HPBP represses HIV-1 gene transcription and replication. 1G5 cells were transfected with the pNL4.3 provirus. (1) Mock, (2) HPBP/HPNO1 (50 nM), (3) HPBP (50 nM), (4) HPON1 (50 nM), and (5) AZT (10 μM) was added 24 h post transfection. Luciferase activity (A) and HIV-1 replication (B) were monitored 48 h post transfection. Values correspond to an average of at least three independent experiments carried out in duplicate. The purity and the size of purified-HPBP were controlled by SDS-PAGE and coomassie blue staining (C).