|Ph.D Student||Aya Khwaja|
|Subject||Molecular Basis for Vif Chaperoning in the E3-Ligase|
Mediated Degradation of APOBEC3
|Department||Department of Biology||Supervisor||Dr. Alian Akram|
|Full Thesis text|
The innate immunity APOBEC (A3) proteins can attack viral genomes introducing mutations that can lead to abortive replication of infecting viruses. The viral infectivity factor (Vif) protein of HIV-1 virus can counteract A3 proteins by manipulating the E3-ligase complex resulting in A3 polyubiquitination and proteasomal degradation. Whereas Vif of primate lentiviruses crucially recruit cellular core binding factor beta (CBFβ) for this activity, nonprimate lentiviruses do not rely on CBFβ and recruit different cofactors. In this work, we characterize the conserved and non-canonical requirements of Vif in the assembly of functional A3/E3 ligase complex. We found that recombinant Vif is highly soluble but is not available in a functional form unless interacted with binding partners. HIV-1 and MVV Vif require multilevel chaperoning including a conserved EloBC and a distinct non-canonical cofactor. BIV Vif requires the binding of EloBC alone for functional folding. The chaperoning factors are needed to expose the N-terminal and C-terminal binding surfaces of A3 substrate proteins and Cullin5 of E3-ubiquitination pathway. Furthermore, we characterized the FIV Vif and revealed the conservation of a Cul-box and a distinct sequence extension compensating for the zinc binding motif found in HIV-1 Vif. Finally, we found that Vif flexibility to use alternative non-canonical cofactors appear to be of high genetic barrier that could restrict virus adaptation.