DBR1 over-expression does not affect HIV-1 replication. (A) GHOST-R5X4 cells were transfected with various amounts of CDM9-DBR1 (1 μg/ml, 4 μg/ml, 6 μg/ml) or mock transfected for forty-eight hours. Total RNA was isolated and DBR1 expression was quantified by real-time RT-PCR. (B) GHOST-R5X4 cells were transfected with CDM9-DBR1 (black bar, CDM9-DBR1), control vector CDM9 (white bar, CDM9-DBR1) or DBR1 siRNA pHyper-D123 (black bar, DBR1 siRNA), control vector pHyper (white bar, DBR1 siRNA), or cotransfected CDM9-DBR1 and DBR1 siRNA pHyper-D123 (black bar, CDM9-DBR1 + DBR1 siRNA), control vector CDM9 and pHyper (white bar, CDM9-DBR1 + DBR1 siRNA) for forty-eight hours and then infected with HIV-1 (JR-CSF) for twenty-four hours. Supernatants were collected and p24 was assayed using a commercially available HIV-1 p24 ELISA kit. All ELISA measurements were done in triplicate. Error bars indicate standard deviations. The asterisk denotes p < 0.05 by Student's t-test.