Abstract

The vpr gene of human immunodeficiency virus type 1 (HIV-1) plays an important role in the pathogenicity of viruses. Previous studies showed that mutation of certain sites in HIV-1 Vpr amino acid sequences might influence the clinical process of infected individuals and attenuate its apoptosis-inducing capacity on infected cells. The present study was designed to transfect hela cells with several HIV-1 vpr fragments carrying specific mutation sites, and to observe the distinction of apoptosis-inducing effects of different HIV-1 vpr variant fragments on host cells and explore the possible mechanisms. According to the previous results, 14 typical vpr variant fragments were chosen from Chinese HIV-1 infected individuals. After PCR amplification of vpr gene, the products were purified and double digested with Hind and BamHI. Then pcDNA3.1 (+) eukaryotic expression plasmids were used for the ligation and transduction experiments. The recombinant plasmids were transiently transfected into Hela cells with liposomes, and meanwhile the blank cell and empty vector cell were established as control. RT-PCR was used to detect the mRNA expression of target genes; fluorescent microscope for observing apoptotic cells with Hoechst staining; DNA agarose electrophoresis for detecting apoptotic gradient band; Annexin assay for detecting cell apoptosis; and Caspase activity test for exploring the pathway of cell apoptosis. After transfected with 14 vpr gene segments, the Hela cells exhibited various apoptosis-inducing capabilities. We found that the HIV-1 Vpr segments with mutation at the 70th, 85th, 86th, or 94th site showed lower apoptosis-inducing capabilities than other segments on Hela cells, and the apoptosis-inducing ability of HIV-1 vpr gene on host cells might be related to its subtype. Meanwhile, we found that the Caspase3 activity of transfected cell carrying these mutated fragment sites was decreased as compared to the cell with other fragments. This study firstly found that the HIV-1 Vpr fragments with the 70th, 85th, 86th, or 94th site mutation might attenuate their apoptosis-inducing abilities on Hela cells. One of the mechanisms might be the attenuation of Caspase-3 activity.

Keywords: Human immunodeficiency virus type 1, Vpr gene, Mutation, Apoptosis, Caspase pathway, Hela cell