DNA Packaging by L1 and L2 Capsid Proteins of Bovine Papillomavirus Type 1

Zhao, Kong‐Nan; Sun, Xiaoyi; Frazer, Ian H.; Zhou, Jiang

doi:10.1006/viro.1998.9091

Cited by 63 publications

(51 citation statements)

References 41 publications

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“…L2 has been shown to be necessary for DNA packaging in some PV types (16,57,58) and is likely to have additional roles during infection. As envisioned in the proposed model, L2 has the novel postentry role of delivering the genome to ND10, where it can be efficiently transcribed, in contrast to other nuclear DNA viruses, which initially localize to ND10 and then induce ND10 dissolution.…”

Section: Discussionmentioning

confidence: 99%

Establishment of papillomavirus infection is enhanced by promyelocytic leukemia protein (PML) expression

Day

Baker

Lowy

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

216

277

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Previous studies have suggested that most papillomaviruses enter the host cell via clathrin-dependent receptor-mediated endocytosis but have not addressed later steps in viral entry. To examine these events, we followed the localization of L2 and packaged DNA after entry of infectious virions or L1͞L2 pseudovirions. Confocal microscopic analyses of HeLa cells showed a time-dependent uncoating of capsids in cytoplasmic vesicles and the accumulation of both L2 and viral DNA at distinct nuclear domains identified as nuclear domain 10 (ND10). Both L2 and the pseudogenome had a punctate distribution and localized to ND10 in promyelocytic leukemia protein (PML)-expressing cells, whereas L2 had a diffuse nuclear distribution in PML؊͞؊ cells. The number of pseudovirus-infected cells was an order of magnitude higher in the PML؉ cells compared with the PML؊͞؊ cells, and viral genome transcription after infection with authentic bovine papillomavirus virions was similarly elevated in PML؉ cells. The results identify a role for PML in the enhancement of viral infectivity in the early part of the life cycle. We propose a model in which L2 chaperones the viral genome to ND10 to efficiently initiate viral transcription.

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Section: Discussionmentioning

confidence: 99%

Establishment of papillomavirus infection is enhanced by promyelocytic leukemia protein (PML) expression

Day

Baker

Lowy

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

216

277

View full text Add to dashboard Cite

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“…Rather, they made use of heterologous systems in which L1 and L2 were overexpressed in irrelevant cell types from heterologous promoters in the context of viral or plasmid-based expression vectors, and the viral genome or some heterologous plasmid to be packaged was provided in trans via transfection, sometimes under conditions in which the DNA being packaged was highly amplified using a simian virus 40 replication origin. These nonphysiological conditions likely contribute to the fact that in some cases L2 is observed to influence the degree of DNA encapsidation (4,20,25,26,32,33) and in others it is not (28,29).…”

Section: Discussionmentioning

confidence: 99%

“…Different investigators have obtained conflicting results. Some found that in their system L2 was required for the encapsidation of viral or reporter DNA (4,20,25,26,32,33). In other systems L2 was not required (28,29).…”

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confidence: 99%

The Minor Capsid Protein L2 Contributes to Two Steps in the Human Papillomavirus Type 31 Life Cycle

Holmgren

Patterson

Ozbun

et al. 2005

J Virol

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Prior studies, which have relied upon the use of pseudovirions generated in heterologous cell types, have led to sometimes conflicting conclusions regarding the role of the minor capsid protein of papillomaviruses, L2, in the viral life cycle. In this study we carry out analyses with true virus particles assembled in the natural host cell to assess L2's role in the viral infectious life cycle. For these studies we used the organotypic (raft) culture system to recapitulate the full viral life cycle of the high-risk human papillomavirus HPV31, which was either wild type or mutant for L2. After transfection, the L2 mutant HPV31 genome was able to establish itself as a nuclear plasmid in proliferating populations of poorly differentiated (basal-like) human keratinocytes and to amplify its genome to high copy number, support late viral gene expression, and cause formation of virus particles in human keratinocytes that had been induced to undergo terminal differentiation. These results indicate that aspects of both the nonproductive and productive phases of the viral life cycle occur normally in the absence of functional L2. However, upon the analysis of the virus particles generated, we found an approximate 10-fold reduction in the amount of viral DNA encapsidated into L2-deficient virions. Furthermore, there was an over-100-fold reduction in the infectivity of L2-deficient virus. Because the latter deficiency cannot be accounted for solely by the 10-fold decrease in encapsidation, we conclude that L2 contributes to at least two steps in the production of infectious virus.Papillomaviruses are small icosahedral viruses with doublestranded, circular DNA genomes that infect the stratified squamous epithelial tissues of vertebrates. The infection commonly results in a papilloma, or wart, formation. A small subset of the human-specific genotypes termed the high-risk human papillomaviruses (HPVs), including HPV31, have the capacity to cause cancer, most notably cervical cancer (35). Understanding the papillomaviral life cycle may allow us to establish the means to inhibit high-risk papillomaviral infections and thereby prevent HPV-associated cancers. In this study, we investigated the role the minor capsid protein, L2, plays in the papillomaviral life cycle.The life cycle of papillomaviruses is intricately tied to the differentiation of their host tissue, stratified squamous epithelium (23). In the poorly differentiated basal cells, which comprise the proliferating compartment of the epithelium and where papillomaviral infection is thought to arise, the viral genome takes up residence as a stable, nuclear plasmid that is maintained at low copy number. Only a subset of viral genes, the early genes, is selectively expressed in the basal compartment, and therefore no new virus is made there. Consequently, we refer to the infective state in the basal compartment as the nonproductive phase of the life cycle. As basal cells proliferate and undergo cell division, daughter cells that lose contact with the underlying basement membr...

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“…A consequence of the extensive regulation of the late phase of the papillomavirus life cycle is that recapitulating the assembly of papillomaviruses in cultured cells has posed a substantial challenge. A variety of systems have been developed for in vitro production of infectious papillomaviruses and papillomavirus-based gene transfer vectors (which are also known as papillomavirus pseudoviruses) (5,6,16,25,28,35,41,47,49). However, currently available systems are technically demanding and relatively low-yield.…”

mentioning

confidence: 99%

Efficient Intracellular Assembly of Papillomaviral Vectors

Buck

Pastrana

Lowy

et al. 2004

J Virol

439

521

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Although the papillomavirus structural proteins, L1 and L2, can spontaneously coassemble to form viruslike particles, currently available methods for production of L1/L2 particles capable of transducing reporter plasmids into mammalian cells are technically demanding and relatively low-yield. In this report, we describe a simple 293 cell transfection method for efficient intracellular production of papillomaviral-based gene transfer vectors carrying reporter plasmids. Using bovine papillomavirus type 1 (BPV1) and human papillomavirus type 16 as model papillomaviruses, we have developed a system for producing papillomaviral vector stocks with titers of several billion transducing units per milliliter. Production of these vectors requires both L1 and L2, and transduction can be prevented by papillomavirus-neutralizing antibodies. The stocks can be purified by an iodixanol (OptiPrep) gradient centrifugation procedure that is substantially more effective than standard cesium chloride gradient purification. Although earlier data had suggested a potential role for the viral early protein E2, we found that E2 protein expression did not enhance the intracellular production of BPV1 vectors. It was also possible to encapsidate reporter plasmids devoid of BPV1 DNA sequences. BPV1 vector production efficiency was significantly influenced by the size of the target plasmid being packaged. Use of 6-kb target plasmids resulted in BPV1 vector yields that were higher than those with target plasmids closer to the native 7.9-kb size of papillomavirus genomes. The results suggest that the intracellular assembly of papillomavirus structural proteins around heterologous reporter plasmids is surprisingly promiscuous and may be driven primarily by a size discrimination mechanism.Papillomaviruses are small nonenveloped viruses with double-stranded circular DNA genomes. They replicate in stratified squamous epithelial tissues, such as the skin or mucosa. The outermost layers of these tissues are thought to be relatively secluded from immunological surveillance. Papillomaviruses exploit this weakness by restricting virion production to the outer, terminally differentiated layers of the epithelium (36). A consequence of the extensive regulation of the late phase of the papillomavirus life cycle is that recapitulating the assembly of papillomaviruses in cultured cells has posed a substantial challenge. A variety of systems have been developed for in vitro production of infectious papillomaviruses and papillomavirus-based gene transfer vectors (which are also known as papillomavirus pseudoviruses) (5,6,16,25,28,35,41,47,49). However, currently available systems are technically demanding and relatively low-yield.Many details of the assembly of papillomaviruses remain unclear. Previous work using recombinant Semliki Forest virus (SFV) and vaccinia virus expression systems has shown that the papillomavirus minor virion protein, L2, can induce relocalization of the major virion protein, L1, to subnuclear domains known as promyelocytic oncogenic d...

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DNA Packaging by L1 and L2 Capsid Proteins of Bovine Papillomavirus Type 1

Cited by 63 publications

References 41 publications

Establishment of papillomavirus infection is enhanced by promyelocytic leukemia protein (PML) expression

Establishment of papillomavirus infection is enhanced by promyelocytic leukemia protein (PML) expression

The Minor Capsid Protein L2 Contributes to Two Steps in the Human Papillomavirus Type 31 Life Cycle

Efficient Intracellular Assembly of Papillomaviral Vectors

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