Plays a role in nuclear translocation of the viral pre-integration complex (PIC), thus is required for the virus to infect non-dividing cells. Targets specific host proteins for degradation by the 26S proteasome. Acts by associating with the cellular CUL4A-DDB1 E3 ligase complex through direct interaction with host VPRPB/DCAF-1. This change in the E3 ligase substrate specificity results in the degradation of host SAMHD1. In turn, SAMHD1 depletion allows viral replication in host myeloid cells by preventing SAMHD1-mediated hydrolysis of intracellular dNTPs necessary for reverse transcription (By similarity). Interacts with the P6 region of unprocessed GAG. Interacts with host VPRBP/DCAF1, leading to change substrate specificity of the CUL4A-DDB1 E3 ligase complex (By similarity). Nuclear just after virion uncoating, or if expressed in the absence of unprocessed GAG. Belongs to the lentivirus VPX protein family.