Structure of the HIV-1 promoter. The integrated HIV-1 genome is 9719 nucleotides in length. It includes two copies of the LTR which consist of a U3, R and U5 region, shown in the bottom panel. The genome encodes 9 genes which are shown in the top panel. The 5’LTR serves as the promoter for HIV-1 and is divided into the modulatory, enhancer, core promoter and TAR regions (shown enlarged in the middle panel). The binding sites for some of the ~50 TFs known to interact with the HIV-1 promoter are shown by colored ovals. The TATA box is shown by the grey rectangle, which serves as the binding site for the TATA binding protein (TBP) as part of the general transcription factor TFIID, to allow formation of the pre-initiation complex, just before the transcription start site (TSS), marked by the black arrow. The positions of the three nucleosomes, (Nuc-0, -1, and -2) on the HIV-1 5’LTR are marked by the grey shaded ovals. The DNase hypersensitivity regions (DHS-1 and -2) are the nucleosome-free regions on the promoter.