both strands of the TAR stem-loop.[3] These miRNAs are thought to prevent infected cells from undergoing apoptosis by downregulating the genes ERCC1, IER3,[4] CDK9, and Bim.[5]
Human polyomavirus 2 (JC virus) contains a TAR-homologous sequence in its late promoter[6] that is responsive to HIV-1 derived Tat.[7][8]