Molecular Mechanism And Arm-race Evolution Of HIV/SIV Vpx Interacts With Host Restriction Factor SAMHD1

HIV-2and closely related SIV accessory protein Vpx inactives with hostrestriction factor SAMHD1and enhances viral infection in macrophages, dendriticcells and resting CD4T cells. Previous studies has identified that Vpx hijackedCRL4(DCAF1) E3ligase to induce SAMHD1ubiquitination and degradation.However, the cellular regulation of Vpx functions and the evolutionary relationshipbetween Vpx and SAMHD1.In present study, we investigated the molecular mechanism and competiveevolution of Vpx and SAMHD1interaction. The whole project could be divided into4sections:(1) Molecular model of Vpx interacts with the adaptor of CRL4E3ligaseDCAF1;(2)Critical regions of SAMHD1is important for Vpx function;(3) The roleof neddylation on Vpx-CRL4(DCAF1) induced SAMHD1degradation;(4) Arm-raceevolution between diverse Vpx protein and primate SAMHD1protein.In this study, by structural prediction analysis of protein-protein interaction, andcompared Vpx wild type with different mutants, we found that Vpx Helix1wasessential for Vpx-DCAF1interaction and Vpx-dependent HIV-1infection inmacrophages. By viral sequences alignment analysis, we also domanstrated that VprHelix1participated in Vpr-DCAF1interaction and Vpr-induced cell cycle arrest. Ourresults suggest that Viral protein Vpx and Vpr utilize Wx4Φx2Φx3AΦxH motif torecognize DCAF1.Subsequently, we discovered a nuclear location sequences (NLS) in the Nterminal SAMHD1is essential for SAMHD1nuclear accumulation. The NLSmutanted SAMHD1is resistant to Vpx induced degradation,which indicated thatVpx-CRL4(DCAF1) induced SAMHD1in nucleus. Next, we mapped the criticalregions that affected Vpx-mediated degradation in SAMHD1. Our results showed that the deletion of HD domain or linker region in SAMHD1did not influence Vpxbinding but were not sensitive to Vpx-induced degradation. These results reveal theprotein characteristics of SAMHD1are important for Vpx function.Cellular neddylation is a dominant factor fo the Cullin Ring E3ligase activation.Here, we confirmed a first-in-class neddylation inhibitor MLN4924potently impairedVpx-induced SAMHD1degradation and blocked Vpx-depedent HIV-1infection.Further studies identified that UBE2M is responsed to neddylation ofVpx-CRL4(DCAF1) E3ligase. The critical role of neddylation on Vpx functionwould be a poteintial drug target.Based on the above studies, we investigated the ability of diverse Vpx-inducedprimate SAMHD1degradation, and shed lights on a novel evolutionary modelbetween viral protein and host restriction factor: Due to the selective pressure fromVpx, primates SAMHD1were undergoing positive selection to evade Vpx-induceddegradation.While Vpx also gained of mutantions to adapt with the changingSAMHD1.All in all, our findings on viral protein Vpx with host protein SAMHD1increaseour understanding the arm race competition between Vpx and SAMHD1, whichwould be a valuable durg target fot anti-HIV-1therapy.