Fig. 6.

The PID of BRD4 inhibits the binding of Tat to P-TEFb. Biotinylated Tat was incubated with recombinant P-TEFb in the presence of BRD4 peptides corresponding to either amino acids 1209–1362 or 1209–1328 obtained after in vitro transcription/translation. Biotinylated Tat and associated factors were pulled down by streptavidin/agarose followed by Western blotting with an antiserum specific for CDK9 or streptavidin/horseradish peroxidase (SA-HRP) (to verify equal pulldown of Tat). The BRD4 peptides are visualized by autoradiography after SDS/PAGE.