Mechanism Of Viral Protein Vpx Promotes HIV Infection In Macrophages

Deoxynucleoside triphosphate hydrolase SAMHD1 protein,which is a specific antiviral restriction factor in macrophages,can effectively counteract HIVinfection in myeloid cells and resting CD4-positive T cells.HIV-2 virus and some primate immunodeficiency viruses such as SIVs can effectively promote HIV / SIV virus replication in macrophages by encoding the virus helper protein Vpx.T The ubiquitination of SAMHD1 induced by the host ubiquitination complex CRL4(DCAF1),resulting in the degradation of the SAMHD1 protein by proteasome after the ubiquitination and the release of macrophages into HIV / SIV virus Resistance are the main functions of Vpx.Previous studies have comprehensively analyzedthatthe molecular assembling mechanism of the Vpx-CRL4(DCAF1)protein complex.However,the molecular mechanism of Vpx protein’s regulating function within host cellsis still uncertain and need comprehensive investigation/further exploration.This study focus on the molecular strategy of how the viral protein Vpx can adapt to the host cell’s internal environmentand seek the evolutionary conserved molecular character of Vpx protein which can break through host restriction factor SAMHD1 as a new broad-spectrum stable and effective antiviral target.According to the content,this study can be divided into four parts,including:(1)Study on the Role of C-terminal poly-Proline tail Functional Domain in Vpx Protein in the Vpx-dependent degradation of the virus limiting factor SAMHD1 and the promotion of viral infection in macrophages;(2)Research on the molecular mechanism of C-terminal poly-Proline tail Functional Domain in Vpx Protein participating in regulating its function;(3)Study on the Mechanism of Vpx evading the regulation of CRL4(DCAF1)ubiquitin ligase inhibitory factor Merlin in host cells;(4)We have identified adominant negative mutant DCAF1,which can inhibit the activity of the Vpx protein to induce SAMHD1 proteinubiquitination-dependent degradation.This study revealed that in the evolutionary process,the helper protein Vpx of the HIV-2 / SIVsm species was found to be resistant to host proteasome-dependent degradation by encoding the C-terminal poly-proline domain which enhance the Vpx protein function Persistence.This is a molecular strategy for the viral protein to adapt to the host cell environment.At the same time,the lack of the proline domain disrupts the ability of Vpx to stabilize and effectively degrade SAMHD1,so it reduce the function of the Vpx protein.This study further confirmed that the effect of this proline-rich domain on Vpx function was accomplished by a non-CRL4(DCAF1)ubiquitin-linked proteasome degradation pathway.It also demonstrated that the reduction of Vpx in content was not associated with CRL4(DCAF1)-Vpx-SAMHD1 ubiquitin complex,when the polyproline sequence was deleted.This study also confirmed that CRL4(DCAF1)ubiquitin complex inhibitory factor Merlin has no effect on the degradation of SAMHD1 by using this ubiquitin complex,because the viral protein Vpx and ubiquitin complex inhibitory factor Merlin and DCAF1 binding region is different.The DCAF1 protein,which was deleted of the Merlin binding region,is still able to maintain Vpx degradation of SAMHD1 function.Furthermore,by studying the effect of Vpx protein evading CRL4(DCAF1)complex regulatory factor,we also identified that DCAF1(1311-1417)region is important for Vpx to recognize DCAF1 protein and CRL4(DCAF1)protein.In addition,a DCAF1(1-1311)dominant negative mutant with the effect of inhibiting viral protein Vpx degradation of the host-limiting factor SAMHD1 was identified.