Analogous to HIV-1 Tat, the cellular bromodomain-containing protein 4 (BRD4) recruits p-TEFb to cellular promoters to exert control at a transcription elongation step (Fig. 7A) (67), with Tat thought to compete with BRD4 for p-TEFb binding during HIV-1 infection (67, 68). Here, TAT is linked to HIV-1 infection.