The function of PAAF1 (proteasomal ATPase associated factor 1, Ensembl gene identifier ENSG00000175575) is as follows. Inhibits proteasome 26S assembly and proteolytic activity by impairing the association of the 19S regulatory complex with the 20S core. In case of HIV-1 infection, recruited by viral Tat to the HIV-1 promoter, where it promotes the recruitment of 19S regulatory complex through dissociation of the proteasome 26S. This presumably promotes provirus transcription efficiency. Protects SUPT6H from proteasomal degradation. {ECO:0000269|PubMed:15831487, ECO:0000269|PubMed:17289585, ECO:0000269|PubMed:22316138}.