Mechanism Of Viral Protein Vpx And Vpr Bind With Host CRL4(DCAF1)E3Ligase

HIV-2and closely related SIV Vpx proteins are essential for viral replication inmacrophages and dendritic cells. Vpx hijacks DCAF1-DDB1-Cul4E3ubiquitin ligaseto promote viral replication. DCAF1is essential for cell proliferation and embryonicdevelopment and is responsible for the polyubiquitination of poorly defined cellularproteins. How substrate receptors recruit the DCAF1-containing E3ubiquitin ligase toinduce protein degradation is still poorly understood. Here we identify a highlyconserved motif (Wx4Φx2Φx3AΦxH) that is present in diverse Vpx and Vpr proteinsof primate lentiviruses. We demonstrate that the Wx4Φx2Φx3AΦxH motif in SIVmacVpx is required for both the Vpx-DCAF1interaction and/or Vpx-mediateddegradation of SAMHD1. DCAF1-binding defective Vpx mutants also have impairedability to promote SIV△Vpx virus infection of myeloid cells. Critical amino acids inthe Wx4Φx2Φx3AΦxH motif of SIV Vpx that are important for DCAF1interactionmaintained the ability to bind SAMHD1, indicating that the DCAF1and SAMHD1interactions involve distinctive interfaces in Vpx. Surprisingly, VpxW24A mutantproteins that were still capable of binding DCAF1and SAMHD1lost the ability toinduce SAMHD1degradation, suggesting that Vpx is not a simple linker between theDCAF1-DDB1-Cul4E3ubiquitin ligase and its substrate, SAMHD1. TheWx4Φx2Φx3AΦxH motif in HIV-1Vpr is also required for the Vpr-DCAF1interaction and Vpr-induced G2cell cycle arrest. Thus, our data reveal previouslyunrecognized functional interactions involved in the assembly of virally hijackedDCAF1-DDB1-based E3ubiquitin ligase complex.