The Mitotic Chromosome Binding Activity of the Papillomavirus E2 Protein Correlates with Interaction with the Cellular Chromosomal Protein, Brd4

Baxter, Michael K.; McPhillips, Maria G.; Ozato, Keiko; McBride, Alison A.

doi:10.1128/jvi.79.8.4806-4818.2005

Cited by 110 publications

(162 citation statements)

References 63 publications

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“…However, several observations argue against an involvement of Brd4 in the E8 Ù E2C mediated repression: First, the Brd4 interaction domain in E2 proteins is completely missing from E8 Ù E2C. 27,32,56,58 Second, in contrast to E2, E8 Ù E2C represses transcription not only from promoter-proximal binding sites but also from promoter-distal binding sites. 39 Third, the E8 Ù E2C protein acts as a repressor of transcription and replication 18,39,40 whereas Brd4 has been reported to contribute also to the activation of transcription and replication by E2.…”

Section: E2c-ha Psg E8mentioning

confidence: 99%

The E8 repression domain can replace the E2 transactivation domain for growth inhibition of HeLa cells by papillomavirus E2 proteins

Stubenrauch

Straub

Fertey

et al. 2007

Intl Journal of Cancer

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Continuous expression of the human papillomavirus (HPV) oncoproteins E6 and E7 is required for the growth of cervical cancer cell lines. So far, only the overexpression of the wild type papillomavirus E2 protein has been shown to induce growth arrest in HPV18-positive HeLa cells by repressing E6/E7 transcription. Growth arrest by E2 requires the aminoterminal transcription activation domain in addition to the carboxyterminal DNA-binding domain. Several papillomaviruses such as the carcinogenic HPV31 express in addition to E2 an E8 Ù E2C fusion protein in which the E8 domain, which is required for repression of replication and transcription, replaces the E2 activation domain. Infections with certain human papillomaviruses (HPV), most notably types 16 and 18, are a necessary risk factor for the development of cervical cancer.1 While the HPV genome is present in an episomal state in low-grade lesions, the whole viral genome or fragments thereof are often integrated into the chromosomal DNA of the host cell in the majority of HPV-induced carcinomas.2 The HeLa cell line was derived from a cervical cancer and contains a partial HPV18 genome integrated into the host chromosomes. 4-7 The E6 and E7 proteins derived from carcinogenic HPVs interfere with cell cycle control proteins. E6 forms a ternary complex with the E3 ubiquitin ligase E6AP and p53, which results in the degradation of p53 and therefore in the reduction of mRNA levels of p53 target genes. 8,9 The E7 protein binds to Rb family members and disrupts Rb/E2F complexes, resulting in increased expression of E2F-regulated genes. 10,11 In addition, the E7 protein enhances degradation of Rb family members. 12,13 A peculiar feature of carcinogenic HPV types is that the E6 and E7 transcripts are generated by alternative splicing from a common precursor RNA.14 Transfection studies using reporter plasmids of the corresponding promoters of HPV16, 18 or 31 demonstrated that coexpression of viral E2 proteins resulted in repression of promoter activity, which is due to binding of E2 to proximal recognition sequences. [15][16][17][18][19] Similarly, repression of the endogenous HPV18 E6/E7 promoter in HeLa cells could be observed when E2 genes from bovine papillomavirus Type 1 (BPV1), HPV16 or 18 were introduced into HeLa cells. [20][21][22] Overexpression of E2 resulted in growth arrest or apoptosis of HPV-positive cervical cancer cells. [20][21][22] This was mainly due to the specific repression of the HPV promoter as the growth of HPV negative cells was not influenced by overexpression of E2. [20][21][22][23][24] In line with this, the reduction of E6/E7 mRNA levels resulted in an increase in E6 and E7 target protein levels such as p53, p21 and pRb. [20][21][22][23][24] E2 proteins bind as dimers to specific DNA sequences (E2 binding site, E2BS) to modulate transcription and viral DNA replication. The carboxyterminal domain which comprises 100 amino acids (aa) is sufficient for sequence-specific DNA recognition and dimerization 25 (Fig. 1). The E2 aminoterminal domain of...

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Section: E2c-ha Psg E8mentioning

confidence: 99%

The E8 repression domain can replace the E2 transactivation domain for growth inhibition of HeLa cells by papillomavirus E2 proteins

Stubenrauch

Straub

Fertey

et al. 2007

Intl Journal of Cancer

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“…CV-1 cells were cotransfected with 50 ng of pMEP-E2 constructs and 2.0 g of pBS1073, an E2-responsive luciferase reporter plasmid, and were assayed for luciferase activity as described in ref. 6.…”

Section: Methodsmentioning

confidence: 99%

“…Immunof luorescence was performed as described in ref. 6. Digital images were captured with a Leica TCS-SP2 laser scanning confocal imaging system.…”

Section: Methodsmentioning

confidence: 99%

Variations in the association of papillomavirus E2 proteins with mitotic chromosomes

Oliveira

Colf

McBride

2006

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

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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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“…Several different viruses target the individual BET proteins for a variety of purposes but often to regulate viral and cellular transcription (4,7,31,37,41,45,57,60). The papillomavirus E2 proteins bind to Brd4, and some utilize this interaction in tethering the viral genomes to mitotic chromosomes (1,3,57,59). The papillomavirus E2 transcriptional activation functions are also mediated through Brd4 (35,41,42).…”

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confidence: 99%

The Brd4 Extraterminal Domain Confers Transcription Activation Independent of pTEFb by Recruiting Multiple Proteins, Including NSD3

Rahman

Sowa

Ottinger

et al. 2011

Molecular and Cellular Biology

481

490

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Bromodomain protein 4 (Brd4) plays critical roles in development, cancer progression, and virus-host pathogenesis. To gain mechanistic insight into the various biological functions of Brd4, we performed a proteomic analysis to identify and characterize Brd4-associated cellular proteins. We found that the extraterminal (ET) domain, whose function has to date not been determined, interacts with NSD3, JMJD6, CHD4, GLTSCR1, and ATAD5. These ET-domain interactions were also conserved for Brd2 and Brd3, the other human BET proteins tested. We demonstrated that GLTSCR1, NSD3, and JMJD6 impart a pTEFb-independent transcriptional activation function on Brd4. NSD3 as well as JMJD6 is recruited to regulated genes in a Brd4-dependent manner. Moreover, we found that depletion of Brd4 or NSD3 reduces H3K36 methylation, demonstrating that the Brd4/NSD3 complex regulates this specific histone modification. Our results indicate that the Brd4 ET domain through the recruitment of the specific effectors regulates transcriptional activity. In particular, we show that one of these effectors, NSD3, regulates transcription by modifying the chromatin microenvironment at Brd4 target genes. Our study thus identifies the ET domain as a second important transcriptional regulatory domain for Brd4 in addition to the carboxyl-terminal domain (CTD) that interacts with pTEFb.One mechanism underlying the regulation of gene expression is the targeting of multiprotein complexes to modified histones, which then alters the chromatin microenvironment to stimulate or inhibit gene expression. The bromodomains and extraterminal (BET) domain family of proteins are characterized by the presence of two conserved domains, the tandem, amino-terminal bromodomains (BDI and BDII), which bind acetylated chromatin, and an extraterminal (ET) domain, whose function is unknown. The BET family is conserved from yeast to mammals and includes Saccharomyces cerevisiae bromodomain factor 1 (bdf1) and bromodomain factor 2 (bdf2), Drosophila melanogaster female sterile homeotic [fs(1)h], and mammalian Brd2, Brd3, Brd4, and testes/oocyte-specific BrdT/ Brd6. In yeast, deletion of bdf1 leads to a reduced growth rate and deletion of both bdf1 and bdf2 is lethal (27). Mutations of fs(1)h cause segmental abnormalities, including missing organs and homeotic transformations in the progeny of mutant females in Drosophila (13). Knockout of Brd4 or Brd2 in mice results in early embryonic lethality (18,21).The BET proteins have been shown to be important players in human disease, including viral infections and cancer. Several different viruses target the individual BET proteins for a variety of purposes but often to regulate viral and cellular transcription (4,7,31,37,41,45,57,60). The papillomavirus E2 proteins bind to Brd4, and some utilize this interaction in tethering the viral genomes to mitotic chromosomes (1,3,57,59). The papillomavirus E2 transcriptional activation functions are also mediated through Brd4 (35,41,42). With regard to human cancer, the Brd4-NUT and Brd3-NUT fusio...

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The Mitotic Chromosome Binding Activity of the Papillomavirus E2 Protein Correlates with Interaction with the Cellular Chromosomal Protein, Brd4

Cited by 110 publications

References 63 publications

The E8 repression domain can replace the E2 transactivation domain for growth inhibition of HeLa cells by papillomavirus E2 proteins

The E8 repression domain can replace the E2 transactivation domain for growth inhibition of HeLa cells by papillomavirus E2 proteins

Variations in the association of papillomavirus E2 proteins with mitotic chromosomes

The Brd4 Extraterminal Domain Confers Transcription Activation Independent of pTEFb by Recruiting Multiple Proteins, Including NSD3

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