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Identification and characterization of loop7 motif and its role in regulating biological function of human APOBEC3G
Congjie Zhai1, Ling Ma1, Zhixin Zhang1
1Institute of Medicinal Biotechnology, Chinese Academy of Medical Science, Beijing 100050, China.
Insights
Human APOBEC3G (hA3G) inhibits HIV-1, but the viral infectivity factor (Vif) targets hA3G for degradation. This study reveals loop7 controls hA3G dimerization and Vif interaction, offering a strategy to block Vif-mediated degradation.
Area of Science:
- Virology
- Molecular Biology
- Biochemistry
Background:
- Human APOBEC3G (hA3G) is a key antiviral factor inhibiting HIV-1 replication.
- The HIV-1 viral infectivity factor (Vif) protein antagonizes hA3G by promoting its proteasomal degradation.
Purpose of the Study:
- To investigate the structural and functional roles of the hA3G loop7 motif in hA3G dimerization and Vif interaction.
- To elucidate the mechanism by which Vif targets hA3G for degradation.
- To explore therapeutic strategies targeting the Vif-hA3G interaction.
Main Methods:
- Molecular modeling of hA3G dimer and hA3G-Vif complex.
- Biochemical analyses to assess protein interactions and degradation.
- Mutagenesis studies to investigate the role of loop7 residues.
Main Results:
- The loop7 motif of hA3G is crucial for both hA3G dimerization and Vif binding.
- Vif binding sterically hinders hA3G dimerization, suggesting monomeric hA3G is the substrate for Vif-mediated degradation.
- The loop7 motif regulates hA3G's biological functions, including dimerization, Vif interaction, degradation, and subcellular localization.
Conclusions:
- The hA3G loop7 motif acts as a multifunctional interface regulating hA3G's antiviral activity and Vif interaction.
- Targeting the loop7 region offers a potential strategy to inhibit Vif-mediated hA3G degradation and enhance antiviral defense.
Abstract:
Human APOBEC3G (hA3G) is a cytidine deaminase which inhibits HIV-1 replication. The HIV-1 accessory protein viral infectivity factor (Vif) counteracts with hA3G by targeting it for proteasomal degradation. In this work, we constructed and optimized molecular models of the hA3G dimer and the hA3G-Vif complex. The molecular modeling study revealed that the loop7 motif of hA3G appears on the interfaces of both the hA3G-Vif complex and the hA3G dimer. Biochemical analysis provided evidence suggesting that binding of Vif to hA3G results in steric blocking of hA3G dimerization, implying that monomeric hA3G serves as a substrate for Vif-mediated degradation. Furthermore, we presented evidence for the important roles of the loop7 motif, especially the central residues within the region, in hA3G dimerization, hA3G--Vif interaction, Vif-mediated hA3G degradation as well as subcellular localization of hA3G. This work highlights a multiple-task interface formed by loop7 motif, which regulates biological function of hA3G, thus providing the feasibility of the strategy of blocking Vif-mediated A3G degradation by targeting the putative site around loop7.
