Figure 1.

Early rounds of HIV transcription. At the HIV LTR, TATA-binding protein (TBP) is recruited to the TATA box with the aid of Sp1. This interaction is subsequently stabilized by TFIIA and TFIIB. Preinitiation complex assembly is completed by the sequential addition of Pol II•TFIIF, TFIIE, and TFIIH and is followed by promoter clearance. Pol II quickly falls under the negative influence of DSIF and NELF, pausing after the generation of a short, nascent transcript. The recruitment of P-TEFb through NFκB or other factors overcomes this inhibition by phosphorylating DSIF and NELF, allowing for productive elongation and the generation of HIV Tat.