Cis and trans requirements for stable episomal maintenance of the BPV-1 replicator.

Piirsoo, Marko; Ustav, Ene; Mandel, Tiiu; Stenlund, Arne; Ustav, Mart

doi:10.1002/j.1460-2075.1996.tb00328.x

Cited by 138 publications

(171 citation statements)

References 47 publications

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“…Multiple E2 binding sites are required in addition for the genome to be stably maintained in dividing cells (2). The bovine papillomavirus (BPV) type 1 E2 protein tethers the genomes by means of the E2 binding sites to cellular mitotic chromosomes (3)(4)(5) to ensure that they are retained in the nucleus and distributed to daughter cells.…”

mentioning

confidence: 99%

Variations in the association of papillomavirus E2 proteins with mitotic chromosomes

Oliveira

Colf

McBride

2006

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

101

145

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The E2 protein segregates episomal bovine papillomavirus (BPV) genomes to daughter cells by tethering them to mitotic chromosomes, thus ensuring equal distribution and retention of viral DNA. To date, only the BPV1 E2 protein has been shown to bind to mitotic chromosomes. We assessed the localization of 13 different animal and human E2 proteins from seven papillomavirus genera, and we show that most of them are stably bound to chromosomes throughout mitosis. Furthermore, in contrast to the random association of BPV1 E2 with mitotic chromosomes, several of these proteins appear to bind to more specific regions of mitotic chromosomes. Using human papillomavirus (HPV) type 8 E2, we show that this region is adjacent to centromeres͞kinetochores. Therefore, E2 proteins from both HPV and animal papillomavirus bind to mitotic chromosomes, and there are variations in the specificity of this binding. Only the ␣-papillomavirus E2 proteins do not stably associate with mitotic chromatin throughout mitosis. These proteins closely associate with prophase chromosomes and bind to chromosomes in telophase but not in metaphase. However, extraction of mitotic cells before fixation results in ␣-E2 proteins binding to the pericentromeric region of metaphase chromosomes, as observed for HPV8 E2. We postulate that this is the authentic target of these E2 proteins but that additional factors or a specialized cellular environment is required to stabilize this association. Thus, E2-mediated tethering of viral genomes to mitotic chromosomes is a common strategy of papillomaviruses, but different viruses have evolved different variations of this theme.human papillomavirus ͉ mitosis ͉ replication ͉ segregation T here are 17 distinct genera of Papillomaviridae (1); each virus infects a specific region of cutaneous or mucosal epithelium in a particular host. For example, human papillomavirus (HPV) types 1, 2, 3, and 4 cause plantar and palmar warts whereas HPV5 and HPV8 are found in cutaneous lesions of epidermodysplasia verruciformis. Mucosal HPV types such as HPV6, HPV11, HPV16, and HPV31 infect genital and sometimes oral epithelia. These infections are usually persistent, and so papillomaviruses need a mechanism to efficiently retain the extrachromosomal genomes within dividing cells.The viral E1 and E2 proteins initiate viral DNA replication by binding to the replication origin. Multiple E2 binding sites are required in addition for the genome to be stably maintained in dividing cells (2). The bovine papillomavirus (BPV) type 1 E2 protein tethers the genomes by means of the E2 binding sites to cellular mitotic chromosomes (3-5) to ensure that they are retained in the nucleus and distributed to daughter cells. This mechanism is a common one in persistent episomal viruses; Epstein-Barr virus and human herpesvirus 8 also each encode a protein that tethers the viral genomes to mitotic chromosomes to ensure their faithful segregation.The E2 protein is also a transcriptional regulator, consisting of a transactivation domain and a dimerization͞DN...

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mentioning

confidence: 99%

Variations in the association of papillomavirus E2 proteins with mitotic chromosomes

Oliveira

Colf

McBride

2006

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

101

145

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“…E2 is a sequence-specific DNA-binding protein that has a number of functions in the viral lifecycle. In addition to its role in the initiation of viral DNA replication, E2 is involved in regulating the transcription of viral genes (2)(3)(4)(5)(6)(7), and in the segregation of the viral genome during cell division (8,9). As a replication initiation factor, E2 binds with high affinity to specific sites located within the viral origin (ori) to help recruit it to the E1 helicase (10 -13).…”

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confidence: 99%

Crystal Structure of the E2 Transactivation Domain of Human Papillomavirus Type 11 Bound to a Protein Interaction Inhibitor

Wang

Coulombe²,

Cameron

et al. 2004

Journal of Biological Chemistry

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Interaction between the E2 protein and E1 helicase of human papillomaviruses (HPVs) is essential for the initiation of viral DNA replication. We recently described a series of small molecules that bind to the N-terminal transactivation domain (TAD) of HPV type 11 E2 and inhibits its interaction with E1 in vitro and in cellular assays. Here we report the crystal structures of both the HPV11 TAD and of a complex between this domain and an inhibitor, at 2.5-and 2.4-Å resolution, respectively. The HPV11 TAD structure is very similar to that of the analogous domain of HPV16. Inhibitor binding caused no significant alteration of the protein backbone, but movements of several amino acid side chains at the binding site, in particular those of Tyr-19, His-32, Leu-94, and Glu-100, resulted in the formation of a deep hydrophobic pocket that accommodates the indandione moiety of the inhibitor. Mutational analysis provides functional evidence for specific interactions between Tyr-19 and E1 and between His-32 and the inhibitor. A second inhibitor molecule is also present at the binding pocket. Although evidence is presented that this second molecule makes only weak interactions with the protein and is likely an artifact of crystallization, its presence defines additional regions of the binding pocket that could be exploited to design more potent inhibitors.Human papillomaviruses (HPVs) 1 are the etiological agents of malignant and benign lesions of the differentiating squamous or mucosal epithelium, notably of cervical cancer. Approximately 25 HPV types replicate in mucosal tissues of the anogenital tract. HPV16, -18, and -31 are the most prevalent "high-risk" types found in pre-cancerous or malignant lesions of the cervix. HPV6 and -11 are the most common "low-risk" types, which cause benign genital warts (condyloma acuminata), a less serious condition but one of the most common sexually transmitted diseases (1). Currently, no specific antivirals are available for the treatment of HPV infections.The small circular double-stranded DNA genome of papillomavirus is actively maintained as a multicopy episome in the nucleus of infected epithelial cells. This process is dependent on replication of the viral genome by the viral E1 and E2 proteins, in conjunction with the host DNA replication machinery. E2 is a sequence-specific DNA-binding protein that has a number of functions in the viral lifecycle. In addition to its role in the initiation of viral DNA replication, E2 is involved in regulating the transcription of viral genes (2-7), and in the segregation of the viral genome during cell division (8, 9). As a replication initiation factor, E2 binds with high affinity to specific sites located within the viral origin (ori) to help recruit it to the E1 helicase (10 -13). Formation of a ternary complex between E1, E2, and the origin relies not only on the interaction of E1 and E2 with specific DNA sequences at the origin but is also critically dependent on a direct interaction between these two proteins (14 -18).The 40-kDa E2 prote...

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“…The major difference between the large T and EBNA1 replication is that the latter initiates replication only once per cell cycle as the replication is under the control of the host origin recognition complex (ORC) (17), while large T initiates replication more than once per cell cycle (18). It is known that HPV E1/E2-mediated replication initiation can also occur more than once per cell cycle (19), however the fidelity of E1/E2-mediated replication is unknown. In many HPV lesions there are episomal genomes that either contain multiple insertions/deletions (20) or single deletions (21,22,23,24).…”

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confidence: 99%

The Fidelity of HPV16 E1/E2-mediated DNA Replication

Taylor

Dornan

Boner

et al. 2003

Journal of Biological Chemistry

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Human papillomaviruses (HPV) are causative agents in a variety of human diseases; for example over 99% of cervical carcinomas contain HPV DNA sequences. Often in cervical carcinoma the HPV genome is integrated into the host genome resulting in unregulated expression of the viral transforming proteins E6 and E7. Therefore viral integration is a step toward HPV-induced carcinogenesis. Integration of the HPV genome could occur following double-strand DNA breaks that could arise during viral DNA replication. We investigated the fidelity of HPV 16 E1-and E2-mediated DNA replication of non-damaged and UVC-damaged templates in a variety of cell lines with different genetic backgrounds; C33a (derived from an HPV-negative cervical carcinoma), XP30RO (deficient in the by-pass polymerase (pol )), XP30 (expressing a restored wild-type pol ), XP12RO (nucleotide excision repair defective), and MRC5 (derived from a 14-week-old human fetus). The results demonstrate that the fidelity of E1-and E2-mediated DNA replication is reflective of the genetic background in which the assays are carried out. Human papilloma viruses (HPVs) 1 are small doublestranded DNA tumor viruses that are causative agents in a variety of human diseases. Over 99% of cervical carcinomas contain HPV sequences; these are of the high-risk type with HPV16 being the most common. The low risk HPVs are causative agents of genital warts, and HPV6/11 are the most commonly found in this disease (1). HPVs are maintained as episomal circular DNA molecules in infected cells and are replicated by the viral proteins E1 and E2 (2, 3). The E2 protein forms homodimers and recognizes and binds to 12bp palindromic DNA sequences in the transcriptional control region of HPV (4). E2 can then regulate transcription from the adjacent promoter that controls the expression of the HPV oncogenes E6 and E7; E2 can either activate or repress transcription depending upon E2 protein levels and the cell type (5, 6). As well as regulating transcription E2 is also essential for replication of the viral genome; there are three E2 DNA binding sequences surrounding the viral origin (ori) of replication and a physical interaction between E2 and E1 results in recruitment of E1 to the ori sequence (7,8,9). Following recruitment by E2 the E1 protein interacts with the ori DNA sequence and then forms a hexameric complex required for replication of the viral genome by virtue of its helicase activity (10). E1 is known to interact with subunits of DNA polymerase-␣ and with components of the Swi/Snf complex in order to activate DNA replication (11,12).In many HPV-induced cervical cancers the HPV genome is found integrated into the host genome. This integration usually deletes the coding sequence for the E2 protein and results in elevated expression of the viral oncoproteins E6 and E7 (13). It is proposed that increased E6 and E7 levels are involved in progression toward carcinoma. Therefore the loss of episomal status of the HPV genome is an important step on the way to carcinogenesis. The integration i...

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Cis and trans requirements for stable episomal maintenance of the BPV-1 replicator.

Cited by 138 publications

References 47 publications

Variations in the association of papillomavirus E2 proteins with mitotic chromosomes

Variations in the association of papillomavirus E2 proteins with mitotic chromosomes

Crystal Structure of the E2 Transactivation Domain of Human Papillomavirus Type 11 Bound to a Protein Interaction Inhibitor

The Fidelity of HPV16 E1/E2-mediated DNA Replication

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