Izumi T, Io K, Matsui M, Shirakawa K, Shinohara M, Nagai Y, Kawahara M, Kobayashi M, Kondoh H, Misawa N, Koyanagi Y, Uchiyama T, Takaori-Kondo A. the p2 region of Pr55Gag, which are important for virus assembly and maturation, were involved in the interaction. Transduction of CD4+ T cells with BIV Vif blocked HIV-1 replication. Thus, the conserved Vif-Pr55Gag interaction provides a potential target for the future development of antiviral strategies. IMPORTANCE The conserved Vif accessory proteins of primate lentiviruses HIV-1, simian immunodeficiency virus (SIV), and BIV all form ubiquitin ligase complexes to target host antiviral APOBEC3 proteins for degradation, with different cellular requirements and using different molecular mechanisms. Here, we demonstrate that BIV Vif can interfere with HIV-1 Gag maturation and suppress Rabbit Polyclonal to PHLDA3 HIV-1 replication through interaction with the precursor of the Gag (Pr55Gag) of HIV-1 in virus-producing cells. Moreover, the HIV-1 and SIV Vif proteins are conserved in terms of their interactions with HIV-1 Pr55Gag although HIV-1 Vif proteins bind Pr55Gag less efficiently than those of BIV Vif. Our research not only sheds new light on this feature of these conserved lentiviral Vif proteins but also provides a formerly unrecognized target for the development of antiviral strategies. Since increasing the Vif-Pr55Gag interaction could potentially suppress virus proliferation, this approach could offer a new strategy for the development of HIV inhibitors. gene encodes a 23-kDa protein of 192 amino acids that Norisoboldine counteracts host antiviral factors, the apolipoprotein B mRNA-editing catalytic polypeptide-like 3 (APOBEC3) family cytidine deaminases, by recruiting host cullin-5 (Cul5)-elonginB/elonginC (CRL5) E3 ubiquitin ligase to induce APOBEC3 polyubiquitination, followed by proteasome-mediated degradation in virus-producing cells (12,C22). HIV-1 Vif function is regulated by the transcriptional factor CBF (14, 18, 23,C30). When Vif is absent from HIV-1, the host’s antiviral APOBEC3 proteins can be packaged into viral progeny and induce lethal mutation in the viruses (13, 31,C36). Another member of the lentivirus family, bovine immunodeficiency virus (BIV), was first isolated in 1969 from a cow with a wasting syndrome. This lentivirus also encodes a Vif protein of 198 amino acids (37). BIV Vif is required to overcome the antiviral activity of bovine APOBEC3 proteins (38, 39). Although the general strategy for inhibiting APOBEC3 proteins through ubiquitination is conserved between HIV-1/simian immunodeficiency virus (SIV) Norisoboldine and BIV, the cellular requirements and molecular mechanisms involved differ substantially (7, 38, 39). For example, BIV Vif recruits Cul2-CRL2 rather than Cul5-CRL5 E3 ubiquitin ligase (7, 40). Furthermore, unlike regulation of HIV-1 Vif, the regulation of BIV Vif function does not involve CBF (7, 38, 39). During lentiviral evolution, the Vif-APOBEC3 interaction Norisoboldine has been mainly been species specific: BIV Vif cannot induce the degradation of human APOBEC3 proteins, and HIV-1 Vif cannot overcome bovine APOBEC3 proteins (39, 41). Apart from their effect in counteracting the function of the antiviral APOBEC family, certain strains of HIV-1 Vif can induce G2 arrest and thus interfere with cell cycle progression and cell proliferation (42, 43). Moreover, colocalization of HIV-1 Vif and Gag at the plasma membrane has been reported (44). HIV-1 Vif has been observed to be packaged into HIV-1 and SIV virions (45,C49). Unlike Vpr, which is packaged through a specific interaction with HIV-1 Gag and at high abundance, Vif virion packaging occurs in relatively small amounts compared to its level of intracellular expression (45,C51). High-level expression of HIV-1 Vif inhibits viral infectivity by interfering with the proteolytic processing of the HIV-1 Gag precursor in released virions (49). The HIV-1 Gag precursor (Pr55Gag), the main structural protein of HIV-1 and all other retroviruses, plays diverse and crucial roles in virus replication (52). Pr55Gag is comprised of four major domains, the matrix (MAp17), capsid (CAp24), nucleocapsid (NCp7), and p6 domains, together with two spacer peptides located between CA and NC (SP1/p2) and between NC and p6 (SP2/p1) (53). These domains work in well-regulated cooperation and demonstrate the precursor protein’s multiple functions: specific trafficking to the cell membrane, recognizing and interacting with genomic RNA and both viral and host proteins, forming ordered structures required for correct viral assembly, completing budding, and stimulating the maturation of new infectious particles (54,C60). Of note, Pr55Gag completes the virus assembly, packaging, and budding in its precursor form and is cleaved by viral proteases only during or after budding. The protease cleavage rates at each of the five cleavage sites in Pr55Gag are not equivalent. Through the control of these rates, a sequential order of cleavage is maintained that is vital to.