Endosomal sorting complex required for transport (ESCRT) system drives various cellular processes, including endosome sorting, organelle biogenesis, vesicle transport, maintenance of plasma membrane integrity, membrane fission during cytokinesis, nuclear membrane reformation after mitosis, closure of autophagic vacuoles, and enveloped virus budding. Increasing evidence suggests that the ESCRT system can be hijacked by different family viruses for their proliferation. At different stages of the virus life cycle, viruses can interfere with or exploit ESCRT-mediated physiological processes in various ways to maximize their chance of infecting the host. In addition, many retroviral and RNA viral proteins possess "late domain" motifs, which can recruit host ESCRT subunit proteins to assist in virus endocytosis, transport, replicate, budding and efflux. Therefore, the "late domain" motifs of viruses and ESCRT subunit proteins could serve as promising drug targets in antiviral therapy. This review focuses on the composition and functions of the ESCRT system, the effects of ESCRT subunits and virus "late domain" motifs on viral replication, and the antiviral effects mediated by the ESCRT system, aiming to provide a reference for the development and utilization of antiviral drugs.
Endosomal Sorting Complexes Required for Transport/metabolism* ; Viruses/metabolism* ; Protein Transport ; Virus Replication ; Endosomes/metabolism* ; Virus Release

COPI is a protein complex that transports vesicles from the Golgi complex back to endoplasmic reticulum. Many viruses such as RNA viruses, DNA viruses and retroviruses, hijack or adapt COPI related proteins including coatomer, ARF1 and GBF1 for their own benefits. Here, we summarize the current progress of the roles of COPI related proteins in virus replication.
Animals ; Coat Protein Complex I ; genetics ; metabolism ; Humans ; Virus Diseases ; genetics ; metabolism ; virology ; Virus Physiological Phenomena ; Virus Replication

Chromatin structure governs a number of cellular processes including DNA replication, transcription, and DNA repair. During DNA replication, chromatin structure including the basic repeating unit of chromatin, the nucleosome, is temporarily disrupted, and then reformed immediately after the passage of the replication fork. This coordinated process of nucleosome assembly during DNA replication is termed replication-coupled nucleosome assembly. Disruption of this process can lead to genome instability, a hallmark of cancer cells. Therefore, addressing how replication-coupled nucleosome assembly is regulated has been of great interest. Here, we review the current status of this growing field of interest, highlighting recent advances in understanding the regulation of this important process by the dynamic interplay of histone chaperones and histone modifications.
Acetylation ; Animals ; DNA Replication ; Histone Chaperones ; metabolism ; Histones ; metabolism ; Humans ; Nucleic Acid Conformation ; Nucleosomes ; metabolism ; Protein Processing, Post-Translational

In eukaryotic cells, histones are packaged into octameric core particles with DNA wrapping around to form nucleosomes, which are the basic units of chromatin (Kornberg and Thomas, 1974). Multicellular organisms utilise chromatin marks to translate one single genome into hundreds of epigenomes for their corresponding cell types. Inheritance of epigenetic status is critical for the maintenance of gene expression profile during mitotic cell divisions (Allis et al., 2006). During S phase, canonical histones are deposited onto DNA in a replication-coupled manner (Allis et al., 2006). To understand how dividing cells overcome the dilution of epigenetic marks after chromatin duplication, DNA replication coupled (RC) nucleosome assembly has been of great interest. In this review, we focus on the potential influence of RC nucleosome assembly processes on the maintenance of epigenetic status.
Animals ; Chromatin Assembly and Disassembly ; genetics ; physiology ; DNA Replication ; Epigenesis, Genetic ; Histones ; chemistry ; physiology ; Humans ; Nucleosomes ; genetics ; physiology ; Protein Structure, Quaternary

The secondary structures of hepatitis C virus (HCV) RNA and the cellular proteins that bind to them are important for modulating both translation and RNA replication. However, the sets of RNA-binding proteins involved in the regulation of HCV translation, replication and encapsidation remain unknown. Here, we identified RNA binding motif protein 24 (RBM24) as a host factor participated in HCV translation and replication. Knockdown of RBM24 reduced HCV propagation in Huh7.5.1 cells. An enhanced translation and delayed RNA synthesis during the early phase of infection was observed in RBM24 silencing cells. However, both overexpression of RBM24 and recombinant human RBM24 protein suppressed HCV IRES-mediated translation. Further analysis revealed that the assembly of the 80S ribosome on the HCV IRES was interrupted by RBM24 protein through binding to the 5'-UTR. RBM24 could also interact with HCV Core and enhance the interaction of Core and 5'-UTR, which suppresses the expression of HCV. Moreover, RBM24 enhanced the interaction between the 5'- and 3'-UTRs in the HCV genome, which probably explained its requirement in HCV genome replication. Therefore, RBM24 is a novel host factor involved in HCV replication and may function at the switch from translation to replication.
Cells, Cultured ; Hepacivirus ; genetics ; growth & development ; metabolism ; Humans ; Protein Biosynthesis ; RNA-Binding Proteins ; metabolism ; Virus Replication ; genetics

BACKGROUND: The hepatitis B virus (HBV) vaccine has been efficiently used for decades. However, hepatocellular carcinoma caused by HBV is still prevalent globally. We previously reported that interferon (IFN)-induced tripartite motif-containing 25 (TRIM25) inhibited HBV replication by increasing the IFN expression, and this study aimed to further clarify the anti-HBV mechanism of TRIM25. METHODS: The TRIM25-mediated degradation of hepatitis B virus X (HBx) protein was determined by detecting the expression of HBx in TRIM25-overexpressed or knocked-out HepG2 or HepG2-NTCP cells via Western blotting. Co-immunoprecipitation was performed to confirm the interaction between TRIM25 and HBx, and colocalization of TRIM25 and HBx was identified via immunofluorescence; HBV e-antigen and HBV surface antigen were qualified by using an enzyme-linked immunosorbent assay (ELISA) kit from Kehua Biotech. TRIM25 mRNA, pregenomic RNA (pgRNA), and HBV DNA were detected by quantitative real-time polymerase chain reaction. The retinoic acid-inducible gene I (RIG-I) and pgRNA interaction was verified by RNA-binding protein immunoprecipitation assay. RESULTS: We found that TRIM25 promoted HBx degradation, and confirmed that TRIM25 could enhance the K90-site ubiquitination of HBx as well as promote HBx degradation by the proteasome pathway. Interestingly, apart from the Really Interesting New Gene (RING) domain, the SPRY domain of TRIM25 was also indispensable for HBx degradation. In addition, we found that the expression of TRIM25 increased the recognition of HBV pgRNA by interacting with RIG-I, which further increased the IFN production, and SPRY, but not the RING domain is critical in this process. CONCLUSIONS The study found that TRIM25 interacted with HBx and promoted HBx-K90-site ubiquitination, which led to HBx degradation. On the other hand, TRIM25 may function as an adaptor, which enhanced the recognition of pgRNA by RIG-I, thereby further promoting IFN production. Our study can contribute to a better understanding of host-virus interaction.
Humans ; Hepatitis B virus ; DEAD Box Protein 58/metabolism* ; RNA ; Liver Neoplasms ; Virus Replication ; Tripartite Motif Proteins/genetics* ; Transcription Factors ; Ubiquitin-Protein Ligases/genetics*

BACKGROUNDTo determine the feasibility of inhibition of duck hepatitis B virus (DHBV) DNA replication by antisense phosphorothioate oligodeoxynucleotides corresponding to DHBV transcription region.

METHODSThe authors designed three antisense phosphorothioate oligodeoxynucleotides which correspond to DHBV PreS1,PreS2 and S antigen gene promotors respectively. The DNA replication level was detected with Southern blot method and cpm calculation.

RESULTSPrimary duck hepatocyte culture was treated with 1.5 micromol/L antisense oligodeoxynucleotides in vitro, all the antisense fragments caused a firm inhibition of viral DNA replication and the inhibition rates were 61.5%, 69.3% and 62.4%, respectively. In vivo, the animals were treated with 10 microgram/g PreS1 antigen gene promotor antisense oligodeoxynucleotides per day for 6 days and a very strong inhibition rate of 87.9% was obtained.

CONCLUSIONSThe results demonstrated the potential clinical application of antisense phosphorothioate oligodeoxynucleotides in clinics.

Animals ; DNA Replication ; drug effects ; DNA, Viral ; drug effects ; Ducks ; Hepadnaviridae Infections ; virology ; Hepatitis B Surface Antigens ; blood ; Hepatitis B Virus, Duck ; genetics ; physiology ; Hepatitis, Viral, Animal ; virology ; Oligodeoxyribonucleotides, Antisense ; pharmacology ; Protein Precursors ; blood ; Virus Replication ; drug effects

Eukaryotic DNA replication is tightly restricted to only once per cell cycle in order to maintain genome stability. Cells use multiple mechanisms to control the assembly of the prereplication complex (pre-RC), a process known as replication licensing. This review focuses on the regulation of replication licensing by posttranslational modifications of the licensing factors, including phosphorylation, ubiquitylation and acetylation. These modifications are critical in establishing the pre-RC complexes as well as preventing rereplication in each cell cycle. The relationship between rereplication and diseases, including cancer and virus infection, is discussed as well.
Acetylation ; Animals ; Cell Cycle ; DNA Replication ; genetics ; physiology ; DNA Replication Timing ; DNA, Neoplasm ; biosynthesis ; genetics ; Genomic Instability ; Host-Pathogen Interactions ; Humans ; Models, Biological ; Neoplasms ; drug therapy ; genetics ; metabolism ; Phosphorylation ; Protein Processing, Post-Translational ; Ubiquitination ; Virus Diseases ; genetics ; metabolism

Co-infection of herpes simplex virus type 1 (HSV-1) and human cytomegalovirus (HCMV) is not uncommon in immunocompromised hosts. Importantly, organ transplant recipients concurrently infected with HSV-1 and HCMV have a worse clinical outcome than recipients infected with a single virus. However, factors regulating the pathologic response in HSV-1, HCMV co-infected tissues are unclear. We investigated the potential biologic role of HCMV gene product immediate early 1 (IE1) protein in HSV-1-induced syncytial formation in U373MG cells. We utilized a co-infection model by infecting HSV-1 to U373MG cells constitutively expressing HCMV IE1 protein, UMG1-2. Syncytial formation was assessed by enumerating nuclei number per syncytium and number of syncytia. HSV-1-induced syncytial formation was enhanced after 24 hr in UMG1-2 cells compared with U373MG controls. The amplified phenotype in UMG1-2 cells was effectively suppressed by roscovitine in addition to inhibitors of viral replication. This is the first study to provide histological evidence of the contribution of HCMV IE1 protein to enhanced cytopathogenic responses in active HSV-1 infection.
Cell Line, Tumor ; Giant Cells/*virology ; Herpesvirus 1, Human/*growth & development ; Humans ; Immediate-Early Proteins/biosynthesis/*metabolism ; Protein Kinase Inhibitors/pharmacology ; Purines/pharmacology ; Transfection ; Virus Replication/drug effects

This study was performed to investigate the effects of different regions of the Autographa califor nica multiple nucleopolyhedrovirus envelope protein E25 on its trafficking into nucleus and nuclear localization in host cells and on virus replication. Fourteen recombinant bacmids, each containing an e25 mutant with substitution or insertion of egfp, in the absence or presence of the native e25, were constructed and used to transfect Sf9 cells. The E25-EGFP fusion proteins and native E25 expressed in the cells transfect ed with individual recombinant bacmid were traced by autofluorescence from EGFP or by immuno-fluorescence assays. Confocal microscopy revealed that the E25-EGFP fusion protein with the N-domain (2-45aa) of E25 substituted by EGFP only distributed in the cytoplasm in transfected cells; and the fusion protein with EGFP inserted at the laa/2aa site of E25 completely remained outside of the nucleus and resided along the nuclear membrane. The E25-EGFPs with 46-118aa of E25 substituted by EGFP or with EGFP inserted at the 118aa/119aa site were present outside, across from the nuclear membrane or in nuclear plasm in dot-like shapes. The fusion proteins with the C-domain substituted by EGFP or with EGFP inserted at the site of 45/46aa or at the C-terminal formed a condensed ring or spread throughout the nucleus, in a similar manner to the E25 distributed in the cells transfected by the e25-knockout repair bacmid. These results prove that the N-terminal domain is critical for nuclear transportation of E25 and possibly to its position on the cytoplasm membrane as well; and the sequence downstream of the N-terminal domain also affects trafficking and nuclear localization of the protein. In cells transfected with bacmids containing both the native e25 and individual e25-egfp mutants, the E25-EGFP fusion proteins co-localized with E25 individually, showing similar patterns of subcellular localization as E25 mutants in the absence of native E25 in most cases, suggesting that the E25 likely exists and functions as dimmers or polymers. Production of infectious BV was dramatically reduced and even completely eliminated in most cases, either in the absence or presence of the native e25.
Amino Acid Motifs ; Animals ; Cell Nucleus ; metabolism ; virology ; Mutation ; Nucleopolyhedrovirus ; chemistry ; genetics ; physiology ; Protein Transport ; Spodoptera ; virology ; Viral Proteins ; chemistry ; genetics ; metabolism ; Virus Release ; Virus Replication