Potent Suppression of Viral Infectivity by the Peptides That Inhibit Multimerization of Human Immunodeficiency Virus Type 1 (HIV-1) Vif Proteins (2003)

Virion infectivity factor (Vif) is essential for the replication of human immunodeficiency virus type 1 (HIV-1) in vivo, but its function remains uncertain. Recently, we have shown that Vif proteins are able to form multimers, including dimers, trimers, or tetramers. Because the multimerization of Vif proteins is required for Vif function in the viral life cycle, we propose that it could be a novel target for anti-HIV-1 therapeutics. Through a phage peptide display method, we have identified a set of 12-mer peptides containing a PXP motif that binds to HIV-1 Vif protein. These proline-enriched peptides potently inhibited the Vif-Vif interaction in vitro. We have also screened a set of synthesized Vif peptides (15-mer), which covers all the amino acids of the HIV-1 Vif protein sequence, for their ability to inhibit the Vif-Vif interaction in vitro. We demonstrated that Vif-derived proline-enriched peptides that contain the161PPLP164 domain are able to inhibit the Vif-Vif interaction. Conversely, the deletion of the161PPLP164 domain of Vif protein will significantly impair the capability of Vif proteins to interact with each other, indicating that the 161PPLP164domain plays a key role in Vif multimerization. All these results demonstrate that the proline-enriched peptides block the multimerization of Vif through interfering with the polyproline interfaces of Vif formed by 161PPLP164 domain. Moreover, these peptides which inhibit the Vif-Vif interaction in vitro potently inhibit HIV-1 replication in the “nonpermissive” T-cells. We propose that this study starts a novel strategy to develop structural diverse inhibitors of Vif such as peptidomimetics or small organic molecules. Virion infectivity factor (Vif) is essential for the replication of human immunodeficiency virus type 1 (HIV-1) in vivo, but its function remains uncertain. Recently, we have shown that Vif proteins are able to form multimers, including dimers, trimers, or tetramers. Because the multimerization of Vif proteins is required for Vif function in the viral life cycle, we propose that it could be a novel target for anti-HIV-1 therapeutics. Through a phage peptide display method, we have identified a set of 12-mer peptides containing a PXP motif that binds to HIV-1 Vif protein. These proline-enriched peptides potently inhibited the Vif-Vif interaction in vitro. We have also screened a set of synthesized Vif peptides (15-mer), which covers all the amino acids of the HIV-1 Vif protein sequence, for their ability to inhibit the Vif-Vif interaction in vitro. We demonstrated that Vif-derived proline-enriched peptides that contain the161PPLP164 domain are able to inhibit the Vif-Vif interaction. Conversely, the deletion of the161PPLP164 domain of Vif protein will significantly impair the capability of Vif proteins to interact with each other, indicating that the 161PPLP164domain plays a key role in Vif multimerization. All these results demonstrate that the proline-enriched peptides block the multimerization of Vif through interfering with the polyproline interfaces of Vif formed by 161PPLP164 domain. Moreover, these peptides which inhibit the Vif-Vif interaction in vitro potently inhibit HIV-1 replication in the “nonpermissive” T-cells. We propose that this study starts a novel strategy to develop structural diverse inhibitors of Vif such as peptidomimetics or small organic molecules. Virion infectivity factor (Vif) 1The abbreviations used are: Vif, virion infectivity factor; HIV-1, human immunodeficiency virus type 1; GST, glutathione S-transferase; ELISA, enzyme-linked immunosorbent assay; HPLC, high performance liquid chromatography; Ant, antennapedia; PBS, phosphate-buffered saline 1The abbreviations used are: Vif, virion infectivity factor; HIV-1, human immunodeficiency virus type 1; GST, glutathione S-transferase; ELISA, enzyme-linked immunosorbent assay; HPLC, high performance liquid chromatography; Ant, antennapedia; PBS, phosphate-buffered saline protein of HIV-1 is required for viral replication in vivo (1Wieland U. Hartmann J. Suhr H. Salzberger B. Eggers H.J. Kuhn J.E. Virology. 1994; 203: 43-51Google Scholar, 2Sova P. van Ranst M. Gupta P. Balachandran R. Chao W. Itescu S. McKinley G. Volsky D.J. J. Virol. 1995; 69: 2557-2564Google Scholar). In cell culture systems, HIV-1Δvif viruses are incapable of establishing infection in certain cells, such as H9 T-cells, peripheral blood lymphocytes, and monocyte-derived macrophages (3Gabuzda D.H. Lawrence K. Langhoff E. Terwilliger E. Dorfman T. Haseltine W.A. Sodroski J. J. Virol. 1992; 66: 6489-6495Google Scholar, 4Strebel K. Daugherty D. Clouse K. Cohen D. Folks T. Martin M.A. Nature. 1987; 328: 728-730Google Scholar, 5Gabuzda D.H. Li H. Lawrence K. Vasir B.S. Crawford K. Langhoff E. J. Acquired Immune Defic. Syndr. 1994; 7: 908-915Google Scholar, 6Dornadula G. Yang S. Pomerantz R.J. Zhang H. J. Virol. 2000; 74: 2594-2602Google Scholar). HIV-1 viruses with a defective vif gene are not able to complete intracellular reverse transcription and endogenous reverse transcription in cell-free virions when mild detergent is utilized to make the viral envelope permeable (7Courcoul M. Patience C. Rey F. Blanc D. Harmache A. Sire J. Vigne R. Spire B. J. Virol. 1995; 69: 2068-2074Google Scholar, 8Goncalves J. Korin Y. Zack J. Gabuzda D. J. Virol. 1996; 70: 8701-8709Google Scholar, 9Sova P. Volsky D.J. J. Virol. 1993; 67: 6322-6326Google Scholar, 10von Schwedler U. Song J. Aiken C. Trono D. J. Virol. 1993; 67: 4945-4955Google Scholar). Most studies indicated that the expression of viral components, including viral proteins and nucleic acids, is not altered in the virions produced from nonpermissive cells (3Gabuzda D.H. Lawrence K. Langhoff E. Terwilliger E. Dorfman T. Haseltine W.A. Sodroski J. J. Virol. 1992; 66: 6489-6495Google Scholar, 10von Schwedler U. Song J. Aiken C. Trono D. J. Virol. 1993; 67: 4945-4955Google Scholar, 11Fouchier R.A. Simon J.H. Jaffe A.B. Malim M.H. J. Virol. 1996; 70: 8263-8269Google Scholar). However, the deletion of thevif gene will result in alterations of virion morphology (12Borman A.M. Quillent C. Charneau P. Dauguet C. Clavel F. J. Virol. 1995; 69: 2058-2067Google Scholar, 13Bouyac M. Courcoul M. Bertoia G. Baudat Y. Gabuzda D. Blanc D. Chazal N. Boulanger P. Sire J. Vigne R. Spire B. J. Virol. 1997; 71: 9358-9365Google Scholar, 14Hoglund S. Ohagen A. Lawrence K. Gabuzda D. Virology. 1994; 201: 349-355Google Scholar). Various hypotheses have been proposed regarding the molecular mechanisms of Vif protein. It has been reported that defect ofvif could affect the maturation of Gag precursor (15Simm M. Shahabuddin M. Chao W. Allan J.S. Volsky D.J. J. Virol. 1995; 69: 4582-4586Google Scholar). Furthermore, Vif could directly bind to the protease domain ofpol precursor and prevent the improper cleavage of Gag precursors before viral assembly (16Potash M.J. Bentsman G. Muir T. Krachmarov C. Sova P. Volsky D.J. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 13865-13868Google Scholar). It was also proposed that Vif protein is required to counteract an unknown endogenous inhibitor(s) in the virus-producing cells (17Madani N. Kabat D. J. Virol. 1998; 72: 10251-10255Google Scholar, 18Simon J.H. Gaddis N.C. Fouchier R.A. Malim M.H. Nat. Med. 1998; 4: 1397-1400Google Scholar). Recent studies further indicated this endogenous inhibitor is CEM15, which is only expressed in the nonpermissive cells. Introduction of CEM15 into the permissive cells will generate a nonpermissive phenotype (19Sheehy A.M. Gaddis N.C. Choi J.D. Malim M.H. Nature. 2002; 418: 646-650Google Scholar). However, the function of CEM15 remains unknown. Because its sequence is similar with APOBEC-1(apoB mRNA-editing catalytic subunit 1), a cytidine deaminase that can change cytidine into uridine in the mRNA of apolipoprotein B, CEM15 could affect the genomic RNA of HIV-1. Interestingly, we and others show that Vif is an RNA-binding protein and is an integral component of a messenger ribonucleotide protein complex of viral RNA (20Zhang H. Pomerantz R.J. Dornadula G. Sun Y. J. Virol. 2000; 74: 8252-8261Google Scholar, 21Dettenhofer M. Cen S. Carlson B.A. Kleiman L. Yu X.F. J. Virol. 2000; 74: 8938-8945Google Scholar). The Vif protein in this ribonucleoprotein complex may protect viral RNA from various endogenous inhibitors and could mediate viral RNA engagement with HIV-1 Gag precursors. As such, Vif could play a key role in the proper trafficking of the viral genetic substance (genomic RNA) in the lentivirus-producing cells.Because Vif is essential for HIV-1 replication, it is an important target for anti-HIV therapeutics. However, because its molecular mechanism in viral life cycle remains to be further determined, it is quite difficult to generate a small molecule inhibitor(s) to block Vif function at the present time. Recently, we have found that Vif proteins are able to form multimer (22Yang S. Sun Y. Zhang H. J. Biol. Chem. 2001; 276: 4889-4893Google Scholar). It is well known that multimerization is critical to the biological activity of many prokaryotic and eukaryotic proteins and is a common mechanism for the functional activation/inactivation of proteins. Therefore, multimerization has been an ideal target for the development of inhibitors of various proteins (23Angers S. Salahpour A. Bouvier M. Annu. Rev. Pharmacol. Toxicol. 2002; 42: 409-435Google Scholar, 24Cochran A.G. Chem. Biol. 2000; 7: 85-94Google Scholar, 25Huang Z. Pharmacol. Ther. 2000; 86: 201-215Google Scholar).In this report, we demonstrate that Vif multimerization could be a promising intervention target for anti-HIV-1 agent development. We have found that a set of proline-enriched peptides is able to bind to Vif protein, inhibit the Vif-Vif interaction, and inhibit viral replication in cell culture. Our data demonstrates that, although the function and structure of Vif remains uncertain, we have still successfully developed the potent Vif antagonists, based upon the biochemical characteristics of Vif protein.DISCUSSIONWe have demonstrated that the151AALIKPKQIKPPLP164 domain of HIV-1 Vif is critical for Vif multimerization, which is required for Vif function (22Yang S. Sun Y. Zhang H. J. Biol. Chem. 2001; 276: 4889-4893Google Scholar). In this report, we have further demonstrated that the161PPLP164 domain plays a key role in Vif-Vif interaction. Our current results suggest that Vif-Vif binding occurs, at least in through the interaction in each Vif Because the function of Vif remains it is difficult to the molecular mechanism regarding Vif multimerization is required for Vif However, studies that Vif is required to counteract the endogenous inhibitor CEM15, which is a cytidine deaminase (19Sheehy A.M. Gaddis N.C. Choi J.D. Malim M.H. Nature. 2002; 418: 646-650Google Scholar, R.J. Nature. 2002; 418: Scholar). Because Vif binds to HIV-1 it is to that binding could protect the from RNA (20Zhang H. Pomerantz R.J. Dornadula G. Sun Y. J. Virol. 2000; 74: 8252-8261Google Scholar, 21Dettenhofer M. Cen S. Carlson B.A. Kleiman L. Yu X.F. J. Virol. 2000; 74: 8938-8945Google Scholar). binding could be the mechanism for Vif It is quite important to study the binding and Vif-Vif interaction. Because Vif binds to RNA through its Vif-Vif interaction at the Vif-Vif interaction could be with Conversely, Vif is able to bind with Gag protein through the amino acids in the at the and Vif binds to also through the161PPLP164 domain. Therefore, the Vif-Vif interaction could be with binding or binding M. Courcoul M. Bertoia G. Baudat Y. Gabuzda D. Blanc D. Chazal N. Boulanger P. Sire J. Vigne R. Spire B. J. Virol. 1997; 71: 9358-9365Google Scholar, G. Courcoul M. G. Y. C. D. Y. Vigne R. E. J. Biol. Chem. 2001; 276: Scholar). These hypotheses to be phage display peptide a set of proline-enriched peptides binding to Vif was identified and is able to block the Vif-Vif interaction. The proline-enriched sequence is a and binds to the of in M. J. 2000; Scholar). Vif-Vif interaction could the or the161PPLP164 and in the Vif protein. It that the PXP peptides the structure of the161PPLP164 domain and bind to the of Vif, which is quite critical for Vif multimerization. these proline-enriched the peptides containing the motif have the binding to Vif protein. We have also the synthesized peptides from the Vif protein upon Vif-Vif interaction. Our data demonstrated that the peptides containing the 161PPLP164 domain are able to inhibit Vif-Vif interaction, indicating that the161PPLP164 domain plays a key role in Vif-Vif this report, we demonstrated that proline-enriched PXP peptides not only inhibit Vif-Vif interaction but also the binding Vif and It is that the PXP peptides have been shown to inhibit the of various protein M. J. 2000; Scholar, A.B. J.E. Proc. Natl. Acad. Sci. U. S. A. 1996; Scholar). Because the peptides identified in this not have to the cells at used to inhibit HIV-1 replication, have certain in Vif-Vif or the of protein used in the of the cells.Because Vif is required for HIV-1 replication and Vif multimerization is important for the function of Vif, the inhibitor(s) that the of Vif multimer inhibit HIV-1 was used to the peptides that inhibit Vif-Vif interaction to cells. the peptides that inhibit Vif-Vif interaction potently inhibit HIV-1 replication in cell culture this report, we have shown that the161PPLP164 domain of Vif is a target for Vif Because the PXP peptides potently inhibit Vif-Vif interaction and inhibit HIV-1 replication in nonpermissive cells, it is to further the structural mechanisms of these peptide inhibitors and develop potent Vif such as or small organic molecular Because of the essential role of Vif in HIV-1 replication, we that the development of these Vif inhibitors may a strategy for T. R. 1997; Scholar, Proc. Pharmacol. 1997; Scholar). Virion infectivity factor (Vif) 1The abbreviations used are: Vif, virion infectivity factor; HIV-1, human immunodeficiency virus type 1; GST, glutathione S-transferase; ELISA, enzyme-linked immunosorbent assay; HPLC, high performance liquid chromatography; Ant, antennapedia; PBS, phosphate-buffered saline 1The abbreviations used are: Vif, virion infectivity factor; HIV-1, human immunodeficiency virus type 1; GST, glutathione S-transferase; ELISA, enzyme-linked immunosorbent assay; HPLC, high performance liquid chromatography; Ant, antennapedia; PBS, phosphate-buffered saline protein of HIV-1 is required for viral replication in vivo (1Wieland U. Hartmann J. Suhr H. Salzberger B. Eggers H.J. Kuhn J.E. Virology. 1994; 203: 43-51Google Scholar, 2Sova P. van Ranst M. Gupta P. Balachandran R. Chao W. Itescu S. McKinley G. Volsky D.J. J. Virol. 1995; 69: 2557-2564Google Scholar). In cell culture systems, HIV-1Δvif viruses are incapable of establishing infection in certain cells, such as H9 T-cells, peripheral blood lymphocytes, and monocyte-derived macrophages (3Gabuzda D.H. Lawrence K. Langhoff E. Terwilliger E. Dorfman T. Haseltine W.A. Sodroski J. J. Virol. 1992; 66: 6489-6495Google Scholar, 4Strebel K. Daugherty D. Clouse K. Cohen D. Folks T. Martin M.A. Nature. 1987; 328: 728-730Google Scholar, 5Gabuzda D.H. Li H. Lawrence K. Vasir B.S. Crawford K. Langhoff E. J. Acquired Immune Defic. Syndr. 1994; 7: 908-915Google Scholar, 6Dornadula G. Yang S. Pomerantz R.J. Zhang H. J. Virol. 2000; 74: 2594-2602Google Scholar). HIV-1 viruses with a defective vif gene are not able to complete intracellular reverse transcription and endogenous reverse transcription in cell-free virions when mild detergent is utilized to make the viral envelope permeable (7Courcoul M. Patience C. Rey F. Blanc D. Harmache A. Sire J. Vigne R. Spire B. J. Virol. 1995; 69: 2068-2074Google Scholar, 8Goncalves J. Korin Y. Zack J. Gabuzda D. J. Virol. 1996; 70: 8701-8709Google Scholar, 9Sova P. Volsky D.J. J. Virol. 1993; 67: 6322-6326Google Scholar, 10von Schwedler U. Song J. Aiken C. Trono D. J. Virol. 1993; 67: 4945-4955Google Scholar). Most studies indicated that the expression of viral components, including viral proteins and nucleic acids, is not altered in the virions produced from nonpermissive cells (3Gabuzda D.H. Lawrence K. Langhoff E. Terwilliger E. Dorfman T. Haseltine W.A. Sodroski J. J. Virol. 1992; 66: 6489-6495Google Scholar, 10von Schwedler U. Song J. Aiken C. Trono D. J. Virol. 1993; 67: 4945-4955Google Scholar, 11Fouchier R.A. Simon J.H. Jaffe A.B. Malim M.H. J. Virol. 1996; 70: 8263-8269Google Scholar). However, the deletion of thevif gene will result in alterations of virion morphology (12Borman A.M. Quillent C. Charneau P. Dauguet C. Clavel F. J. Virol. 1995; 69: 2058-2067Google Scholar, 13Bouyac M. Courcoul M. Bertoia G. Baudat Y. Gabuzda D. Blanc D. Chazal N. Boulanger P. Sire J. Vigne R. Spire B. J. Virol. 1997; 71: 9358-9365Google Scholar, 14Hoglund S. Ohagen A. Lawrence K. Gabuzda D. Virology. 1994; 201: 349-355Google Scholar). Various hypotheses have been proposed regarding the molecular mechanisms of Vif protein. It has been reported that defect ofvif could affect the maturation of Gag precursor (15Simm M. Shahabuddin M. Chao W. Allan J.S. Volsky D.J. J. Virol. 1995; 69: 4582-4586Google Scholar). Furthermore, Vif could directly bind to the protease domain ofpol precursor and prevent the improper cleavage of Gag precursors before viral assembly (16Potash M.J. Bentsman G. Muir T. Krachmarov C. Sova P. Volsky D.J. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 13865-13868Google Scholar). It was also proposed that Vif protein is required to counteract an unknown endogenous inhibitor(s) in the virus-producing cells (17Madani N. Kabat D. J. Virol. 1998; 72: 10251-10255Google Scholar, 18Simon J.H. Gaddis N.C. Fouchier R.A. Malim M.H. Nat. Med. 1998; 4: 1397-1400Google Scholar). Recent studies further indicated this endogenous inhibitor is CEM15, which is only expressed in the nonpermissive cells. Introduction of CEM15 into the permissive cells will generate a nonpermissive phenotype (19Sheehy A.M. Gaddis N.C. Choi J.D. Malim M.H. Nature. 2002; 418: 646-650Google Scholar). However, the function of CEM15 remains unknown. Because its sequence is similar with APOBEC-1(apoB mRNA-editing catalytic subunit 1), a cytidine deaminase that can change cytidine into uridine in the mRNA of apolipoprotein B, CEM15 could affect the genomic RNA of HIV-1. Interestingly, we and others show that Vif is an RNA-binding protein and is an integral component of a messenger ribonucleotide protein complex of viral RNA (20Zhang H. Pomerantz R.J. Dornadula G. Sun Y. J. Virol. 2000; 74: 8252-8261Google Scholar, 21Dettenhofer M. Cen S. Carlson B.A. Kleiman L. Yu X.F. J. Virol. 2000; 74: 8938-8945Google Scholar). The Vif protein in this ribonucleoprotein complex may protect viral RNA from various endogenous inhibitors and could mediate viral RNA engagement with HIV-1 Gag precursors. As such, Vif could play a key role in the proper trafficking of the viral genetic substance (genomic RNA) in the lentivirus-producing cells. Because Vif is essential for HIV-1 replication, it is an important target for anti-HIV therapeutics. However, because its molecular mechanism in viral life cycle remains to be further determined, it is quite difficult to generate a small molecule inhibitor(s) to block Vif function at the present time. Recently, we have found that Vif proteins are able to form multimer (22Yang S. Sun Y. Zhang H. J. Biol. Chem. 2001; 276: 4889-4893Google Scholar). It is well known that multimerization is critical to the biological activity of many prokaryotic and eukaryotic proteins and is a common mechanism for the functional activation/inactivation of proteins. Therefore, multimerization has been an ideal target for the development of inhibitors of various proteins (23Angers S. Salahpour A. Bouvier M. Annu. Rev. Pharmacol. Toxicol. 2002; 42: 409-435Google Scholar, 24Cochran A.G. Chem. Biol. 2000; 7: 85-94Google Scholar, 25Huang Z. Pharmacol. Ther. 2000; 86: 201-215Google Scholar). In this report, we demonstrate that Vif multimerization could be a promising intervention target for anti-HIV-1 agent development. We have found that a set of proline-enriched peptides is able to bind to Vif protein, inhibit the Vif-Vif interaction, and inhibit viral replication in cell culture. Our data demonstrates that, although the function and structure of Vif remains uncertain, we have still successfully developed the potent Vif antagonists, based upon the biochemical characteristics of Vif protein. have demonstrated that the151AALIKPKQIKPPLP164 domain of HIV-1 Vif is critical for Vif multimerization, which is required for Vif function (22Yang S. Sun Y. Zhang H. J. Biol. Chem. 2001; 276: 4889-4893Google Scholar). In this report, we have further demonstrated that the161PPLP164 domain plays a key role in Vif-Vif interaction. Our current results suggest that Vif-Vif binding occurs, at least in through the interaction in each Vif Because the function of Vif remains it is difficult to the molecular mechanism regarding Vif multimerization is required for Vif However, studies that Vif is required to counteract the endogenous inhibitor CEM15, which is a cytidine deaminase (19Sheehy A.M. Gaddis N.C. Choi J.D. Malim M.H. Nature. 2002; 418: 646-650Google Scholar, R.J. Nature. 2002; 418: Scholar). Because Vif binds to HIV-1 it is to that binding could protect the from RNA (20Zhang H. Pomerantz R.J. Dornadula G. Sun Y. J. Virol. 2000; 74: 8252-8261Google Scholar, 21Dettenhofer M. Cen S. Carlson B.A. Kleiman L. Yu X.F. J. Virol. 2000; 74: 8938-8945Google Scholar). binding could be the mechanism for Vif It is quite important to study the binding and Vif-Vif interaction. Because Vif binds to RNA through its Vif-Vif interaction at the Vif-Vif interaction could be with Conversely, Vif is able to bind with Gag protein through the amino acids in the at the and Vif binds to also through the161PPLP164 domain. Therefore, the Vif-Vif interaction could be with binding or binding M. Courcoul M. Bertoia G. Baudat Y. Gabuzda D. Blanc D. Chazal N. Boulanger P. Sire J. Vigne R. Spire B. J. Virol. 1997; 71: 9358-9365Google Scholar, G. Courcoul M. G. Y. C. D. Y. Vigne R. E. J. Biol. Chem. 2001; 276: Scholar). These hypotheses to be phage display peptide a set of proline-enriched peptides binding to Vif was identified and is able to block the Vif-Vif interaction. The proline-enriched sequence is a and binds to the of in M. J. 2000; Scholar). Vif-Vif interaction could the or the161PPLP164 and in the Vif protein. It that the PXP peptides the structure of the161PPLP164 domain and bind to the of Vif, which is quite critical for Vif multimerization. these proline-enriched the peptides containing the motif have the binding to Vif protein. We have also the synthesized peptides from the Vif protein upon Vif-Vif interaction. Our data demonstrated that the peptides containing the 161PPLP164 domain are able to inhibit Vif-Vif interaction, indicating that the161PPLP164 domain plays a key role in Vif-Vif this report, we demonstrated that proline-enriched PXP peptides not only inhibit Vif-Vif interaction but also the binding Vif and It is that the PXP peptides have been shown to inhibit the of various protein M. J. 2000; Scholar, A.B. J.E. Proc. Natl. Acad. Sci. U. S. A. 1996; Scholar). Because the peptides identified in this not have to the cells at used to inhibit HIV-1 replication, have certain in Vif-Vif or the of protein used in the of the cells.Because Vif is required for HIV-1 replication and Vif multimerization is important for the function of Vif, the inhibitor(s) that the of Vif multimer inhibit HIV-1 was used to the peptides that inhibit Vif-Vif interaction to cells. the peptides that inhibit Vif-Vif interaction potently inhibit HIV-1 replication in cell culture this report, we have shown that the161PPLP164 domain of Vif is a target for Vif Because the PXP peptides potently inhibit Vif-Vif interaction and inhibit HIV-1 replication in nonpermissive cells, it is to further the structural mechanisms of these peptide inhibitors and develop potent Vif such as or small organic molecular Because of the essential role of Vif in HIV-1 replication, we that the development of these Vif inhibitors may a strategy for T. R. 1997; Scholar, Proc. Pharmacol. 1997; Scholar). We have demonstrated that the151AALIKPKQIKPPLP164 domain of HIV-1 Vif is critical for Vif multimerization, which is required for Vif function (22Yang S. Sun Y. Zhang H. J. Biol. Chem. 2001; 276: 4889-4893Google Scholar). In this report, we have further demonstrated that the161PPLP164 domain plays a key role in Vif-Vif interaction. Our current results suggest that Vif-Vif binding occurs, at least in through the interaction in each Vif Because the function of Vif remains it is difficult to the molecular mechanism regarding Vif multimerization is required for Vif However, studies that Vif is required to counteract the endogenous inhibitor CEM15, which is a cytidine deaminase (19Sheehy A.M. Gaddis N.C. Choi J.D. Malim M.H. Nature. 2002; 418: 646-650Google Scholar, R.J. Nature. 2002; 418: Scholar). Because Vif binds to HIV-1 it is to that binding could protect the from RNA (20Zhang H. Pomerantz R.J. Dornadula G. Sun Y. J. Virol. 2000; 74: 8252-8261Google Scholar, 21Dettenhofer M. Cen S. Carlson B.A. Kleiman L. Yu X.F. J. Virol. 2000; 74: 8938-8945Google Scholar). binding could be the mechanism for Vif It is quite important to study the binding and Vif-Vif interaction. Because Vif binds to RNA through its Vif-Vif interaction at the Vif-Vif interaction could be with Conversely, Vif is able to bind with Gag protein through the amino acids in the at the and Vif binds to also through the161PPLP164 domain. Therefore, the Vif-Vif interaction could be with binding or binding M. Courcoul M. Bertoia G. Baudat Y. Gabuzda D. Blanc D. Chazal N. Boulanger P. Sire J. Vigne R. Spire B. J. Virol. 1997; 71: 9358-9365Google Scholar, G. Courcoul M. G. Y. C. D. Y. Vigne R. E. J. Biol. Chem. 2001; 276: Scholar). These hypotheses to be Through phage display peptide a set of proline-enriched peptides binding to Vif was identified and is able to block the Vif-Vif interaction. The proline-enriched sequence is a and binds to the of in M. J. 2000; Scholar). Vif-Vif interaction could the or the161PPLP164 and in the Vif protein. It that the PXP peptides the structure of the161PPLP164 domain and bind to the of Vif, which is quite critical for Vif multimerization. these proline-enriched the peptides containing the motif have the binding to Vif protein. We have also the synthesized peptides from the Vif protein upon Vif-Vif interaction. Our data demonstrated that the peptides containing the 161PPLP164 domain are able to inhibit Vif-Vif interaction, indicating that the161PPLP164 domain plays a key role in Vif-Vif interaction. In this report, we demonstrated that proline-enriched PXP peptides not only inhibit Vif-Vif interaction but also the binding Vif and It is that the PXP peptides have been shown to inhibit the of various protein M. J. 2000; Scholar, A.B. J.E. Proc. Natl. Acad. Sci. U. S. A. 1996; Scholar). Because the peptides identified in this not have to the cells at used to inhibit HIV-1 replication, have certain in Vif-Vif or the of protein used in the of the cells. Because Vif is required for HIV-1 replication and Vif multimerization is important for the function of Vif, the inhibitor(s) that the of Vif multimer inhibit HIV-1 was used to the peptides that inhibit Vif-Vif interaction to cells. the peptides that inhibit Vif-Vif interaction potently inhibit HIV-1 replication in cell culture In this report, we have shown that the161PPLP164 domain of Vif is a target for Vif Because the PXP peptides potently inhibit Vif-Vif interaction and inhibit HIV-1 replication in nonpermissive cells, it is to further the structural mechanisms of these peptide inhibitors and develop potent Vif such as or small organic molecular Because of the essential role of Vif in HIV-1 replication, we that the development of these Vif inhibitors may a strategy for T. R. 1997; Scholar, Proc. Pharmacol. 1997; Scholar). We the of and for HIV-1 Vif