A Laterally Transferred Viral Gene Modifies Aphid Wing Plasticity.

Organisms often respond to changing environments by altering development of particular traits. These plastic traits exhibit genetic variation; i.e., genotypes respond differently to the same environmental cues. Theoretical studies have demonstrated the importance of this variation, which is targeted by natural selection, in adapting plastic responses to maximize fitness [1, 2]. However, little is known about the underlying genetic mechanisms. We identify two laterally transferred genes that contribute to variation in a classic example of phenotypic plasticity: the pea aphid's ability to produce winged offspring in response to crowding. We discovered that aphid genotypes vary extensively for this trait and that aphid genes of viral origin are upregulated in response to crowding solely in highly inducible genotypes. We knocked down expression of these genes to demonstrate their functional role in wing plasticity. Through phylogenetic analysis, we found that these genes likely originated from a virus that infects rosy apple aphids and causes their hosts to produce winged offspring [3]. The function of these genes has therefore been retained following transfer to pea aphids. Our results uncover a novel role for co-opted viral genes, demonstrating that they are used to modulate ecologically relevant, plastic phenotypes. Our findings also address a critical question about the evolution of environmentally sensitive traits: whether the genes that control the expression of plastic traits also underlie variation in plasticity. The genes we identify originated from outside aphids themselves, and thus, our work shows that genes formerly unrelated to plasticity can fine-tune the strength of plastic responses to the environment.

Interferon-γ Promotes Inflammation and Development of T-Cell Lymphoma in HTLV-1 bZIP Factor Transgenic Mice.

Human T-cell leukemia virus type 1 (HTLV-1) is an etiological agent of several inflammatory diseases and a T-cell malignancy, adult T-cell leukemia (ATL). HTLV-1 bZIP factor (HBZ) is the only viral gene that is constitutively expressed in HTLV-1-infected cells, and it has multiple functions on T-cell signaling pathways. HBZ has important roles in HTLV-1-mediated pathogenesis, since HBZ transgenic (HBZ-Tg) mice develop systemic inflammation and T-cell lymphomas, which are similar phenotypes to HTLV-1-associated diseases. We showed previously that in HBZ-Tg mice, HBZ causes unstable Foxp3 expression, leading to an increase in regulatory T cells (Tregs) and the consequent induction of IFN-γ-producing cells, which in turn leads to the development of inflammation in the mice. In this study, we show that the severity of inflammation is correlated with the development of lymphomas in HBZ-Tg mice, suggesting that HBZ-mediated inflammation is closely linked to oncogenesis in CD4+ T cells. In addition, we found that IFN-γ-producing cells enhance HBZ-mediated inflammation, since knocking out IFN-γ significantly reduced the incidence of dermatitis as well as lymphoma. Recent studies show the critical roles of the intestinal microbiota in the development of Tregs in vivo. We found that even germ-free HBZ-Tg mice still had an increased number of Tregs and IFN-γ-producing cells, and developed dermatitis, indicating that an intrinsic activity of HBZ evokes aberrant T-cell differentiation and consequently causes inflammation. These results show that immunomodulation by HBZ is implicated in both inflammation and oncogenesis, and suggest a causal connection between HTLV-1-associated inflammation and ATL.

The Epstein-Barr virus encoded BART miRNAs potentiate tumor growth in vivo.

The human herpes virus Epstein-Barr virus (EBV) latently infects and drives the proliferation of B lymphocytes in vitro and is associated with several forms of lymphoma and carcinoma in vivo. The virus encodes ~30 miRNAs in the BART region, the function of most of which remains elusive. Here we have used a new mouse xenograft model of EBV driven carcinomagenesis to demonstrate that the BART miRNAs potentiate tumor growth and development in vivo. No effect was seen on invasion or metastasis, and the growth promoting activity was not seen in vitro. In vivo tumor growth was not associated with the expression of specific BART miRNAs but with up regulation of all the BART miRNAs, consistent with previous observations that all the BART miRNAs are highly expressed in all of the EBV associated cancers. Based on these observations, we suggest that deregulated expression of the BART miRNAs potentiates tumor growth and represents a general mechanism behind EBV associated oncogenesis.

[The construction of a novel recombinant virus Δ67R-RGV and preliminary analyses the function of the 67R gene].

The Rana grylio virus (RGV) is a member of the genus Ranavirus. It belongs to the family Iridoviridae, and contains the gene 67R encoding dUTPase. In order to investigate the function of 67R in the replication and infection of RGV, we constructed Δ67R-RGV, a recombinant virus with deletion of 67R. First, we constructed the plasmid pGL3-67RL-p50-EGFP-67RR which carried an enhanced green fluorescence gene (EGFP) as a selectable marker. After homologous recombination between pGL3-67RL-p50-EG- FP-67RR and the RGV genome, Epithelioma papulosum cyprini (EPC) cells were infected with the resulting mixture. Through ten successive rounds of plaque isolation via EGFP selection, all plaques emitted green fluorescence, and finally Δ67R-RGV was generated. Total DNA of Δ67R-RGV infected cells was extracted for PCR analyses. Simulateously, mock infected and wild-type RGV (wt-RGV) infected cells were used as a comparison. Results showed that 67R could be detected in wt-RGV infected cells, but that only the EGFP gene was detected in Δ67R-RGV infected cells. Furthermore, one-step growth curves of wt-RGV and Δ67R-RGV were similar. Therefore, 67R and its encoding product dUTPase might not be essential for the growth of RGV. These results suggest that, homologous recombination and recombinant rana- virus could be used to study the gene function of viruses in aquatic animals.

Abortive lytic reactivation of KSHV in CBF1/CSL deficient human B cell lines.

Since Kaposi's sarcoma associated herpesvirus (KSHV) establishes a persistent infection in human B cells, B cells are a critical compartment for viral pathogenesis. RTA, the replication and transcription activator of KSHV, can either directly bind to DNA or use cellular DNA binding factors including CBF1/CSL as DNA adaptors. In addition, the viral factors LANA1 and vIRF4 are known to bind to CBF1/CSL and modulate RTA activity. To analyze the contribution of CBF1/CSL to reactivation in human B cells, we have successfully infected DG75 and DG75 CBF1/CSL knock-out cell lines with recombinant KSHV.219 and selected for viral maintenance by selective medium. Both lines maintained the virus irrespective of their CBF1/CSL status. Viral reactivation could be initiated in both B cell lines but viral genome replication was attenuated in CBF1/CSL deficient lines, which also failed to produce detectable levels of infectious virus. Induction of immediate early, early and late viral genes was impaired in CBF1/CSL deficient cells at multiple stages of the reactivation process but could be restored to wild-type levels by reintroduction of CBF1/CSL. To identify additional viral RTA target genes, which are directly controlled by CBF1/CSL, we analyzed promoters of a selected subset of viral genes. We show that the induction of the late viral genes ORF29a and ORF65 by RTA is strongly enhanced by CBF1/CSL. Orthologs of ORF29a in other herpesviruses are part of the terminase complex required for viral packaging. ORF65 encodes the small capsid protein essential for capsid shell assembly. Our study demonstrates for the first time that in human B cells viral replication can be initiated in the absence of CBF1/CSL but the reactivation process is severely attenuated at all stages and does not lead to virion production. Thus, CBF1/CSL acts as a global hub which is used by the virus to coordinate the lytic cascade.

Transcriptional activation of the adenoviral genome is mediated by capsid protein VI.

Gene expression of DNA viruses requires nuclear import of the viral genome. Human Adenoviruses (Ads), like most DNA viruses, encode factors within early transcription units promoting their own gene expression and counteracting cellular antiviral defense mechanisms. The cellular transcriptional repressor Daxx prevents viral gene expression through the assembly of repressive chromatin remodeling complexes targeting incoming viral genomes. However, it has remained unclear how initial transcriptional activation of the adenoviral genome is achieved. Here we show that Daxx mediated repression of the immediate early Ad E1A promoter is efficiently counteracted by the capsid protein VI. This requires a conserved PPxY motif in protein VI. Capsid proteins from other DNA viruses were also shown to activate the Ad E1A promoter independent of Ad gene expression and support virus replication. Our results show how Ad entry is connected to transcriptional activation of their genome in the nucleus. Our data further suggest a common principle for genome activation of DNA viruses by counteracting Daxx related repressive mechanisms through virion proteins.

Giant DNA virus mimivirus encodes pathway for biosynthesis of unusual sugar 4-amino-4,6-dideoxy-D-glucose (Viosamine).

Mimivirus is one the largest DNA virus identified so far, infecting several Acanthamoeba species. Analysis of its genome revealed the presence of a nine-gene cluster containing genes potentially involved in glycan formation. All of these genes are co-expressed at late stages of infection, suggesting their role in the formation of the long fibers covering the viral surface. Among them, we identified the L136 gene as a pyridoxal phosphate-dependent sugar aminotransferase. This enzyme was shown to catalyze the formation of UDP-4-amino-4,6-dideoxy-D-glucose (UDP-viosamine) from UDP-4-keto-6-deoxy-D-glucose, a key compound involved also in the biosynthesis of L-rhamnose. This finding further supports the hypothesis that Mimivirus encodes a glycosylation system that is completely independent of the amoebal host. Viosamine, together with rhamnose, (N-acetyl)glucosamine, and glucose, was found as a major component of the viral glycans. Most of the sugars were associated with the fibers, confirming a capsular-like nature of the viral surface. Phylogenetic analysis clearly indicated that L136 was not a recent acquisition from bacteria through horizontal gene transfer, but it was acquired very early during evolution. Implications for the origin of the glycosylation machinery in giant DNA virus are also discussed.

The HBx protein of hepatitis B virus regulates the expression, intracellular distribution and functions of ribosomal protein S27a.

The pleiotropic HBx protein of hepatitis B virus is linked functionally to the development of hepatocellular carcinoma (HCC) via effectors and signalling pathways of the host. To identify such effectors in a macrocarcinogenic environment, a PCR-based cDNA subtraction analysis was carried out in the X15-myc oncomouse model of HCC. Altogether, 19 categories of genes, mainly involved in protein biosynthesis and the electron-transport chain, were found to be upregulated in the liver of these mice. Ribosomal protein S27a (RPS27a), which is a natural fusion protein of N-terminal ubiquitin and C-terminal extension protein (CEP), topped the list of expressed genes, with >20-fold higher expression compared with its normal level. Sustained and elevated expression of RPS27a in the mouse liver and its moderate expression in cell culture in the presence of HBx suggested an indirect role of RPS27a in hepatocarcinogenesis. Nevertheless, a remarkable change in the intracellular distribution of ubiquitin from cytoplasm to late-endosomal lysosomes, and of CEP from nucleoli to the perinucleolar region/nuclear foci, was observed in the presence of HBx. RPS27a accelerated the progression of the cell cycle and cooperated with HBx in this process. Further, the knockdown of RPS27a expression by RNA interference in an HBx microenvironment led to retarded cell-cycle progression and reduced cell size. Thus, these results suggest strongly that RPS27a could be an effector of HBx-mediated hepatocarcinogenesis.

HCV and HCC: clinical update and a review of HCC-associated viral mutations in the core gene.

Hepatocellular carcinoma (HCC) is a common cause of cancer-related mortality. The worldwide incidence of HCC and the hepatitis C virus (HCV) has increased over several decades suggesting an etiologic link. Progress has been made recently in several fields related specifically to HCV and HCC. The epidemiology has been better characterized, surveillance and treatment programs have been instituted, and data have emerged detailing the effect of other risk factors for HCC in patients with HCV. Studies of HCV-related HCC suggest differences in oncogenic potential according to genotype and mutations in the viral sequence. These same mutations are associated with interferon treatment failure, insulin resistance, and expression of HCV minicore proteins. These viral mutations provide a focus for investigations into the molecular basis of HCV-related oncogenesis, which may lead to improved diagnostic tests for early (curable) HCC and to interventions to prevent, and/or greatly retard, the oncogenic process.

Coordination of KSHV latent and lytic gene control by CTCF-cohesin mediated chromosome conformation.

Herpesvirus persistence requires a dynamic balance between latent and lytic cycle gene expression, but how this balance is maintained remains enigmatic. We have previously shown that the Kaposi's Sarcoma-Associated Herpesvirus (KSHV) major latency transcripts encoding LANA, vCyclin, vFLIP, v-miRNAs, and Kaposin are regulated, in part, by a chromatin organizing element that binds CTCF and cohesins. Using viral genome-wide chromatin conformation capture (3C) methods, we now show that KSHV latency control region is physically linked to the promoter regulatory region for ORF50, which encodes the KSHV immediate early protein RTA. Other linkages were also observed, including an interaction between the 5' and 3' end of the latency transcription cluster. Mutation of the CTCF-cohesin binding site reduced or eliminated the chromatin conformation linkages, and deregulated viral transcription and genome copy number control. siRNA depletion of CTCF or cohesin subunits also disrupted chromosomal linkages and deregulated viral latent and lytic gene transcription. Furthermore, the linkage between the latent and lytic control region was subject to cell cycle fluctuation and disrupted during lytic cycle reactivation, suggesting that these interactions are dynamic and regulatory. Our findings indicate that KSHV genomes are organized into chromatin loops mediated by CTCF and cohesin interactions, and that these inter-chromosomal linkages coordinate latent and lytic gene control.

Krüppel-like factor 15 activates hepatitis B virus gene expression and replication.

UNLABELLED: Hepatitis B virus (HBV) is a small DNA virus that requires cellular transcription factors for the expression of its genes. To understand the molecular mechanisms that regulate HBV gene expression, we conducted a yeast one-hybrid screen to identify novel cellular transcription factors that may control HBV gene expression. Here, we demonstrate that Krüppel-like factor 15 (KLF15), a liver-enriched transcription factor, can robustly activate HBV surface and core promoters. Mutations in the putative KLF15 binding site in the HBV core promoter abolished the ability of KLF15 to activate the core promoter in luciferase assays. Furthermore, the overexpression of KLF15 stimulated the expression of HBV surface antigen (HBsAg) and the core protein and enhanced viral replication. Conversely, small interfering RNA knockdown of the endogenous KLF15 in Huh7 cells resulted in a reduction in HBV surface- and core-promoter activities. In electrophoretic mobility shift and chromatin immunoprecipitation assays, KLF15 binds to DNA probes derived from the core promoter and the surface promoter. Introduction of an expression vector for KLF15 short hairpin RNA, together with the HBV genome into the mouse liver using hydrodynamic injection, resulted in a significant reduction in viral gene expression and DNA replication. Additionally, mutations in the KLF15 response element in the HBV core promoter significantly reduced viral DNA levels in the mouse serum. CONCLUSION: KLF15 is a novel transcriptional activator for HBV core and surface promoters. It is possible that KLF15 may serve as a potential therapeutic target to reduce HBV gene expression and viral replication.

P-TEFb kinase complex phosphorylates histone H1 to regulate expression of cellular and HIV-1 genes.

Transcription of HIV-1 genes depends on the RNA polymerase II kinase and elongation factor positive transcription elongation factor b (P-TEFb), the complex of cyclin T1 and CDK9. Recent evidence suggests that regulation of transcription by P-TEFb involves chromatin binding and modifying factors. To determine how P-TEFb may connect chromatin remodeling to transcription, we investigated the relationship between P-TEFb and histone H1. We identify histone H1 as a substrate for P-TEFb involved in cellular and HIV-1 transcription. We show that P-TEFb interacts with H1 and that P-TEFb inhibition by RNAi, flavopiridol, or dominant negative CDK9 expression correlates with loss of phosphorylation and mobility of H1 in vivo. Importantly, P-TEFb directs H1 phosphorylation in response to wild-type HIV-1 infection, but not Tat-mutant HIV-1 infection. Our results show that P-TEFb phosphorylates histone H1 at a specific C-terminal phosphorylation site. Expression of a mutant H1.1 that cannot be phosphorylated by P-TEFb also disrupts Tat transactivation in an HIV reporter cell line as well as transcription of the c-fos and hsp70 genes in HeLa cells. We identify histone H1 as a novel P-TEFb substrate, and our results suggest new roles for P-TEFb in both cellular and HIV-1 transcription.

Expression of papillomavirus L1 proteins regulated by authentic gene codon usage is favoured in G2/M-like cells in differentiating keratinocytes.

We investigated whether differentiation-dependent expression of papillomavirus (PV) L1 genes is influenced by the cell cycle state in keratinocytes (KCs) grown in vitro or in vivo. In primary keratinocytes, flow cytometry revealed a clear shift from predominantly G0/G1 to G2/M cells from day 1 to day 7, with a three-fold increase in G2/M-like cells in day 7 keratinocytes that showed approximately 50% of the cells expressed a terminal differentiation marker involucrin. The correlation between the levels of the L1 proteins expressed from authentic (Nat) L1 genes of HPV6b and BPV1 and the frequencies of the G2/M-like KCs was significantly positive, while in contrast, a significantly negative correlation in the levels of L1 proteins expressed from codon-modified (Mod) L1 genes of HPV6b and BPV1 with the frequencies of the G2/M-like KCs was observed. Experiments using cell cycle arrest reagents (all-trans retinoic acid (RA) and colchicine) confirmed that L1 proteins expressed from PV Nat L1 genes were facilitated in G2/M-like KCs upon differentiation. Using immunofluorescence microscopy, it appears that L1 proteins from PV Nat L1 genes were co-expressed with cyclin B1, while the L1 proteins expressed from PV Mod L1 genes were preferentially associated with cyclin D2 in KCs in vitro and in mouse skin. Our results demonstrate that (1) expression of the L1 proteins from Nat L1 genes of HPV6b and BPV1 that have strong codon usage bias with A or T at codon third position dependent on KC differentiation is favoured by the G2/M-like environment and (2) codon modifications can alter the cell differentiation-dependent and cell cycle-associated patterns of expression of the PV L1 proteins in KCs.

Characterization of the rhesus fibromatosis herpesvirus MARCH family member rfK3.

Retroperitoneal fibromatosis-associated herpesvirus (RFHV) is a gamma-herpesvirus of macaques that is closely related to Kaposi's sarcoma-associated herpesvirus (KSHV). Herein, we present characterization of the K3 gene from RFHV, a homologue of the KSHV K3 and K5 genes. Like the KSHV proteins, kK3 and kK5, the rfK3 protein decreases cell surface MHC I levels. Similar to kK5, rfK3 also modulates ICAM-1, but not another kK5 target, B7.2. Inhibitors of dynamin or mutations in the rfK3 RING-CH E3 ubiquitin ligase domain block cellular target regulation, implicating a ubiquitin-dependent, endocytosis-mediated mechanism for target down regulation and degradation. Overall, this manuscript presents the first characterization of a non-human primate virus MARCH family E3 ubiquitin ligase contributing important information about the evolution of immune avoidance strategies in primate viruses and paving the way for an animal model examining the importance of kK3 and kK5 in vivo.

Identification of a Hyphantria cunea nucleopolyhedrovirus (NPV) gene that is involved in global protein synthesis shutdown and restricted Bombyx mori NPV multiplication in a B. mori cell line.

We previously demonstrated that Bombyx mori nucleopolyhedrovirus (BmNPV) multiplication is restricted in permissive BmN-4 cells upon coinfection with Hyphantria cunea NPV (HycuNPV). Here, we show that HycuNPV-encoded hycu-ep32 gene is responsible for the restricted BmNPV multiplication in HycuNPV-coinfected BmN-4 cells. The only homologue for hycu-ep32 is in Orgyia pseudotsugata NPV. hycu-ep32 could encode a polypeptide of 312 amino acids, and it contains no characteristic domains or motifs to suggest its possible functions. hycu-ep32 is an early gene, and Hycu-EP32 expression reaches a maximum by 6 h postinfection. hycu-ep32-defective HycuNPV, vHycuDeltaep32, was generated, indicating that hycu-ep32 is nonessential in permissive SpIm cells. In BmN-4 cells, HycuNPV infection resulted in a severe global protein synthesis shutdown, while vHycuDeltaep32 did not cause any specific protein synthesis shutdown. These results indicate that the restriction of BmNPV multiplication by HycuNPV is caused by a global protein synthesis shutdown induced by hycu-ep32 upon coinfection with HycuNPV.

The highly attenuated oncolytic recombinant vaccinia virus GLV-1h68: comparative genomic features and the contribution of F14.5L inactivation.

As a new anticancer treatment option, vaccinia virus (VACV) has shown remarkable antitumor activities (oncolysis) in preclinical studies, but potential infection of other organs remains a safety concern. We present here genome comparisons between the de novo sequence of GLV-1h68, a recombinant VACV, and other VACVs. The identified differences in open reading frames (ORFs) include genes encoding host-range selection, virulence and immune modulation proteins, e.g., ankyrin-like proteins, serine proteinase inhibitor SPI-2/CrmA, tumor necrosis factor (TNF) receptor homolog CrmC, semaphorin-like and interleukin-1 receptor homolog proteins. Phylogenetic analyses indicate that GLV-1h68 is closest to Lister strains but has lost several ORFs present in its parental LIVP strain, including genes encoding CrmE and a viral Golgi anti-apoptotic protein, v-GAAP. The reduced pathogenicity of GLV-1h68 is confirmed in male mice bearing C6 rat glioma and in immunocompetent mice bearing B16-F10 murine melanoma. The contribution of foreign gene expression cassettes in the F14.5L, J2R and A56R loci is analyzed, in particular the contribution of F14.5L inactivation to the reduced virulence is demonstrated by comparing the virulence of GLV-1h68 with its F14.5L-null and revertant viruses. GLV-1h68 is a promising engineered VACV variant for anticancer therapy with tumor-specific replication, reduced pathogenicity and benign tissue tropism.

The genome of human parvovirus b19 can replicate in nonpermissive cells with the help of adenovirus genes and produces infectious virus.

Human parvovirus B19 (B19V) is a member of the genus Erythrovirus in the family Parvoviridae. In vitro, autonomous B19V replication is limited to human erythroid progenitor cells and in a small number of erythropoietin-dependent human megakaryoblastoid and erythroid leukemic cell lines. Here we report that the failure of B19V DNA replication in nonpermissive 293 cells can be overcome by adenovirus infection. More specifically, the replication of B19V DNA in the 293 cells and the production of infectious progeny virus were made possible by the presence of the adenovirus E2a, E4orf6, and VA RNA genes that emerged during the transfection of the pHelper plasmid. Using this replication system, we identified the terminal resolution site and the nonstructural protein 1 (NS1) binding site on the right terminal palindrome of the viral genome, which is composed of a minimal origin of replication spanning 67 nucleotides. Plasmids or DNA fragments containing an NS1 expression cassette and this minimal origin were able to replicate in both pHelper-transfected 293 cells and B19V-semipermissive UT7/Epo-S1 cells. Our results have important implications for our understanding of native B19V infection.

A technique of segment expression and RNA interference (SERI) reveals a specific physiological function of a cysteine-rich protein gene encoded in cotesia plutellae bracovirus.

As a provirus, polydnavirus has a segmented DNA genome on chromosome(s) of host wasp. It contains several genes in each segment that presumably play critical roles in regulating physiological processes of target insect parasitized by the wasp. A cysteine-rich protein 1 (CRP1) is present in the polydnavirus Cotesia plutellae bracovirus (CpBV) genome, but its expression and physiological function in Plutella xylostella parasitized by the viral host C. plutellae is not known. This CpBV-CRP1 encoding 189 amino acids with a putative signal peptide (20 residues) was persistently expressed in parasitized P. xylostella with gradual decrease at the late parasitization period. Expression of CpBV-CRP1 was tissue-specific in the fat body/epidermis and hemocyte, but not in the gut. Its physiological function was analyzed by inducing transient expression of a CpBV segment containing CpBV-CRP1 and its promoter, which caused significant reduction in hemocyte -spreading and delayed larval development. When the treated larvae were co-injected with double-stranded RNA of CpBV-CRP1, the expression of CpBV-CRP1 disappeared,whereas other genes encoded in the CpBV segment was expressed. These co-injected larvae significantly recovered the hemocyte-spreading capacity and larval development rate. This study reports that CpBV-CRP1 is expressed in P.xylostella parasitized by C.plutellae and its physiological function is to alter the host immune and developmental processes.

West Nile virus genome amplification requires the functional activities of the proteasome.

The lifecycle of intracellular pathogens, especially viruses, is intimately tied to the macromolecular synthetic processes of their host cell. In the case of positive-stranded RNA viruses, the ability to translate and, thus, replicate their infecting genome is dependent upon hijacking host proteins. To identify proteins that participate in West Nile virus (WNV) replication, we tested the ability of siRNAs designed to knock-down the expression of a large subset of human genes to interfere with replication of WNV replicons. Here we report that multiple siRNAs for proteasome subunits interfered with WNV genome amplification. Specificity of the interference was shown by demonstrating that silencing proteasome subunits did not interfere with Venezuelan equine encephalitis virus replicons. Drugs that blocked proteasome activity were potent inhibitors of WNV genome amplification even if cells were treated 12 h after infection, indicating that the proteasome is required at a post-entry stage(s) of the WNV infection cycle.

The human papillomavirus type 8 E2 gene encodes a transforming activity sufficient for skin tumor formation in transgenic mice.

Infections with beta-genus human papillomaviruses (HPVs) have been associated with nonmelanoma skin cancers, particularly in immunocompromised patients and individuals with a rare genetic disease, epidermodysplasia verruciformis (EV). Using a transgenic mouse model, Herbert Pfister's group determined that expression of the HPV8 E2 gene results in skin cancer development and that this process is greatly accelerated by UV irradiation (Pfefferle et al., 2008, this issue).