Vpx is a protein encoded by Human Immunodeficiency Virus Type 2 (HIV-2) and specific Simian Immunodeficiency Viruses (SIVs) that is essential for successful infection of non-dividing myeloid cells. Vpx facilitates viral replication by trafficking the viral genome into the nucleus of infected cells and targeting the primarily nuclear innate immune protein SAMHD1 for proteasomal degradation. Considering that these activities occur at the nucleus, we hypothesized that Vpx nuclear localization would be tightly correlated with these functions. To assess this, site directed mutagenesis in combination with confocal microscopy or Western Blotting analyses were utilized to evaluate the determinants of nuclear accumulation and SAMHD1 antagonism for the SIVmac239 and HIV-2 ROD9 Vpx proteins. Our confocal microscopy analyses revealed that wild-type HIV-2 ROD9 Vpx efficiently localizes to the nucleus whereas wild-type SIVmac239 Vpx does not. Three residues (A/E23, A/E31, and R/E54) spanning alpha helices I and II of Vpx were shown to dictate the discrepant localization patterns observed between these proteins and were thus identified as central contributors to Vpx nuclear accumulation. Additionally, Western Blotting analyses indicated that unlike HIV-2 ROD9 Vpx, SIVmac239 Vpx is capable of substantial SAMHD1 degradation. Importantly, we also found that increasing SIVmac239 Vpx nuclear accumulation by mutating the aforementioned helix I and II Vpx residues correlated with more pronounced SAMHD1 degradation compared to wild-type SIVmac239 Vpx. The role of these Vpx residues in localization and SAMHD1 degradation has not been previously described and our findings reinforce the relevance of Vpx cellular distribution in executing tasks important for successful infection by HIV-2 and Vpxencoding SIVs. These data not only broaden our understanding of the Vpx-encoding Lentiviruses, but also provide a framework for the future development of antiviral and anticancer therapeutics.
Date of Degree
Master of Science (MS)
Program of Study
Science, Engineering and Technology
Mayhew, H. D. (2023). Novel Amino Acids dictate differences in SIVmac239 and HIV-2 ROD9 Vpx cellular localization [Master’s thesis, Minnesota State University, Mankato]. Cornerstone: A Collection of Scholarly and Creative Works for Minnesota State University, Mankato. https://cornerstone.lib.mnsu.edu/etds/1320/
Available for download on Wednesday, June 11, 2025