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Jareborg N, Alderborn A, Burnett S. Identification and genetic definition of a bovine papillomavirus type 1 E7 protein and absence of a low-copy-number phenotype exhibited by E5, E6, or E7 viral mutants. J Virol 1992; 66:4957-65. [PMID: 1321280 PMCID: PMC241343 DOI: 10.1128/jvi.66.8.4957-4965.1992] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The bovine papillomavirus type 1 (BPV-1) genome replicates as a multiple-copy plasmid in murine C127 cells transformed to neoplasia by virus infection or by transfection with BPV-1 DNA. It was reported previously that BPV-1 genomes harboring frameshift mutations in the E6 or E7 open reading frame (ORF) replicated in C127 cells transformed by these mutants at a low copy number. Furthermore, the characterization of a BPV-1 mRNA in which the E6 and E7 ORFs were spliced together in frame has led to the assumption that an E6/7 fusion protein is expressed in virus-transformed C127 cells. To define the number and nature of the E6 and E7 gene products expressed in BPV-1-transformed cells, we performed immunoprecipitation experiments with antisera raised to bacterially expressed BPV-1 E6 and E7 fusion proteins. By employing cell culture conditions which induce BPV-1 E2 transactivator expression and viral early region transcription in virus-transformed C127 cell lines, we detected a single immunoprecipitated E6 protein species with an apparent molecular mass of 17 kDa and a single E7 protein species with an apparent molecular mass of 15 kDa. To characterize further these E6 and E7 proteins, C127 cells were transformed by transfection with BPV-1 genomes containing mutations predicted to prevent expression of specific E6 or E7 gene products, and the transformed cells were subjected to immunoprecipitation analysis with the E6 or E7 antiserum. The results of these experiments confirmed that the E6 and E7 ORFs encode distinct proteins and failed to establish the existence of an E6/7 fusion protein. We did not find a significant difference in the viral genome copy number between clonal C127 cell lines transformed by wild-type BPV-1 or by mutant viral genomes unable to express the E6 or the E7 protein. Furthermore, in contrast to two previous reports suggesting that expression of the BPV-1 E5 gene was required for the establishment or maintenance of a high viral plasmid copy number, we observed a two- to fourfold increase over wild-type BPV-1 plasmid copy number in C127 cells transfected with a BPV-1 E5-minus mutant and subsequently selected by neoplastic focus formation.
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Affiliation(s)
- N Jareborg
- Department of Medical Genetics, Biomedical Center, Uppsala, Sweden
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2
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McBride AA, Howley PM. Bovine papillomavirus with a mutation in the E2 serine 301 phosphorylation site replicates at a high copy number. J Virol 1991; 65:6528-34. [PMID: 1658358 PMCID: PMC250703 DOI: 10.1128/jvi.65.12.6528-6534.1991] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The E2 open reading frame of bovine papillomavirus type 1 (BPV-1) encodes at least three proteins with transcriptional regulatory properties. The full-length E2 open reading frame encodes a transcriptional transactivator, and the 3' region encodes two smaller polypeptides that repress E2-mediated transactivation. The full-length gene product is also required for viral DNA replication. We have demonstrated that the BPV-1 E2 polypeptides are phosphorylated primarily on two serine residues at a site adjacent to the carboxy-terminal DNA binding domain, which is common to all three E2 proteins (A. A. McBride, J. B. Bolen, and P. M. Howley, J. Virol. 63:5076-5085, 1989). These serine residues, at amino acid positions 298 and 301, were substituted with alanine residues in the context of the entire BPV-1 genome. The mutated BPV-1 genomes were introduced into rodent cell lines and assayed for focus formation, viral gene expression, and extrachromosomal viral DNA replication. Viral DNAs containing the E2 serine-to-alanine substitution mutants transformed C127 cells with efficiencies comparable to that of wild-type BPV-1. However, the viral genome containing the serine-to-alanine substitution at position 301 of the E2 polypeptide replicated to a copy number 20-fold higher than that of wild-type DNA.
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Affiliation(s)
- A A McBride
- Laboratory of Tumor Virus Biology, National Cancer Institute, Bethesda, Maryland 20892
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3
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Riese DJ, Settleman J, Neary K, DiMaio D. Bovine papillomavirus E2 repressor mutant displays a high-copy-number phenotype and enhanced transforming activity. J Virol 1990; 64:944-9. [PMID: 2153255 PMCID: PMC249196 DOI: 10.1128/jvi.64.2.944-949.1990] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The methionine codon at bovine papillomavirus type 1 nucleotide 3091 was mutated to determine whether it may serve as an initiation codon for an E2 transcriptional repressor protein and to determine the role of the repressor in the biological activities of the virus. A series of transient expression experiments with CV1 cells documented that the mutation reduced expression of repressor activity from the viral genome and resulted in increased expression of the E5 transforming gene. Viral genomes containing the mutation displayed enhanced transforming activity in several assays in mouse C127 cells, including focus formation, colony formation in agarose, and tumorigenicity. In transformed cells, the mutant viral DNA was maintained as a plasmid with approximately 500 genomes per cell, whereas the wild-type copy number was approximately 75. These results indicate that the wild-type bovine papillomavirus type 1 genome encodes an E2 repressor protein that moderates the viral transforming activity and allows maintenance of the viral DNA at a relatively low copy number.
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Affiliation(s)
- D J Riese
- Department of Human Genetics, Yale University School of Medicine, New Haven, Connecticut 06510
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4
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Selective enhancement of bovine papillomavirus type 1 DNA replication in Xenopus laevis eggs by the E6 gene product. Mol Cell Biol 1989. [PMID: 2540419 DOI: 10.1128/mcb.9.2.406] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Genetic analyses of bovine papillomavirus type 1 (BPV-1) DNA in transformed mammalian cells have indicated that the E6 gene product is essential for the establishment and maintenance of a high plasmid copy number. In order to analyze the direct effect of the E6 protein on the replication of a BPV-1-derived plasmid, a cDNA containing the BPV-1 E6 open reading frame was subcloned into an SP6 vector for the in vitro synthesis of the corresponding mRNA. The SP6 E6 mRNA was injected into Xenopus laevis oocytes to determine the subcellular localization of the E6 gene product and to analyze the effect of the protein on BPV-1 DNA replication. SP6 E6 mRNA microinjected into stage VI oocytes was translated into a 15.5-kilodalton protein that was specifically immunoprecipitated by antibodies directed against the E6 gene product. The E6 protein preferentially accumulated in oocyte nuclei, a localization which is consistent with the replicative functions in which it has been implicated. The expression of E6 in replication-competent mature oocytes selectively enhanced the replication of a BPV-derived plasmid, indicating a direct role for this gene product in the control of BPV-1 DNA replication.
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5
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Romanczuk H, Wormington WM. Selective enhancement of bovine papillomavirus type 1 DNA replication in Xenopus laevis eggs by the E6 gene product. Mol Cell Biol 1989; 9:406-14. [PMID: 2540419 PMCID: PMC362615 DOI: 10.1128/mcb.9.2.406-414.1989] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Genetic analyses of bovine papillomavirus type 1 (BPV-1) DNA in transformed mammalian cells have indicated that the E6 gene product is essential for the establishment and maintenance of a high plasmid copy number. In order to analyze the direct effect of the E6 protein on the replication of a BPV-1-derived plasmid, a cDNA containing the BPV-1 E6 open reading frame was subcloned into an SP6 vector for the in vitro synthesis of the corresponding mRNA. The SP6 E6 mRNA was injected into Xenopus laevis oocytes to determine the subcellular localization of the E6 gene product and to analyze the effect of the protein on BPV-1 DNA replication. SP6 E6 mRNA microinjected into stage VI oocytes was translated into a 15.5-kilodalton protein that was specifically immunoprecipitated by antibodies directed against the E6 gene product. The E6 protein preferentially accumulated in oocyte nuclei, a localization which is consistent with the replicative functions in which it has been implicated. The expression of E6 in replication-competent mature oocytes selectively enhanced the replication of a BPV-derived plasmid, indicating a direct role for this gene product in the control of BPV-1 DNA replication.
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Affiliation(s)
- H Romanczuk
- Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02254
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6
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Choo KB, Cheung WF, Liew LN, Lee HH, Han SH. Presence of catenated human papillomavirus type 16 episomes in a cervical carcinoma cell line. J Virol 1989; 63:782-9. [PMID: 2536104 PMCID: PMC247751 DOI: 10.1128/jvi.63.2.782-789.1989] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Human papillomavirus (HPV) is frequently associated with cervical carcinoma and derived cell lines. In primary tissues of the carcinoma, the viral genome may be present in episomal or integrated configuration. In cell lines, however, only integrated HPV sequences have been reported. In this article, we describe the presence of episomal type 16 HPV (HPV16), demonstrated by electron microscopy and two-dimensional agarose gel electrophoresis, in a cervical carcinoma cell line, CC7T/VGH, established in 1980 in Taiwan. In CC7T/VGH, the HPV16 sequences are transcriptionally active, and at least three major HPV16 RNA species were detected in Northern blots. Results from restriction enzyme and S1 nuclease analysis suggest a composition of oligomeric HPV16 molecules in dimeric repeats. In addition, the HPV16 oligomers exist as catenated molecules of interlocking rings instead of concatemers. A monomeric copy of the HPV16 episome was cloned from a Hirt supernatant of CC7T/VGH by using a plasmid vector. Mapping and partial sequencing studies revealed an internal deletion of 163 base pairs within the L1 open reading frame. However, insertion of an A.C nucleotide pair at the deletion junction restored the otherwise frame-shifted L1 open reading frame. Two base transitions were also found within the E7 and the E1 open reading frames. Our findings suggest the need for closer examination for HPV episomal catenation in other cervical carcinoma cell lines as well as in primary carcinoma tissues of the uterine cervix and the anogenital tract. With CC7T/VGH, a way is now available for studies of many important aspects of the biology of HPV such as replication and gene expression of the extrachromosomal viral genome.
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Affiliation(s)
- K B Choo
- Department of Medical Research, Veterans General Hospital, Taipei, Taiwan, Republic of China
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7
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Neary K, DiMaio D. Open reading frames E6 and E7 of bovine papillomavirus type 1 are both required for full transformation of mouse C127 cells. J Virol 1989; 63:259-66. [PMID: 2535732 PMCID: PMC247680 DOI: 10.1128/jvi.63.1.259-266.1989] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
A series of mutations in open reading frames (ORFs) E6 and E7 of bovine papillomavirus type 1 (BPV1) was constructed to analyze the roles of these ORFs in transformation of mouse C127 cells. The mutations were designed to prevent synthesis of specific proteins encoded by these genes. None of the mutations caused a decrease in the focus-forming activity of the full-length viral genome or in the ability of the viral DNA to replicate as a high-copy-number plasmid. Analysis of these mutants in the absence of a functional BPV1 E5 gene revealed a weak focus-forming activity encoded by ORF E6. Mutations preventing synthesis of the E6 protein did cause defects in anchorage-independent growth and tumorigenicity of transfected and transformed cells. However, a frameshift mutation between the first and second ATG codons of ORF E6 did not inhibit induction of colony formation, suggesting that translation from the first methionine codon is not required. Mutations that inactivated ORF E7 or E6/E7 individually did not inhibit induction of colony formation in agarose. However, a defect in this activity was caused by simultaneous disruption of both ORF E7 and ORF E6/E7 when they were expressed from the full-length viral genome but not when they were expressed under the control of a retrovirus long terminal repeat. These results suggest that translation of both ORF E6 and the 3' end of ORF E7 is required for efficient induction of anchorage-independent growth by the intact BPV1 genome.
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Affiliation(s)
- K Neary
- Department of Human Genetics, Yale University School of Medicine, New Haven, Connecticut 06510-8005
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8
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Petti L, Sample J, Wang F, Kieff E. A fifth Epstein-Barr virus nuclear protein (EBNA3C) is expressed in latently infected growth-transformed lymphocytes. J Virol 1988; 62:1330-8. [PMID: 2831394 PMCID: PMC253145 DOI: 10.1128/jvi.62.4.1330-1338.1988] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Three distantly homologous neighboring long open reading frames in the Epstein-Barr virus (EBV) genome are preceded by short open reading frames. The leftmost short and long open reading frames encode EBNA3, a nuclear protein which is slightly smaller (145 kilodaltons [kDa]) than two other nuclear proteins (150 to 155 kDa) detected in Western blots (immunoblots) of latently infected cell protein (K. Hennessy, F. Wang, E. Woodland-Bushman, and E. Kieff, Proc. Natl. Acad. Sci. USA 83:5693-5697, 1986; I. Joab, D. T. Rowe, M. Bodescot, J.-C. Nicolas, P. J. Farrell, and M. Perricaudet, J. Virol. 61:3340-3344, 1987). We have demonstrated that the most rightward short (BERF3) and long (BERF4) open reading frames are spliced in frame at the 3' end of a 5-kilobase latently infected cell RNA and that this RNA begins within or upstream of the EBV long internal repeat. EBV-immune human antibodies specific for the long open reading frame translation product identified a 155-kDa protein on Western blots of latently infected cell protein and specifically reacted with large nonnucleolar nuclear granules in every latently infected cell. Expression of the cDNA in BALB/c 3T3 cells resulted in translation of full-size EBNA3C but had no effect on cell morphology, contact inhibition, or serum independence.
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Affiliation(s)
- L Petti
- Kovler Viral Oncology Laboratory, University of Chicago, Illinois 60637
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9
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Gius D, Grossman S, Bedell MA, Laimins LA. Inducible and constitutive enhancer domains in the noncoding region of human papillomavirus type 18. J Virol 1988; 62:665-72. [PMID: 2828662 PMCID: PMC253618 DOI: 10.1128/jvi.62.3.665-672.1988] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The noncoding region of human papillomavirus type 18 (HPV-18) is shown to contain at least three enhancer elements. Two of these elements are responsive to papillomavirus-encoded trans-acting factors, and the third element functions as a constitutive enhancer, requiring only cellular factors for activity. The first enhancer (IE2) is located proximal to the E6 cap site and is responsive to papillomavirus E2 trans-activator. The second enhancer (IE6) is located approximately 500 base pairs upstream of the E6 cap site and is dependent upon the viral E6 gene product for function. A third enhancer (C) is located between 200 and 400 base pairs upstream of the E6 cap site and possesses a constitutive activity, requiring no HPV-18-encoded factors for function. The constitutive enhancer element exhibits some cell type preference for epithelial cell lines, but also functions in rodent fibroblast lines. Each of these enhancers manifests activity independent of the other elements and may reflect separate transcriptional control elements for different stages of the HPV-18 virus life cycle.
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Affiliation(s)
- D Gius
- Committee on Virology, University of Chicago, Illinois 60637
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10
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Harrison SM, Gearing KL, Kim SY, Kingsman AJ, Kingsman SM. Multiple cis-active elements in the long control region of bovine papillomavirus type 1 (BPV-1). Nucleic Acids Res 1987; 15:10267-84. [PMID: 2827118 PMCID: PMC339943 DOI: 10.1093/nar/15.24.10267] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
A 1.0 kb region of the BPV-1 genome (the long control region, LCR), contains controls for transcription and the origin of replication. Transcription directed by the LCR is activated by the viral encoded E2 protein. To define the essential cis acting elements that are required to control transcription we have constructed a series of deletions throughout the LCR. We have identified three important domains in the LCR, two of which respond to E2. We have analysed the ability of small subcloned regions of the E2 responsive domains to act as enhancers in a heterologous assay system. This has led to the identification of five independent E2 responsive elements. We have shown that a fragment of only 38 base pairs is sufficient to respond to activation by E2. We also present evidence to suggest two types of E2 responsiveness that result in strong or weak activation. Strong response is correlated with the presence of the sequence 5'-ACCG/TNNNC/TCGGTGC-3' whereas weak response is correlated with the presence of a related sequence 5'-ACC(N)6GGT-3'. The contribution of these multiple elements to viral transcription is discussed.
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Affiliation(s)
- S M Harrison
- Department of Biochemistry, University of Oxford, UK
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11
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Stephens PE, Hentschel CC. The bovine papillomavirus genome and its uses as a eukaryotic vector. Biochem J 1987; 248:1-11. [PMID: 2829815 PMCID: PMC1148493 DOI: 10.1042/bj2480001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- P E Stephens
- Department of Molecular Genetics, Celltech Ltd., Berkshire, U.K
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12
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Burnett S, Moreno-Lopez J, Pettersson U. Messenger RNAs from the E1 region of bovine papillomavirus type 1 detected in virus-infected bovine cells. Nucleic Acids Res 1987; 15:8607-20. [PMID: 2825116 PMCID: PMC306394 DOI: 10.1093/nar/15.21.8607] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Bovine papillomavirus type 1 DNA replicated to a high copy number in virus-infected bovine fibroblasts. Infected bovine cells were therefore used as a source of RNA for Northern blotting analysis to search for viral transcripts hybridizing to the E1 gene region, implicated in viral DNA replication. Cytoplasmic polyadenylated RNA preparations contained at least five different E1-region transcripts, ranging from 1200 to approximately 4500 nucleotides in length. All of these species contained sequence information from the 5'-end of the E1 open reading frame, but only the largest species included sequences from its central portion. The latter transcript is a candidate mRNA for a stimulatory replication factor (R) previously mapped by genetic experiments (1).
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Affiliation(s)
- S Burnett
- Department of Medical Genetics, University of Uppsala, Sweden
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13
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Chow LT, Reilly SS, Broker TR, Taichman LB. Identification and mapping of human papillomavirus type 1 RNA transcripts recovered from plantar warts and infected epithelial cell cultures. J Virol 1987; 61:1913-8. [PMID: 2883327 PMCID: PMC254198 DOI: 10.1128/jvi.61.6.1913-1918.1987] [Citation(s) in RCA: 68] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Multiple spliced transcripts of human papillomavirus type 1 were detected by electron microscopic analysis of R-loops formed with total RNA extracted from plantar warts and with poly(A)+ RNA isolated from cultured keratinocytes infected with human papillomavirus type 1. The 5' ends of the RNAs were mapped to sites in the E7 open reading frame (ORF), just upstream of the E6 ORF and in the upstream regulatory region. Species with 5' ends in E7 accounted for over 95% of all transcripts seen. Two polyadenylation sites were used, one at the end of the early (E) region of the viral DNA, the other at the end of the late (L) region. The most abundant species had a short 5' exon of approximately 100 nucleotides spanning the junction of the E7 and E1 ORFs spliced to a 3' exon of 800 nucleotides in the region with overlapping E2 and E4 ORFs; it was polyadenylated at the end of the E region. This species probably encodes the abundant E4 protein found in plantar warts (F. Breitburd, O. Croissant, and G. Orth, Cancer Cells, vol. 5, in press; J. Doorbar, D. Campbell, R. J. A. Grand, and P. H. Gallimore, EMBO J. 5:355-362, 1986). Other transcripts had exons spanning the E6-E7 ORFs, the E4-E5-L2-L1 ORFs, or the L1 ORF. The infrequent L1 transcript, probably the mRNA coding for the major capsid protein, had the same 5' exon in E7 as the abundant mRNA spliced from E1 and E4 ORFs, suggesting genetic regulation via the choice of the alternative polyadenylation sites or mRNA processing.
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14
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Smotkin D, Wettstein FO. The major human papillomavirus protein in cervical cancers is a cytoplasmic phosphoprotein. J Virol 1987; 61:1686-9. [PMID: 3033296 PMCID: PMC254156 DOI: 10.1128/jvi.61.5.1686-1689.1987] [Citation(s) in RCA: 150] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
In a previous study, the most abundant viral transcript in a human papillomavirus type 16-associated cervical cancer and in a cancer-derived cell line was characterized, and its translation product, the E7 protein, was identified (D. Smotkin and F. O. Wettstein, Proc. Natl. Acad. Sci. USA 68:4680-4684, 1986). Here we show that the E7 protein had a half life of about 1 h and was located in the soluble cytoplasmic fraction. The protein was phosphorylated at serine residues and exhibited a high heterogeneous sedimentation rate in nondenaturing glycerol gradients, suggesting an oligomer formation or association with cellular protein.
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15
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Baker CC, Howley PM. Differential promoter utilization by the bovine papillomavirus in transformed cells and productively infected wart tissues. EMBO J 1987; 6:1027-35. [PMID: 3036488 PMCID: PMC553499 DOI: 10.1002/j.1460-2075.1987.tb04855.x] [Citation(s) in RCA: 98] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Expression of the 'late' genes of bovine papillomavirus type 1 (BPV-1) occurs only in the differentiated keratinocytes of the productively infected fibropapilloma. A detailed analysis of viral transcription in the fibropapilloma was performed and compared to BPV-1 specific transcription in transformed C127 cells. A cDNA library was constructed from bovine fibropapilloma mRNA using the method of Okayama and Berg. Analysis of full length cDNAs showed that the majority of viral transcripts in the fibropapilloma have 5' termini near nt 7250 and utilize a common splice donor site at nt 7385. This mRNA start site was confirmed by the combination of primer extension and nuclease S1 analyses; it is not utilized in the BPV-1-transformed C127 cell, thus identifying it as a wart specific, 'late' promoter. Upstream of this mRNA start site is a tandemly repeated sequence element homologous to the SV40 late promoter sequence GGTACCTAACC, which has been shown to be important for the efficient utilization of the SV40 major late start site. Two additional mRNA start sites at nt 7185 and nt 7940 in the long control region (LCR) were identified and were found to be used in bovine warts as well as in BPV-1-transformed mouse cells. The promoter region upstream of the nt 7940 mRNA start site contains the E2 responsive enhancer mapping between nt 7611 and nt 7805 [Spalholz, B.A., Lambert, P.F., Yee, C. and Howley, P.M. (1987) J. Virol., in press].(ABSTRACT TRUNCATED AT 250 WORDS)
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16
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Neary K, Horwitz BH, DiMaio D. Mutational analysis of open reading frame E4 of bovine papillomavirus type 1. J Virol 1987; 61:1248-52. [PMID: 3029420 PMCID: PMC254088 DOI: 10.1128/jvi.61.4.1248-1252.1987] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Open reading frame (ORF) E4 is a 353-base-pair ORF of bovine papillomavirus type 1. To determine the biological activities of this ORF in mouse C127 cells, we analyzed the effects of two constructed mutations which are predicted to prevent synthesis of ORF E4 proteins while leaving the amino acid sequence encoded by the overlapping ORF E2 unchanged. Neither mutation interfered with the abilities of the mutants to efficiently induce focus formation, induce growth in soft agarose, or transactivate an inducible bovine papillomavirus type 1 enhancer. Also, neither mutation prevented establishment of the viral DNA as an extrachromosomal plasmid in transformed cells. These results suggest that ORF E4 proteins are not required for these biological activities, and they are consistent with the observation of others (J. Doorbar, D. Campbell, R. J. A. Grand, and P. H. Gallimore, EMBO J. 5:355-362, 1986) that the ORF E4 protein of a human papillomavirus is associated with late gene expression during papilloma formation.
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17
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Moskaluk C, Bastia D. The E2 "gene" of bovine papillomavirus encodes an enhancer-binding protein. Proc Natl Acad Sci U S A 1987; 84:1215-8. [PMID: 3029771 PMCID: PMC304397 DOI: 10.1073/pnas.84.5.1215] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The E2 early open reading frame (presumably gene) of bovine papillomavirus-1 was fused in frame with the collagen-beta-galactosidase-encoding region of the vector pJG200 and was expressed in and partially purified from Escherichia coli. The hybrid protein specifically bound to the enhancer region of bovine papillomavirus at several sites. DNase I-cleavage protection analysis of one such site revealed the protected sequence. A comparison of the protected sequence with the remainder of the DNA sequences that also have affinity for the protein revealed a consensus sequence having the motif AATTGGCGGNNCG, in which N is any nucleotide. The protected region also includes a sequence with 2-fold rotational symmetry--ATCGGTG/CACCGAT.
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18
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Haugen TH, Cripe TP, Ginder GD, Karin M, Turek LP. Trans-activation of an upstream early gene promoter of bovine papilloma virus-1 by a product of the viral E2 gene. EMBO J 1987; 6:145-52. [PMID: 3034572 PMCID: PMC553370 DOI: 10.1002/j.1460-2075.1987.tb04732.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The approximately 1000 nucleotide long upstream regulatory region (URR) of bovine papilloma virus-1 (BPV-1) contains a cis element which responds to trans-activation by a diffusible factor encoded in the viral E2 open reading frame (ORF). A series of URR DNA fragments have been linked to two heterologous genes, bacterial chloramphenicol acetyl transferase (cat) or herpes simplex virus-1 thymidine kinase (tk), and tested in transient transfection assays for transcription initiating at the authentic upstream early viral promoter, P89. Transcriptional activity of the P89 promoter was greatly elevated in the presence of the E2 trans-activator gene product. The E2-responsive cis element (E2R) of P89 has been mapped to sequences -277 to -131 nucleotides upstream from the transcription start site (BPV nucleotide 89). The E2R element functioned as a strong transcriptional enhancer in cis with the SV40 early or the tk promoter in the presence, but not in the absence, of the E2 gene product. However, several heterologous promoters which lack sequences related to the E2R element were also trans-activated in transient cotransfections by a function encoded in the E2 ORF of BPV-1, albeit to a much lesser extent. In addition to activation of early viral gene transcription, the E2 regulatory gene(s) may therefore have the potential to alter cellular gene expression.
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Lusky M, Botchan MR. A bovine papillomavirus type 1-encoded modulator function is dispensable for transient viral replication but is required for establishment of the stable plasmid state. J Virol 1986; 60:729-42. [PMID: 3022005 PMCID: PMC288948 DOI: 10.1128/jvi.60.2.729-742.1986] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
A bovine papillomavirus (BPV) type 1-encoded function (M) which is a negative regulator of viral plasmid replication has been described elsewhere (Berg et al. Cell, in press; Roberts and Weintraub, Cell, in press). We report here that expression of M, which is a repressor of transient BPV replication and is not required as a positive factor in these assays, is required for the establishment of the viral genome as a stable nuclear plasmid. This function is encoded in part by the 5' portion of the BPV E1 open reading frame, whereas the 3' part of this open reading frame encodes a positive replication function (R). The R function is required for early replication events. We used transient replication assays to define the phenotypes of mutants in both the R and M genes and complementation tests to show that R and M define two separate genes. We showed that R- and M- mutants could also complement each other in stable assays. In cotransfection experiments, M- mutants had a lethal effect on the growth of G418-resistant colonies, and in addition their morphological transformation efficiencies were reduced. The rare colonies which did appear contained the mutant DNA integrated into the cellular genome. R- mutants transformed with wild-type efficiency, and the mutant DNA was also found integrated. When cotransfected, R- and M- mutants could each be established as unrearranged plasmids.
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Lusky M, Botchan MR. Transient replication of bovine papilloma virus type 1 plasmids: cis and trans requirements. Proc Natl Acad Sci U S A 1986; 83:3609-13. [PMID: 3012521 PMCID: PMC323572 DOI: 10.1073/pnas.83.11.3609] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
A transient assay has been used to study bovine papilloma virus type 1 (BPV-1) replication. We show that BPV-1 early replication occurs faster than cellular DNA synthesis. Initial replication events are dependent on a gene product(s), encoded by the BPV-1 E1 open reading frame. Mutational analysis of the viral upstream regulatory region shows the requirement of two domains in cis for replication. Domain one, located outside of the viral 69% transforming fragment, is an enhancer-like activity and can be replaced by other known viral enhancers. Domain two lies within sequences previously defined as plasmid maintenance sequence 1. The apparent requirement for a proximal enhancer function for replication may explain why certain BPV-1 constructions, when linked to bacterial plasmid sequences, can be maintained extrachromosomally while others cannot.
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