The Nucleotide Sequence and Genome Organization of Bovine Papillomavirus Type 4

The L-X-C-X-E pRB-binding motif of papillomavirus (PV) E7 proteins has been implicated in the immortalization and transformation of the host cell. However, sequencing of the complete genomes of bovine papillomavirus type 3 (BPV-3), bovine papillomavirus type 5 (BPV-5), equine papillomavirus (EQPV) and reindeer (Rangifer tarandus) papillomavirus (RPV) supports the notion that the pRB-binding motif is not ubiquitous among E7 proteins in the PV proteome. Key among the animal groups that lack the pRB-binding domain are the artiodactyl PVs, including European elk PV (EEPV), deer PV (DPV), reindeer PV (RPV), ovine PVs types 1 and 2 (OvPV-1 and -2) and bovine PVs 1, 2 and 5 (BPV-1, -2 and -5). Whereas the presence of the pRB-binding domain is normally associated with papillomas, the artiodactyl PVs are marked by the development of fibropapillomas on infection. Previous studies emphasized the role of E5 in the pathogenic mechanism of fibropapilloma development, but correlation between the lack of an E7 pRB-binding domain and the unique pathology of the artiodactyl PVs suggests a more complicated mechanism and an early evolutionary divergence from a pRB-binding ancestor. INTRODUCTIONPapillomaviruses (PVs) are highly species-specific pathogens. They form a heterogeneous group of closed-circular, double-stranded DNA viruses measuring about 8 kb in size (Sundberg et al., 1996). Most PVs target the basal cells of dermal or mucosal epithelia (Cheville & Olson, 1964), and infection has been implicated in both benign and malignant lesions of epithelia in a broad range of animals (Sundberg & O'Banion, 1989). Though almost all known human PVs (HPVs) infect dermal or mucosal surfaces, in some animal PVs, most notably in the artiodactyl ruminant PVs, fibroblasts appear to be the primary target cells (Sundberg et al., 1985). However, regardless of species, infection generally manifests as a papilloma or fibropapilloma, and follows a cytopathic mechanism of cell proliferation (Sundberg et al., 1996). Historically, PVs had been classified according to their tissue tropism, and this grouping was supported by later phylogenetic analysis of PV sequence data (Chan et al., 1995;de Villiers, 2001;Myers, 1994). PV phylogenies typically subdivide into mucosal/genital HPVs, cutaneous EV HPVs and three main animal PV clades: the artiodactyl ruminant PVs, the distant avian PV group and a group containing canine, feline, rabbit and rodent PV types. However, sequence analysis has highlighted some significant exceptions. BPV-3, BPV-4 and BPV-6 do not group with the artiodactyl PVs, but instead form an isolated taxon (Jarrett et al., 1984), and HPV-1, HPV-41 and HPV-63 are most closely related to the canine and feline PVs, sharing little similarity to HPVs in either the mucosal or the cutaneous groups (Egawa et al., 1993).Although most work in the area has focused on HPVs, an ever-increasing number of animal PV isolates have been sequenced. These animal PVs share key clinical features of GenBank data deposited: bovine papillomavirus 3, AF486184; bo...

Section: Resultsmentioning

confidence: 99%

Lack of the canonical pRB-binding domain in the E7 ORF of artiodactyl papillomaviruses is associated with the development of fibropapillomas

Narechania

Terai

Chen

et al. 2004

“…Comparison of the 754 nucleotide (nO sequence of cDNA 7El 1 with the BPV-4 genomic sequence (Patel et al, 1987) revealed two regions of homology. The 5' end of the cDNA was located at nt 943, but contiguous homology with the viral genome ended at nt 1016, a consensus splice donor site (Breathnach & Chambon, 1981).…”

Section: Sequence Analysis Of Cdna 7ellmentioning

confidence: 99%

“…The major transcripts are thought to express the E4 protein of BPV-4, while the minor species may encode transcription-regulating proteins. The nucleotide sequences of BPV-4 cDNAs precisely located the early polyadenylation site, and in addition led to alterations in the previously reported genomic sequence and organization of BPV-4 (Patel et al, 1987). Two new promoters were identified and a candidate sequence for the control of transcription from the heterogeneous late RNA start site of papillomaviruses is proposed.…”

Section: Introductionmentioning

confidence: 99%

Mapping of Two Novel Transcripts of Bovine Papillomavirus Type 4

1988

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SUMMARYA cDNA library was synthesized using RNA from bovine papillomavirus type 4 (BPV-4)-induced papillomas. The major viral transcript was characterized by sequencing of its cDNA, primer extension mapping and S 1 nuclease protection studies. The transcript initiates at multiple sites between nucleotide (nt) 777 and nt 902, contains a splice junction between nt 1016 and nt 3376 and terminates at nt 4034, using the early polyadenylation signal at nt 4009. Sequencing of viral cDNAs and mRNA revealed deviations from the reported genomic sequence between nt 3412 and nt 3460. These resulted in a temporary frameshift, abolished the translation termination codon of the E5a open reading flame (ORF), and introduced a new termination codon in the E40RF. The new uninterrupted E50RF was found to have greater homology to the E40RFs of other papillomaviruses than to their E50RFs. The E50RF of BPV-4 is joined to a five codon ORF in the leader exon of the major transcript, in the same way as the E40RF in the major transcripts of BPV-1 and human papillomavirus type 11. On this basis, it has been redesignated E4, and the viral genomic sequence revised. Two novel transcriptional promoters of BPV-4 were defined: a putative controller of the multiple major RNA start sites around nt 870 and a minor TATA box at nt 691. In addition, minor early region transcripts were mapped which initiate between nt 3071 and nt 3152. None of these transcripts utilizes the splice site at nt 3376. These messages may express E2-encoded functions.

“…A GC box, present within the limits of NR2 defined by the deletion analysis, was initially identified as a potential binding site for the trans-activator Spl (Patel et al, 1987). However, Kageyama & Pastan (1989) have identified a transcriptional repressor, GCF, in human cells which binds to GC-rich sequences, the consensus binding sequence being GCGGGGC.…”

Section: Discussionmentioning

confidence: 99%

“…The viral genome is 7265 nucleotides long and can be roughly divided into two sections, encoding the early and late viral proteins. Upstream of the early region is a long control region (LCR) which contains potential binding sites for several factors, including NF 1, Sp 1 and the viral trans-activator E2 (Patel et al, 1987). By analogy with BPV-1, which is able to transform mouse cells in vitro although it does not cause cancer in vivo (Broker & Botchan, 1986), both positive and negative regulation of the BPV-4 LCR might be expected to occur via the action of full-length (trans-activator) and short (repressor) E2 molecules binding at the E2 sites (Lambert et al, 1989).…”

Section: Introductionmentioning

confidence: 99%

Positive and negative E2-independent regulatory elements in the long control region of bovine papillomavirus type 4

1991

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The long control region (LCR) of bovine papillomavirus type 4 demonstrated enhancer activity when cloned upstream of a bacterial chloramphenicol acetyltransferase reporter gene under thymidine kinase promoter control. Deletion analysis of the LCR revealed the presence of several positive and negative control elements, all of which could function independently of the viral E2 trans-activator. Each of the three positive elements present appeared to be paired with a negative element which modulated its activity. DNase I footprinting was used to identify protein binding sites within the LCR, which might represent these control elements. The results suggest a highly complex and finely tuned control of viral gene expression.