The Ebola virus (EBOV), a member of the Filoviridae family, is a highly pathogenic agent responsible for severe hemorrhagic fever in humans. Understanding the molecular mechanisms governing its replication is critical for developing effective antiviral strategies. VP35-TurboID immunosuppression coupled with quantitative mass spectrometry identified Septin9, the host GTP-binding protein which played a role in cytoskeletal regulation, as a novel interactor of VP35. Western blotting and Far-Western blotting confirmed the direct interaction and demonstrated that the C-terminal region of VP35 was the critical binding domain. Functionally, EBOV replication as well as the formation of viral inclusion bodies (VIBs) was demonstrated to be significantly suppressed by Septin9 knockdown and depletion, as shown by the EBOV minigenome (EBOV MG) and the transcription- and replication-competent virus-like particles (trVLPs) system. This study reveals that VP35 engages in a specific interaction with the GTP-binding protein Septin9, thereby impeding EBOV replication through the disruption of inclusion bodies. The overarching objective of this study is to significantly enhance our understanding about the pathogenic mechanism of EBOV and offer a robust theoretical foundation and solid empirical support for the formulation of innovative therapeutic strategies against EBOV.
Virus Replication/physiology* ; Septins/physiology* ; Humans ; Ebolavirus/physiology* ; Inclusion Bodies, Viral/metabolism* ; Viral Regulatory and Accessory Proteins/metabolism* ; Hemorrhagic Fever, Ebola/virology*

Adult ; Female ; Gene Expression ; Glomerulonephritis, Membranous ; etiology ; genetics ; pathology ; Hepatitis B ; complications ; Hepatitis B virus ; genetics ; metabolism ; Humans ; Male ; Middle Aged ; Mutation ; Receptors, Phospholipase A2 ; genetics ; metabolism ; Trans-Activators ; genetics ; metabolism ; Viral Regulatory and Accessory Proteins ; genetics ; metabolism

To investigate whether transcription of hepatitis B virus (HBV) gene occurs in human sperm, total RNA was extracted from sperm of patients with chronic HBV infection (test-1), from donor sperm transfected with a plasmid containing the full-length HBV genome (test-2), and from nontransfected donor sperm (control), used as the template for reverse transcription-polymerase chain reaction (RT-PCR). Positive bands for HBV DNA were observed in the test groups but not in the control. Next, to identify the role of host genes in regulating viral gene transcription in sperm, total RNA was extracted from 2-cell embryos derived from hamster oocytes fertilized in vitro by HBV-transfected (test) or nontransfected (control) human sperm and successively subjected to SMART-PCR, suppression subtractive hybridization, T/A cloning, bacterial amplification, microarray hybridization, sequencing and the Basic Local Alignment Search Tool (BLAST) search to isolate differentially expressed genes. Twenty-nine sequences showing significant identity to five human gene families were identified, with chorionic somatomammotropin hormone 2 (CSH2), eukaryotic translation initiation factor 4 gamma 2 (EIF4G2), pterin-4 alpha-carbinolamine dehydratase 2 (PCBD2), pregnancy-specific beta-1-glycoprotein 4 (PSG4) and titin (TTN) selected to represent target genes. Using real-time quantitative RT-PCR (qRT-PCR), when CSH2 and PCBD2 (or EIF4G2, PSG4 and TTN) were silenced by RNA interference, transcriptional levels of HBV s and x genes significantly decreased (or increased) (P < 0.05). Silencing of a control gene in sperm did not significantly change transcription of HBV s and x genes (P > 0.05). This study provides the first experimental evidence that transcription of HBV genes occurs in human sperm and is regulated by host genes.
Animals ; Connectin/genetics* ; Cricetinae ; Eukaryotic Initiation Factor-4G/genetics* ; Gene Expression Regulation/genetics* ; Gene Silencing ; Growth Hormone/genetics* ; Hepatitis B Surface Antigens/genetics* ; Hepatitis B virus/genetics* ; Hepatitis B, Chronic/virology* ; Humans ; Hydro-Lyases/metabolism* ; Male ; Pregnancy-Specific beta 1-Glycoproteins/genetics* ; RNA, Viral/analysis* ; Spermatozoa/virology* ; Trans-Activators/genetics* ; Transcription, Genetic ; Transfection ; Viral Regulatory and Accessory Proteins

The newly emerged Middle East respiratory syndrome coronavirus (MERS-CoV) is a highly pathogenic respiratory virus with pathogenic mechanisms that may be driven by innate immune pathways. The goal of this study is to characterize the expression of the structural (S, E, M, N) and accessory (ORF 3, ORF 4a, ORF 4b, ORF 5) proteins of MERS-CoV and to determine whether any of these proteins acts as an interferon antagonist. Individual structural and accessory protein-coding plasmids with an N-terminal HA tag were constructed and transiently transfected into cells, and their native expression and subcellular localization were assessed using Wes tern blotting and indirect immunofluorescence. While ORF 4b demonstrated majorly nuclear localization, all of the other proteins demonstrated cytoplasmic localization. In addition, for the first time, our experiments revealed that the M, ORF 4a, ORF 4b, and ORF 5 proteins are potent interferon antagonists. Further examination revealed that the ORF 4a protein of MERS-CoV has the most potential to counteract the antiviral effects of IFN via the inhibition of both the interferon production (IFN-β promoter activity, IRF-3/7 and NF-κB activation) and ISRE promoter element signaling pathways. Together, our results provide new insights into the function and pathogenic role of the structural and accessory proteins of MERS-CoV.
Cell Line ; Coronavirus ; genetics ; pathogenicity ; Genes, Viral ; Humans ; Interferons ; antagonists & inhibitors ; Open Reading Frames ; Recombinant Proteins ; genetics ; metabolism ; Viral Matrix Proteins ; genetics ; metabolism ; Viral Regulatory and Accessory Proteins ; genetics ; metabolism ; Viral Structural Proteins ; genetics ; metabolism

BST-2 plays an important role in host innate immune response via inhibiting the release of HIV-1. HIV-1 accessory protein Vpu can interact with BST-2 through its transmembrane domains, degrade BST-2, and decrease BST-2 that are transported to the cell surface, thus anti-virus function of BST-2 is antagonized. In our study, we constructed plasmid RB connecting Rluc to the N-termimal of BST-2, and plasmid VE connecting EYFP to the C-terminal of Vpu. The two fusion proteins were co-expressed in 293 cells, and the interaction between the two proteins was detected via BRET method. And we further established a stable 293 cell line of dual-expression. By using BRET method, and the interaction between BST-2 and Vpu transmembrane domain as the target, a high-throughput screening assay was created that was expected to seek novel interaction inhibitors.
Antigens, CD ; chemistry ; genetics ; metabolism ; Cell Line ; GPI-Linked Proteins ; chemistry ; genetics ; metabolism ; HIV Infections ; genetics ; metabolism ; virology ; HIV-1 ; genetics ; metabolism ; High-Throughput Screening Assays ; methods ; Human Immunodeficiency Virus Proteins ; genetics ; metabolism ; Humans ; Protein Binding ; Protein Structure, Tertiary ; Viral Regulatory and Accessory Proteins ; genetics ; metabolism

The SAM and HD domain containing protein 1 (Sterile alpha motif domain and HD domain-containing protein 1, SAMHD1) is a putative negative regulator of the antiviral innate immune response. It can significantly increase the antiviral immune response, mediates the interferon-induced inflammatory response involved in the host foreign-virus defense system. The early studies have focused on its gene mutations associated with Aicardi-Goutières syndrome (AGS), the latest study found that SAMHD1 as a potent dGTP-stimulated triphosphohydrolase restricts HIV-1 replication by hydrolyzing the majority of cellular dNTPs, thus inhibiting reverse transcription and viral complementary DNA (cDNA) synthesis. Auxiliary gene of HIV-2 and simian immunodeficiency virus (SIVsm / mac) encoding the Vpx protein can eliminate HIV-1 restriction. In recent years, the research on SAMHD1, mores forward rapidly this paper overviews the recent research progression related to the above fields.
Animals ; Cell Line ; HIV ; metabolism ; physiology ; Humans ; Monomeric GTP-Binding Proteins ; genetics ; metabolism ; SAM Domain and HD Domain-Containing Protein 1 ; Viral Regulatory and Accessory Proteins ; metabolism

Animals ; Antigens, CD ; chemistry ; genetics ; metabolism ; Antiviral Agents ; chemistry ; metabolism ; GPI-Linked Proteins ; HIV Infections ; metabolism ; virology ; HIV-1 ; genetics ; physiology ; Human Immunodeficiency Virus Proteins ; genetics ; metabolism ; Humans ; Membrane Glycoproteins ; chemistry ; genetics ; metabolism ; Protein Binding ; Viral Regulatory and Accessory Proteins ; genetics ; metabolism ; Virus Shedding

BACKGROUNDHepatitis B virus (HBV) x protein (HBx) in HepG2 cells causes a moderate decrease in proteolysis activity of the proteasome. A highly conserved Kunitz-type serine protease inhibitor domain within 154 amino acid residues of HBx has been identified. In this study, a peptide chain derived from the Kunitz domain (PKD) was used to study its effect on the cell cycle and apoptosis of HepG2 cells, and investigated the function of PKD on the activities of proteasomes and AAA-ATPase p97, which involves in the ubiquitin-proteasome protein degradation pathway.

METHODSThe PKD peptide (Phe-Val-Leu-Gly-Gly-Cys-Arg-His-Lys) was chemically synthesized. MTT assays were used to determine the effects of PKD on HepG2 cell growth. Mouse anti-p97 antibody was developed for Western blotting to detect the expression of p97. ATPase activity of proteasomes was measured using a colorimetric assay. Peptidase activities of proteasomes were analyzed with various peptidase-specific fluorogenic peptide substrates. Flow cytometry was used to determinate cell cycle phase and apoptosis.

RESULTSViability of HepG2 cells decreased in a PKD-dose-dependent manner. Cells exhibited significant cytotoxicity in the presence of 15 mmol/L of PKD. Western blotting analysis showed that expression of p97 was suppressed in HepG2 cells treated with PKD compared to untreated cells. The ATPase activity of proteasomes from immunoprecipitates of HepG2 cells pretreated with PKD was apparently decreased. Chymotryptic activity of proteasomes in HepG2 cells was significantly inhibited by 10 mmol/L PKD; tryptic activity and peptidylglutamyl peptide hydrolase activity of proteasomes were less inhibited by PKD than chymotryptic activity. The cell cycle phase of HepG2 cells treated with PKD for 36 hours was blocked largely at the G(0)-G(1) phase, while untreated control cells were mainly in S phase. PKD also significantly induced apoptosis.

CONCLUSIONSThe peptide derived from Kunitz domain of HBx protein induces HepG2 cell growth arrest and apoptosis, which may result from down-regulation of p97 expression, and decrease of both the ATPase and chymotryptic activities of proteasomes.

Adenosine Triphosphatases ; metabolism ; Animals ; Apoptosis ; drug effects ; Blotting, Western ; Cell Cycle ; drug effects ; Cell Line, Tumor ; Enzyme Activation ; drug effects ; Humans ; Lipopeptides ; chemistry ; pharmacology ; Mice ; Nuclear Proteins ; metabolism ; Trans-Activators ; chemistry ; Viral Regulatory and Accessory Proteins ; chemistry

BACKGROUNDHepatitis B virus encoded X protein (HBx) is a trans-activating protein that may be involved in hepatocarcinogenesis, although few natural effectors of HBx that participate in this process have been identified. We screened, by comparative proteomics method, effectors of HBx associated with hepatocarcinogenesis.

METHODSHBx positive and negative HepG2 cells were constructed and expression patterns of cellular proteins were obtained by high resolution, two dimensional electrophoresis. Comprehensive analyses of proteins associated with hepatocellular carcinoma (HCC) were focused on the differently expressed proteins (more than two-fold increase or decrease, P < 0.05) from HBx positive and negative HepG2 cells. For peptide mass fingerprinting, protein spots with different intensity between HBx positive and negative HepG2 cells were directly cut out of gels and processed for matrix assisted, laser desorption/ionization, time of flight mass spectrometry and liquid chromatography-tandem mass spectrometry (LC-ESI-MS/MS) analysis.

RESULTSThe mean number of protein spots for HBx negative and HBx positive HepG2 cells were 2095 +/- 137 and 2188 +/- 105, respectively. The analysis of paired cells showed 75 spots with significant differences in expression between HBx negative and HBx positive cells: 37 spots corresponding to 32 different proteins; 25 proteins were upregulated, 7 downregulated. We found 7 proteins not previously reported differentially expressed in HBx positive HepG2 cells. Variations in protein accumulation were confirmed for four (HSP90AB1, BCL2 associated athanogene 2, nucleophosmin and chloride intracellular channel 1) by Western blotting in HBx positive HepG2 cells.

CONCLUSIONSNumerous effectors of HBx that may promote the development of HCC are identified, of which 7 are newly noted in HepG2 cells. Several of these effectors of HBx may help in elucidating the roles of HBx in hepatocarcinogenesis and diagnostics or targets for therapeutic intervention.

Blotting, Western ; Carcinoma, Hepatocellular ; genetics ; metabolism ; Cell Line, Tumor ; Electrophoresis, Gel, Two-Dimensional ; Humans ; Polymerase Chain Reaction ; Proteomics ; methods ; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization ; Trans-Activators ; genetics ; metabolism ; Viral Regulatory and Accessory Proteins ; genetics ; metabolism

Xeroderma pigmentosum group D (XPD) gene is the second subunit of basic transcript factor TFII H; it plays an important role in transcription and nucleotide excision repair. In this study, using the total RNA extracted from HeLa cells, we cloned the human full length XPD by RT-PCR and inserted it into the pEGFP-N2 plasmid vector which expressed the green fluorescence protein (GFP). Then the recombinant plasmid pEGFP-N2/XPD was transfected into the human hepatoma carcinoma cell Hep3B integrated with HBx protein,and we analysed the expression of HBx and the proliferative ability of recombinant cells. The data collected from this study could serve as a physical basis on which to further investigate the biological activities of XPD.
Cloning, Molecular ; DNA Repair ; Female ; HeLa Cells ; Humans ; Liver Neoplasms ; genetics ; Recombinant Proteins ; genetics ; metabolism ; Trans-Activators ; genetics ; Transcription Factor TFIIH ; genetics ; Transcription, Genetic ; Transfection ; Viral Regulatory and Accessory Proteins ; genetics ; Xeroderma Pigmentosum Group D Protein ; genetics ; metabolism