The experiment was repeated for over five times. It suggests that hA3G might be a defensive factor for HCV replication. Specific siRNAs were then used to silence the endogenous hA3G gene in Huh7.5 cells. Treatment of the HCV-infected Huh7.5 cells with specific

hA3G siRNA (25 basepairs) reduced hA3G mRNA by 77% in the real-time RT-PCR assay; accordingly, intracellular HCV RNA load increased by ≈90% (Fig. 1B, upper). RNAi treatment with another siRNA sequence specific for hA3G showed a similar effect (data not shown). Accordingly, the intracellular HCV core protein level increased in parallel with the decrease of intracellular hA3G protein (Fig. 1B, lower). The results again indicated that intracellular hA3G is a host innate defensive factor against HCV. Similar to that in HIV-1 infection,17, 18 separate transfection of the HCV-infected Huh7.5 learn more cells with other APOBEC3 family members (such as hA3C and hA3F) showed strong inhibitory effect on HCV replication as well (Fig. 1C). HIV-1 accessory factor Vif is a 190-240 amino acid protein required for HIV-1 to replicate in hA3G-containing host cells.19, 20 It binds to hA3G in host cell cytoplasm and triggers hA3G ubiquitination and subsequent degradation by way of

proteasomes. It is one of the most important mechanisms for HIV-1 to escape from cellular defensive factor hA3G. To verify the role of hA3G in HCV infection, external HIV-1 Vif was introduced into the HCV-infected Huh7.5 cells using the transfection plasmid described above. As PD-1 antibody shown in Fig. 1D, after adding plasmid pVif into

HCV-infected Huh7.5 cells, the Vif protein expressed and hA3G significantly reduced in a dose-dependent manner; as a result, HCV replication increased. It appeared that the expression of transfected HIV-1 Vif caused a clearance of hA3G in the host cells, and generated an environment that favored HCV replication. The result provides another support for the observation that hA3G is a host defensive factor for HCV, and demonstrates that the presence of HIV-1 Vif protein in host cells might help HCV proliferation. It was estimated that 15%-30% of all HIV-infected persons are coinfected with HCV21; the molecular mechanism for the high incidence of HCV infection in HIV-positive individuals Carnitine dehydrogenase remains unclear. The results presented in Fig. 1 might help us to understand why HIV/HCV coinfection is common in HIV-1(+) individuals. If the above finding is true, then stabilization of hA3G should inhibit HCV replication. Thus, agents with a protective effect on hA3G were employed in the study. RN-5 (Fig. 2A, left) is a compound that protects hA3G from Vif-mediated degradation in 293T cells cotransfected with hA3G and HIV-1 Vif vectors.7 Here, RN-5 was used as a chemical probe to validate the role of hA3G in HCV replication. RN-5 treatment showed no toxicity in the Huh7.