A novel canine papillomavirus, CfPV-2, was cloned from a footpad lesion of a golden retriever. Unlike the known canine oral papillomavirus (COPV), which has a double-stranded DNA genome size of 8607 bps, the genome of CfPV-2 is 8101 bps. Some of this size difference is due to an abbreviated early-late region (ELR), which is 1200 bps shorter than that of COPV. However, CfPV-2 has other differences from COPV, including the presence of an E5 ORF between the E2 gene and the ELR and an enlarged E4 ORF (one of the largest PV E4 open reading frames). The genome of CfPV-2 shares low homology with all the other papillomaviruses and, even in the most highly conserved ORF of L1, the nucleotide sequence shares only 57% homology with COPV. Due to this highly divergent DNA sequence, CfPV-2 establishes a new PV genus, with its closest phylogenetic relatives being amongst the Xi and Gamma genuses. CfPV-2 also has unique biological features; it induces papillomas on footpads and interdigital regions which, if infection is persistent, can progress to highly metastatic squamous cell carcinoma. CfPV-2 does not induce oral papillomas in immunocompetent animals and antibodies generated against COPV and CfPV-2 are type-specific. The availability of a new canine papillomavirus with differing genetic and biological properties now makes it possible to study type-specific host immune responses, tissue tropism and the comparative analysis of viral gene functions in the dog.

Equus caballus papillomavirus type 1 (EcPV-1) was isolated from a cutaneous papilloma, the most common neoplasm in horses. The complete EcPV-1 nucleotide sequence and genomic organization were determined. Phylogenetic analysis showed that EcPV-1 is a close-to-root papillomavirus, with only distant relationships to the fibropapillomaviruses and the benign cutaneous papillomaviruses. To produce EcPV-1 virus-like particles (VLPs), the EcPV-1 L1 major capsid protein was expressed in insect cells using a recombinant baculovirus vector. The self-assembled EcPV-1 VLPs were morphologically indistinguishable from wild type papillomavirus virions. Monoclonal antibodies were developed against intact and denatured EcPV-1 VLPs. When tested by ELISA, all monoclonal antibodies produced against intact (#18) and some against denatured EcPV-1 VLPs (#16) reacted with intact EcPV-1 VLPs only, demonstrating that the VLPs carry type-specific conformational as well as linear epitopes on their surface. Recombinant EcPV-1 VLPs offer the potential of a noninfectious vaccine to prevent and eradicate equine cutaneous papillomatosis.

Fibroblast growth factors (FGFs) signal through high-affinity tyrosine kinase receptors to regulate a diverse range of cellular processes, including cell growth, differentiation and migration, as well as cell death 1 , 2 , 3 , 4 . Here we identify XFLRT3, a member of a leucine-rich-repeat transmembrane protein family, as a novel modulator of FGF signalling. XFLRT3 is co-expressed with FGFs, and its expression is both induced after activation and downregulated after inhibition of FGF signalling. In gain- and loss-of function experiments, FLRT3 and FLRT2 phenocopy FGF signalling in Xenopus laevis . XFLRT3 signalling results in phosphorylation of ERK and is blocked by MAPK phosphatase 1, but not by expression of a dominant-negative phosphatidyl inositol 3-OH kinase (PI(3)K) mutant. XFLRT3 interacts with FGF receptors (FGFRs) in co-immunoprecipitation experiments in vitro and in bioluminescence resonance energy transfer assays in vivo . The results indicate that XFLRT3 is a transmembrane modulator of FGF–MAP kinase signalling in vertebrates.

The Wnt family of secreted glycoproteins mediate cell–cell interactions during cell growth and differentiation in both embryos and adults1,2. Canonical Wnt signalling by way of the β-catenin pathway is transduced by two receptor families. Frizzled proteins and lipoprotein-receptor-related proteins 5 and 6 (LRP5/6) bind Wnts and transmit their signal by stabilizing intracellular β-catenin3,4,5,6. Wnt/β-catenin signalling is inhibited by the secreted protein Dickkopf1 (Dkk1), a member of a multigene family, which induces head formation in amphibian embryos7. Dkk1 has been shown to inhibit Wnt signalling by binding to and antagonizing LRP5/68,9,10. Here we show that the transmembrane proteins Kremen1 and Kremen2 are high-affinity Dkk1 receptors that functionally cooperate with Dkk1 to block Wnt/β-catenin signalling. Kremen2 forms a ternary complex with Dkk1 and LRP6, and induces rapid endocytosis and removal of the Wnt receptor LRP6 from the plasma membrane. The results indicate that Kremen1 and Kremen2 are components of a membrane complex modulating canonical Wnt signalling through LRP6 in vertebrates.

High-risk human papillomavirus types, especially type 16, are risk factors for cervical cancer. Preliminary studies suggest that HPV16 polymorphisms in the long control region or in the E6 gene may alter the oncogenic potential of the virus. This could partially explain why some lesions progress to cancer while others do not. A systematic study combining the long control region and E6 has not been undertaken. This prompted us to investigate the long control region and the E6 in northern European women infected with human papillomavirus 16. We identified the sequence variations of both regions and investigated the long control region promoter activity among various isolates. In addition, we correlated the distribution of long control region and E6 polymorphisms with disease status. We analyzed 45 samples from Swedish and Finnish women. The long control region and the E6 gene were sequenced after polymerase chain reaction long control region fragments of six European isolates covering the majority of polymorphisms in this region were ligated into the pALuc vector and used for luciferase assays. In European HPV16 isolates, polymorphisms in the long control region are more frequent than in the E6 gene. Nevertheless, the promoter function was slightly increased in only one of the tested European long control region variants. In addition, we found a specific European E6 variant, L83V, to be enriched in high-grade lesions and cancer rather than a specific European long control region variant. The difference in oncogenicity between European HPV16 genotypes is more probably due to an altered property of the corresponding E6 proteins rather than to an altered activity of the P97 promoter.

TT viruses have recently been reported in serum samples from varying percentages of human blood donors and in patients with chronic liver disease. However, no association with human pathology has yet been reported. In a pilot study we analysed 162 biopsy specimens from various human cancers and from colon polyps for the presence of TT virus related sequences by polymerase chain reaction using three sets of nested primers for TT virus detection. All gels were subjected to Southern blot hybridisation, and DNA from hybridising bands was cloned and sequenced. A total of 54.3% of tumour specimens contained identifiable TT virus related sequences. Specimens from hypopharynx, larynx, endometrial, ovarian and bladder cancers were 14–35% positive and gastrointestinal cancers (oesophagus, stomach, colon, rectum) and colon polyps 57–100% positive. Lung cancers (68.4%), mammary cancers (50%), multiple myelomas (85.7%) and human leukaemias (53.3%) also revealed a high prevalence of TT virus related sequences. Since normal control tissues were not available for the tumour biopsy specimens tested, these data do not permit conclusions concerning a possible causal relationship between the virus infections and carcinogenesis. Another aspect, however, deserves attention: the heterogeneity of TT virus clones obtained from the specimens tested here was striking: 66 novel sequences, probably belonging to new types were identified. Only 16 clones corresponded by more than 97% of their sequences to established prototypes. Even individual tumours commonly contained sequences substantially diverging in nucleic acid composition. Up to five different types were identified within an individual tumour. The high variability of these virus types suggests that additional primer combinations within the highly conserved region of the genome would detect a still higher rate of positive tumours.

Risk factors other than human papillomavirus (HPV) infection per se for cervical cancer development have been investigated recently. It was suggested that HPV 16 E6 variants and the p53 codon 72 arginine polymorphism could be progression markers. Indeed, it has been demonstrated that specific E6 variants and p53 arginine were both enriched in cancer. However, especially with regard to the latter, divergent results have been reported. Our aim was thus to investigate whether p53 arginine is important for cervical carcinogenesis by scaling up samples of the two European cohorts, the initial results of which were reported previously. In addition, we have assessed the occurrence of p53 codon 72 arginine, in combination with specific HPV 16 E6 genotypes. We found p53 arginine to be increased in cancer of both cohorts, consistent with our previous concept. Although specificE6 genotypes increased gradually with the severity of the lesion, p53 arginine was enriched in cancer only. Moreover, the frequency of the arginine allele was similar in groups with differentE6 genotypes. It is concluded that p53 arginine is a risk factor for cervical cancer but probably acts independently of E6 variants.

The expression of the monocyte-chemoattractant-protein-1 (MCP-1) is closely linked with a non-tumorigenic phenotype in somatic cell hybrids made between the human papillomavirus type 18 (HPV 18) positive cervical carcinoma cell line HeLa and normal human fibroblasts. In contrast, MCP-1 transcription is absent in tumorigenic segregants derived from the same hybrids or in parental HeLa cells. Selectivity of MCP-1 transcription, which is regulated at the level of initiation of transcription, is mainly based on differences in the location and extension of DNAse I-hypersensitive regions (DHSR) at both ends of the gene. While TNF-α only moderately increases the sensitivity of pre-existing 5′-DHSRs, a 3′-end DHSR became strongly induced exclusively in non-malignant hybrids. DNA sequencing showed that the 3′-DHSR coincides with an additional AP-1 site located approximately 600 bp downstream of the polyadenylation site. Analyses of AP-1 composition revealed that MCP-1 is only expressed in those cells where jun-family members were mainly heterodimerized with the fos-related protein fra-1. In contrast, in tumorigenic cells the 1 : 1 ratio between jun and fra-1 is disturbed and the MCP-1 gene is no longer expressed. Hence, alterations in the heterodimerization pattern of AP-1 and its selective accessibility to opened chromatin may represent a novel regulatory pathway in the regulation of chemokines in malignant and non-malignant HPV-positive cells.

Representational difference analysis of cDNA (cDNA-RDA) was used for a comparison of the global transcript level of tumor of the larynx and the corresponding normal epithelial tissue toward the end of detecting differentially expressed genes. Overall, some 130 gene fragments were identified. By sequence analysis and homology comparison, they could be put into several groups related to (potential) functions. Apart from genes whose overexpression was most likely a result of tumor growth or dedifferentiation of epithelial tissue, a lot of genes were isolated that play major roles in signal transduction pathways or apoptosis or act as oncogenes or tumor suppressor genes, in addition to new, entirely unknown genes. Moreover, some cDNAs of known genes were identified that derived from unconventional splicing activity or other transcript modifications. All identified fragments were arrayed on solid support and used for reverse Northern blot analyses. The use of preselected RDA fragments as targets in array-based profiling experiments circumvents many of the problems encountered when dealing with large clone libraries.

Approximately 90% of cervical carcinomas are causally linked to infections with high-risk human papillomaviruses (HPVs), whose oncogenicity has been assigned to the continued expression of two early genes, E6 and E7. Reversal of the transformed phenotype by inhibiting E6/E7 gene expression therefore provides a suitable goal for future tumor therapy. Using recombinant adeno-associated virus type 2 (AAV-2) vectors, two types of therapeutic genes were expressed in cervical carcinoma cells with the aim of suppressing the E6/E7 oncogenes: (a) antisense E6/E7 and ribozyme genes and (b) the monocyte chemoattractant protein-1 (MCP-1) gene encoding MCP-1. Previous studies have shown that the MCP-1 protein is able to indirectly repress E6/E7 gene expression and is consistently absent in tumorigenic HPV-positive cervical carcinoma cell lines. Here, the effect of these therapeutic genes on tumor formation is analyzed in nude mice after ex vivo gene transfer into a HPV16- or HPV18-positive cervical carcinoma cell line (HeLa or SiHa, respectively). Whereas AAV-2 vector-mediated transfer of antisense or even ribozyme genes did not significantly influence tumor formation from implanted SiHa cells, the transfer and expression of human MCP-1 strongly inhibited the development of tumors derived from either HeLa or SiHa cells. Similar results were also obtained after in vivo delivery of these genes into SiHa-derived tumors. This suggests that transfer of therapeutic genes mediating a systemic effect via recombinant AAV-2 vectors offers a promising approach for the development of gene therapies directed against papillomavirus-induced human cancers.

Members of the transforming growth factor-β (TGF-β) superfamily, including TGF-β, bone morphogenetic proteins (BMPs), activins and nodals, are vital for regulating growth and differentiation 1 . These growth factors transduce their signals through pairs of transmembrane type I and type II receptor kinases 2 , 3 , 4 . Here, we have cloned a transmembrane protein, BAMBI, which is related to TGF-β-family type I receptors but lacks an intracellular kinase domain. We show that BAMBI is co-expressed with the ventralizing morphogen BMP4 (refs 5 , 6 ) during Xenopus embryogenesis and that it requires BMP signalling for its expression. The protein stably associates with TGF-β-family receptors and inhibits BMP and activin as well as TGF-β signalling. Finally, we provide evidence that BAMBI's inhibitory effects are mediated by its intracellular domain, which resembles the homodimerization interface of a type I receptor and prevents the formation of receptor complexes. The results indicate that BAMBI negatively regulates TGF-β-family signalling by a regulatory mechanism involving the interaction of signalling receptors with a pseudoreceptor.

We have characterized 95% (4,404 nucleotides) of the genome of adeno-associated virus type 5 (AAV5), including part of the terminal repeats and the terminal resolution site. Our results show that AAV5 is different from all other described AAV serotypes at the nucleotide level and at the amino acid level. The sequence homology to AAV2, AAV3B, AAV4, and AAV6 at the nucleotide level is only between 54 and 56%. The positive strand contains two large open reading frames (ORFs). The left ORF encodes the nonstructural (Rep) proteins, and the right ORF encodes the structural (Cap) proteins. At the amino acid level the identities with the capsid proteins of other AAVs range between 51 and 59%, with a high degree of heterogeneity in regions which are considered to be on the exterior surface of the viral capsid. The overall identity for the nonstructural Rep proteins at the amino acid level is 54.4%. It is lowest at the C-terminal 128 amino acids (10%). There are only two instead of the common three putative Zn fingers in the Rep proteins. The Cap protein data suggest differences in capsid surfaces and raise the possibility of a host range distinct from those of other parvoviruses. This may have important implications for AAV vectors used in gene therapy.

ABSTRACT One hallmark of prion diseases is the accumulation of the abnormal isoform PrP Sc of a normal cellular glycoprotein, PrP c , which is characterized by a high content of β-sheet structures and by its partial resistance to proteinase K. It was hypothesized that the PrP region comprising amino acid residues 109 to 122 [PrP(109–122)], which spontaneously forms amyloid when it is synthesized as a peptide but which does not display significant secondary structure in the context of the full-length PrP c molecule, should play a role in promoting the conversion into PrP Sc . By using persistently scrapie-infected mouse neuroblastoma (Sc + -MNB) cells as a model system for prion replication, we set out to design dominant-negative mutants of PrP c that are capable of blocking the conversion of endogenous, wild-type PrP c into PrP Sc . We constructed a deletion mutant (PrP c Δ114–121) lacking eight codons that span most of the highly amyloidogenic part, AGAAAAGA, of PrP(109–122). Transient transfections of mammalian expression vectors encoding either wild-type PrP c or PrP c Δ114–121 into uninfected mouse neuroblastoma cells (Neuro2a) led to overexpression of the respective PrP c versions, which proved to be correctly localized on the extracellular face of the plasma membrane. Transfection of Sc + -MNB cells revealed that PrP c Δ114–121 was not a substrate for conversion into a proteinase K-resistant isoform. Furthermore, its presence led to a significant reduction in the steady-state levels of PrP Sc derived from endogenous PrP c . Thus, we showed that the presence of amino acids 114 to 121 of mouse PrP c plays an important role in the conversion process of PrP c into PrP Sc and that a deletion mutant lacking these codons indeed behaves as a dominant-negative mutant with respect to PrP Sc accumulation. This mechanism could form a basis for a new gene therapy and/or a prevention concept for prion diseases.

The Spemann organizer in amphibian embryos is a tissue with potent head-inducing activity, the molecular nature of which is unresolved. Here we describe dickkopf-1 (dkk-1), which encodes Dkk-1, a secreted inducer of Spemann's organizer in Xenopus and a member of a new protein family. Injections of mRNA and antibody Indicate that dkk-1 is sufficient and necessary to cause head induction. dkk-1 is a potent antagonist of Wnt signalling, suggesting that dkk genes encode a family of secreted Wnt inhibitors.