HIV-2 viral protein X (Vpx) ubiquitination is dispensable for ubiquitin ligase interaction and effects on macrophage infection

HIV-2 Vpx, a virus-associated accessory protein, is critical for infection of non-dividing myeloid cells. To understand the function of Vpx ubiquitination, interaction with an E3 ubiquitin ligase complex, and ability to overcome an inhibition of reverse transcription, we analyzed Vpx lysine mutants for their function and replication capability in macrophages. Both Wt Vpx and Vpx TA (lysine-less Vpx) localized to the cytoplasm and nucleus in HeLa cells. All HIV-2 Vpx lysine mutants were functional in virion packaging. However, ubiquitination was absent with Vpx TA and Vpx K84A mutants, indicating a lack of ubiquitin on positions K68 and K77. Mutants Vpx K68A and K77A were unable to infect macrophages due to impaired reverse transcription from loss of interaction with the ubiquitin substrate receptor, DCAF1. Even though Vpx K84A lacked ubiquitination, it bound DCAF1, and infected macrophages comparable to Wt Vpx.