Figure 4.

Possible mechanisms for maintaining latent viral genomes. The two panels represent two possible chromatin states over the HIV LTR in resting T cells in which the HIV genome is maintained in a silent state. In the upper panel, the entire LTR is covered in nucleosomes and initiation from the promoter is completely blocked. A less extreme but similar possibility (not pictured) is that accessibility of some factors is allowed, but initiation is still blocked. The lower panel depicts a state in which initiation is allowed, but all polymerases are left promoter proximally paused. HEXIM proteins may associate with TAR and act as a P-TEFb repressor.