The Journal of biological chemistry 2017 10 27() pii 10.1074/jbc.M117.798801
The Vpr protein is an accessory virulence factor of HIV-1 that facilitates infection in immune cells. Cellular functions of Vpr are tied to its interaction with DCAF1, a substrate receptor component of the CRL4 E3 ubiquitin ligase. Recent proteomic approaches suggested that Vpr degrades HLTF DNA helicase in a proteasome-dependent manner by redirecting the CRL4-DCAF1 E3 ligase. However, the precise molecular mechanism of Vprdependent HLTF depletion is not known. Here, using in vitro reconstitution assays, we show that Vpr mediates polyubiquitination of HLTF, by directly loading it onto the C-terminal WD40 domain of DCAF1 in complex with the CRL4 E3 ubiquitin ligase. Mutational analyses suggest that Vpr interacts with DNA binding residues in the Nterminal HIRAN domain of HLTF in a manner similar to the recruitment of another target, Uracil DNA glycosylase (UNG2), to the CRL4-DCAF1 E3 by Vpr. Strikingly, Vpr also engages a second, adjacent region, which connects the HIRAN and ATPase/helicase domains. Thus, our findings reveal that Vpr utilizes common as well as distinctive interfaces to recruit multiple post-replication DNA repair proteins to the CRL4- DCAF1 E3 ligase for ubiquitin-dependent proteasomal degradation.