Competitive Binding to a Charged Leucine Motif Represses Transformation by a Papillomavirus E6 Oncoprotein

Bohl, Joanna; Das, Kingshuk; Dasgupta, B.; Pol, Scott B. Vande

doi:10.1006/viro.2000.0316

Cited by 40 publications

(40 citation statements)

References 17 publications

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“…E6 binding to MAML1 is potentially a key determinant of the ability of beta HPVs to replicate in skin, since Notch signaling in keratinocytes promotes differentiation and withdrawal from the cell cycle (41,51). We note that E6AP has been previously reported to bind BPV1 E6 (8,11,66), but we speculate that this interaction was likely due to overexpression of one binding partner or to in vitro artifacts and does not reflect physiological binding in a normal cellular environment.…”

Section: Discussionmentioning

confidence: 76%

Comprehensive Analysis of Host Cellular Interactions with Human Papillomavirus E6 Proteins Identifies New E6 Binding Partners and Reflects Viral Diversity

White

Kramer

Tan

et al. 2012

J Virol

182

240

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We have begun to define the human papillomavirus (HPV)-associated proteome for a subset of the more than 120 HPV types that have been identified to date. Our approach uses a mass spectrometry-based platform for the systematic identification of interactions between human papillomavirus and host cellular proteins, and here we report a proteomic analysis of the E6 proteins from 16 different HPV types. The viruses included represent high-risk, low-risk, and non-cancer-associated types from genus alpha as well as viruses from four different species in genus beta. The E6 interaction data set consists of 153 cellular proteins, including several previously reported HPV E6 interactors such as p53, E6AP, MAML1, and p300/CBP and proteins containing PDZ domains. We report the genus-specific binding of E6s to either E6AP or MAML1, define the specific HPV E6s that bind to p300, and demonstrate several new features of interactions involving beta HPV E6s. In particular, we report that several beta HPV E6s bind to proteins containing PDZ domains and that at least two beta HPV E6s bind to p53. Finally, we report the newly discovered interaction of proteins of E6 of beta genus, species 2, with the Ccr4-Not complex, the first report of a viral protein binding to this complex. This data set represents a comprehensive survey of E6 binding partners that provides a resource for the HPV field and will allow continued studies on the diverse biology of the human papillomaviruses.T he human papillomaviruses (HPVs) comprise more than 120 different virus types, each with a double-stranded DNA genome of approximately 8 kb. The HPVs have similar genome organizations, with regulatory functions encoded by the early (E) genes and structural components encoded by the late (L) genes (reviewed in reference 24). HPVs of different types differ in DNA sequences by 10% or more in the L1 gene, and the other viral genes exhibit a greater degree of sequence diversity between types (6, 15). Papillomaviruses are grouped into genera based on their L1 gene sequences and are further subdivided into species, with most of the HPVs in genus alpha or genus beta. The genus alpha HPVs infect the mucosal epithelium, and those that are the etiological agent responsible for the development of anogenital cancers (including cervical cancer) fall into genus alpha, species 7, and genus alpha, species 9. Beta-type HPVs infect the cutaneous epithelium.The HPV E6 protein has long been appreciated as a critical regulator of the viral life cycle and driver of tumorigenesis for the high-risk HPVs. Through the action of the HPV E7 protein, the G 1 -S checkpoint is bypassed in infected cells by the inactivation of the retinoblastoma tumor suppressor protein (pRB1) (17,18,46). This results in a cellular environment that is conducive to the replication of the viral DNA but in which proapoptotic signals have been triggered. One crucial function of high-risk HPV E6 proteins is to counteract the effects of p53 following this trigger, and this is accomplished by the targeted ubiquitylati...

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Section: Discussionmentioning

confidence: 76%

Comprehensive Analysis of Host Cellular Interactions with Human Papillomavirus E6 Proteins Identifies New E6 Binding Partners and Reflects Viral Diversity

White

Kramer

Tan

et al. 2012

J Virol

182

240

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“…Murine C127 and paxillin-null MEFs were maintained in Dulbecco modified Eagle medium supplemented with 10% fetal calf serum; assays for anchorage-independent cell growth were performed as previously described (1).…”

Section: Methodsmentioning

confidence: 99%

“…Glutathione S-transferase (GST) and maltose-binding protein (MBP) fusions to BE6 and paxillin and paxillin mutants have been previously described (30). MBP and GST fusions were expressed in Escherichia coli strain BL21(DE3)-RIL and purified onto amylose-Sepharose or glutathione-Sepharose beads as described previously (1).…”

Section: Methodsmentioning

confidence: 99%

“…Anogenital type human papillomavirus (HPV) E6 oncoproteins and E6 from bovine papillomavirus type 1 (BE6) interact with cellular proteins by binding to an eight-amino-acid peptide displayed on the target protein (XLXXLLXX, abbreviated LXXLL here) (3,7,10,30); this interaction is required for cellular transformation by BE6 (1,30). While anogenital HPV E6 proteins bind to a LXXLL motif on the ubiquitin ligase E6AP, BE6 binds to LXXLL motifs found on the cellular adapter protein paxillin, while HPV-16 E6 binds paxillin poorly (26,30).…”

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confidence: 99%

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Transformation by Bovine Papillomavirus Type 1 E6 Requires Paxillin

Wade

Brimer

Pol

2008

J Virol

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Papillomavirus E6 proteins are adapters that change the function of cellular regulatory proteins. The bovine papillomavirus type 1 E6 (BE6) binds to LXXLL peptide sequences termed LD motifs (consensus sequence LDXLLXXL) on the cellular protein paxillin that is a substrate of Src and focal adhesion kinases. Anchorageindependent transformation induced by BE6 required both paxillin and BE6-binding LD motifs on paxillin but was independent of the major tyrosine phosphorylation sites of paxillin. The essential role of paxillin in transformation by BE6 highlights the role of paxillin in the transduction of cellular signals that result in anchorage-independent cell proliferation.Anogenital type human papillomavirus (HPV) E6 oncoproteins and E6 from bovine papillomavirus type 1 (BE6) interact with cellular proteins by binding to an eight-amino-acid peptide displayed on the target protein (XLXXLLXX, abbreviated LXXLL here) (3,7,10,30); this interaction is required for cellular transformation by BE6 (1, 30). While anogenital HPV E6 proteins bind to a LXXLL motif on the ubiquitin ligase E6AP, BE6 binds to LXXLL motifs found on the cellular adapter protein paxillin, while HPV-16 E6 binds paxillin poorly (26,30).Paxillin was first identified as a hyperphosphorylated protein in Src transformed cells. It localizes to focal adhesions and associates with focal adhesion proteins implicated in the regulation of cell attachment, spreading, and migration, including focal adhesion kinase (FAK), GIT1, PAK, Src, and Crk (reviewed in reference 6 and illustrated in Fig. 1). Paxillin tyrosine phosphorylation sites bind to the SH2-containing proteins Src (at Y31) and CRKL (at Y118). Paxillin also contains five copies of a peptide motif termed LD1 through LD5 (consensus LXXLLXXL) that serve as binding sites for cellular proteins; LD1 interacts with acropaxin and ILK (16, 17), LD2 interacts with FAK and vinculin, LD4 interacts with GIT1 and FAK (29), and the LD3 and LD5 interaction partners remain uncharacterized, although LD5 is functionally required to support FAK tyrosine phosphorylation in embryonic stem (ES) cells (32). LD motifs also bind the BE6 oncoprotein (26, 30). The carboxy terminus of paxillin contains four LIM domains: LIM2 and -3 localize paxillin to focal adhesions (5, 32), and LIM1, -2, and -3 support the tyrosine phosphorylation of FAK in ES cells (32). LIM4 interacts with the tyrosine phosphatase PTP-PEST (8, 21).Paxillin regulates focal adhesion turnover, since cells from which paxillin has been deleted or that express paxillin mutants have delayed focal adhesion turnover and cell migration (33, 34), and paxillin has been shown to influence the activity of proteins, including the Rho family of small GTP-binding proteins that are involved in regulating actin dynamics (reviewed in references 19 and 35). HIC-5 is a paxillin family member that is highly similar to paxillin but differs in its binding to FAK and GIT proteins and is differentially expressed in differentiated tissues and in response to morphogenic signaling (14,...

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“…C127 cells were reported to contain wild-type p53 (Murphy et al, 1996). Unlike the high-risk HPV E6, BPV-1 E6 does not bind p53 , although it does bind the ubiquitin-protein ligase E6AP that forms a complex with high-risk HPV E6 to degrade p53 (Chen et al, 1995;Bohl et al, 2000). To assess the role of p53 in BPV-1 oncogenes-modulated apoptosis, we established stable cell lines expressing BPV-1 E7 (10.1 PBE7), and E6 plus E7 (10.1 PBE6E7) in the p53À/À mouse fibroblast cell line 10.1 (Murphy et al, 1996).…”

Section: Modulatory Effects Of Bpv-1 E6 and E7 On Fas-mediated Apoptomentioning

confidence: 99%

Opposing effects of bovine papillomavirus type 1 E6 and E7 genes on Fas-mediated apoptosis

Liu

Gao

et al. 2005

Oncogene

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Programmed cell death (PCD), best exemplified by apoptosis, is a genetically programmed process of cellular destruction that is indispensable for normal development and homeostasis of multicellular organisms. Tumor necrosis factor a (TNF) and related cytokines are employed by host defenses to eliminate virally infected cells through induction of apoptosis. Many viruses have evolved specific gene products to modulate this process. We have recently shown that the bovine papillomavirus type 1 (BPV-1) E6 and E7 genes independently sensitize mouse cells to TNF-induced apoptosis. In this report, we investigated the effect of E6 and E7 expression on Fasmediated apoptosis. In contrast to TNF-mediated apoptosis, E6 and E7 demonstrated opposite effects: while E7 potentiated apoptosis triggered by an agonistic Fas antibody, E6 attenuated the effect. The mitochondrial pathway leading to the activation of caspases appears to be involved in Fas-mediated apoptosis in C127 cells. To further explore the mechanisms by which E6 and E7 modulate Fas-mediated apoptosis, we examined the surface expression of Fas in cells expressing E6 and E7. Significantly, levels of surface Fas expression correlated with the opposing effects of E6 and E7 on Fas-mediated apoptosis. Specifically, while E7 increased the surface expression of Fas, E6 reduced surface Fas expression. Mutational analysis demonstrated a correlation of E6's ability to downregulate surface Fas expression and apoptosis. Since the tumor suppressor p53 can be targeted for degradation by human papillomavirus and has been shown to induce apoptosis by upregulating surface Fas expression, we investigated the role of p53 in BPV-1 E6 and E7 modulation of Fas-mediated apoptosis. Our results demonstrated that the modulatory effects by E6 and E7 could occur in the absence of p53. Interestingly, the reduced Fas protein level on the cell surface is not accompanied by a decrease in total Fas levels in E6-expressing cells. Instead, considerably more Fas protein is found in the cytoplasm of cells expressing E6. These results highlight a novel activity of E6 and E7 that may be involved in viral pathogenesis.

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Competitive Binding to a Charged Leucine Motif Represses Transformation by a Papillomavirus E6 Oncoprotein

Cited by 40 publications

References 17 publications

Comprehensive Analysis of Host Cellular Interactions with Human Papillomavirus E6 Proteins Identifies New E6 Binding Partners and Reflects Viral Diversity

Comprehensive Analysis of Host Cellular Interactions with Human Papillomavirus E6 Proteins Identifies New E6 Binding Partners and Reflects Viral Diversity

Transformation by Bovine Papillomavirus Type 1 E6 Requires Paxillin

Opposing effects of bovine papillomavirus type 1 E6 and E7 genes on Fas-mediated apoptosis

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