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  • 1
    Keywords: APOPTOSIS ; PROTEIN ; INDUCTION ; ASSOCIATION ; CERVICAL-CANCER ; p53 ; POSITIVE CANCER-CELLS ; NUCLEAR-LOCALIZATION ; E6-MEDIATED DEGRADATION ; AGGRESOMES
    Abstract: Oncogenic types of human papillomaviruses (HPVs) cause cervical cancer and other malignancies in humans. The HPV E6 oncoprotein is considered to be an attractive therapeutic target since its inhibition can lead to the apoptotic cell death of HPV-positive cancer cells. The HPV type 16 (HPV16) E6-binding peptide pep11, and variants thereof, induce cell death specifically in HPV16-positive cancer cells. Although they do not encompass the LxxLL binding motif found in cellular HPV16 E6 interaction partners, such as E6AP, the pep11 variants strongly bind to HPV16 E6 by contacting the recently identified E6AP binding pocket. Thus, these peptides can serve as prototype E6-inhibitory molecules which target the E6AP pocket. We here analyzed their intracellular interaction with HPV16 E6. By comprehensive intracellular binding studies and GST pull-down assays, we show that E6-binding competent pep11 variants induce the formation of a trimeric complex, consisting of pep11, HPV16 E6 and p53. These findings indicate that peptides, which do not contain the LxxLL motif, can reshape E6 to enable its interaction with p53. The formation of the trimeric HPV16 E6 / peptide / p53 complex was associated with an increase of endogenous HPV16 E6 protein amounts. Yet, total cellular p53 amounts were also increased, indicating that the E6 / E6AP-mediated degradation of p53 is blocked. These findings suggest that inhibition of oncogenic activities by targeting the E6AP pocket on HPV16 E6 could be a strategy for therapeutic intervention.
    Type of Publication: Journal article published
    PubMed ID: 26151636
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  • 2
    Abstract: The HPV E6 oncoprotein maintains the malignant phenotype of HPV-positive cancer cells and represents an attractive therapeutic target. E6 forms a complex with the cellular E6AP ubiquitin ligase, ultimately leading to p53 degradation. The recently elucidated x-ray structure of a HPV16 E6/E6AP complex showed that HPV16 E6 forms a distinct binding pocket for E6AP. This discovery raises the question whether the E6AP binding pocket is druggable, i. e. whether it provides a docking site for functional E6 inhibitors. To address these issues, we performed a detailed analysis of the HPV16 E6 interactions with two small peptides: (i) E6APpep, corresponding to the E6 binding domain of E6AP, and (ii) pep11**, a peptide that binds to HPV16 E6 and, in contrast to E6APpep, induces apoptosis, specifically in HPV16-positive cancer cells. Surface plasmon resonance, NMR chemical shift perturbation, and mammalian two-hybrid analyses coupled to mutagenesis indicate that E6APpep contacts HPV16 E6 amino acid residues within the E6AP pocket, both in vitro and intracellularly. Many of these amino acids were also important for binding to pep11**, suggesting that the binding sites for the two peptides on HPV16 E6 overlap. Yet, few E6 amino acids were differentially involved which may contribute to the higher binding affinity of pep11**. Data from the HPV16 E6/pep11** interaction allowed the rational design of single amino acid exchanges in HPV18 and HPV31 E6 that enabled their binding to pep11**. Taken together, these results suggest that E6 molecular surfaces mediating E6APpep binding can also accommodate pro-apoptotic peptides that belong to different sequence families. As proof of concept, this study provides the first experimental evidence that the E6AP binding pocket is druggable, opening new possibilities for rational, structure-based drug design.
    Type of Publication: Journal article published
    PubMed ID: 25383876
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  • 3
    Publication Date: 2011-07-15
    Description: Many cellular functions involve multi-domain proteins, which are composed of structurally independent modules connected by flexible linkers. Although it is often well understood how a given domain recognizes a cognate oligonucleotide or peptide motif, the dynamic interaction of multiple domains in the recognition of these ligands remains to be characterized. Here we have studied the molecular mechanisms of the recognition of the 3'-splice-site-associated polypyrimidine tract RNA by the large subunit of the human U2 snRNP auxiliary factor (U2AF65) as a key early step in pre-mRNA splicing. We show that the tandem RNA recognition motif domains of U2AF65 adopt two remarkably distinct domain arrangements in the absence or presence of a strong (that is, high affinity) polypyrimidine tract. Recognition of sequence variations in the polypyrimidine tract RNA involves a population shift between these closed and open conformations. The equilibrium between the two conformations functions as a molecular rheostat that quantitatively correlates the natural variations in polypyrimidine tract nucleotide composition, length and functional strength to the efficiency to recruit U2 snRNP to the intron during spliceosome assembly. Mutations that shift the conformational equilibrium without directly affecting RNA binding modulate splicing activity accordingly. Similar mechanisms of cooperative multi-domain conformational selection may operate more generally in the recognition of degenerate nucleotide or amino acid motifs by multi-domain proteins.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mackereth, Cameron D -- Madl, Tobias -- Bonnal, Sophie -- Simon, Bernd -- Zanier, Katia -- Gasch, Alexander -- Rybin, Vladimir -- Valcarcel, Juan -- Sattler, Michael -- England -- Nature. 2011 Jul 13;475(7356):408-11. doi: 10.1038/nature10171.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Structural Biology, Helmholtz Zentrum Munchen, Ingolstadter Landstrasse 1, 85764 Neuherberg, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21753750" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Motifs ; Base Sequence ; Humans ; Introns/genetics ; Ligands ; Models, Molecular ; Mutation ; Nuclear Magnetic Resonance, Biomolecular ; Nuclear Proteins/*chemistry/*metabolism ; Protein Binding ; Protein Structure, Tertiary ; Pyrimidines/metabolism ; RNA Precursors/*genetics/*metabolism ; RNA Splice Sites/genetics ; RNA Splicing/*physiology ; RNA, Messenger/genetics/*metabolism ; Ribonucleoproteins/*chemistry/*metabolism ; Spliceosomes/chemistry/metabolism ; Substrate Specificity
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2016-01-21
    Description: The p53 pro-apoptotic tumour suppressor is mutated or functionally altered in most cancers. In epithelial tumours induced by 'high-risk' mucosal human papilloma viruses, including human cervical carcinoma and a growing number of head-and-neck cancers, p53 is degraded by the viral oncoprotein E6 (ref. 2). In this process, E6 binds to a short leucine (L)-rich LxxLL consensus sequence within the cellular ubiquitin ligase E6AP. Subsequently, the E6/E6AP heterodimer recruits and degrades p53 (ref. 4). Neither E6 nor E6AP are separately able to recruit p53 (refs 3, 5), and the precise mode of assembly of E6, E6AP and p53 is unknown. Here we solve the crystal structure of a ternary complex comprising full-length human papilloma virus type 16 (HPV-16) E6, the LxxLL motif of E6AP and the core domain of p53. The LxxLL motif of E6AP renders the conformation of E6 competent for interaction with p53 by structuring a p53-binding cleft on E6. Mutagenesis of critical positions at the E6-p53 interface disrupts p53 degradation. The E6-binding site of p53 is distal from previously described DNA- and protein-binding surfaces of the core domain. This suggests that, in principle, E6 may avoid competition with cellular factors by targeting both free and bound p53 molecules. The E6/E6AP/p53 complex represents a prototype of viral hijacking of both the ubiquitin-mediated protein degradation pathway and the p53 tumour suppressor pathway. The present structure provides a framework for the design of inhibitory therapeutic strategies against oncogenesis mediated by human papilloma virus.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Martinez-Zapien, Denise -- Ruiz, Francesc Xavier -- Poirson, Juline -- Mitschler, Andre -- Ramirez, Juan -- Forster, Anne -- Cousido-Siah, Alexandra -- Masson, Murielle -- Vande Pol, Scott -- Podjarny, Alberto -- Trave, Gilles -- Zanier, Katia -- R01CA134737/CA/NCI NIH HHS/ -- England -- Nature. 2016 Jan 28;529(7587):541-5. doi: 10.1038/nature16481. Epub 2016 Jan 20.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Equipe labellisee Ligue, Biotechnologie et signalisation cellulaire UMR 7242, Ecole Superieure de Biotechnologie de Strasbourg, Boulevard Sebastien Brant, BP 10413, F-67412 Illkirch, France. ; Institut de Genetique et de Biologie Moleculaire et Cellulaire (IGBMC)/INSERM U964/CNRS UMR 7104/Universite de Strasbourg, 1 rue Laurent Fries, BP 10142, F-67404 Illkirch, France. ; Department of Pathology, University of Virginia, PO Box 800904, Charlottesville, Virginia 22908-0904, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26789255" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Motifs ; Amino Acid Sequence ; Binding Sites ; Crystallography, X-Ray ; Human papillomavirus 16/chemistry/*metabolism/pathogenicity ; Humans ; Models, Biological ; Models, Molecular ; Molecular Sequence Data ; Mutant Proteins/chemistry/metabolism ; Oncogene Proteins, Viral/*chemistry/genetics/*metabolism ; Protein Binding ; Protein Structure, Tertiary ; *Proteolysis ; Repressor Proteins/*chemistry/genetics/*metabolism ; Tumor Suppressor Protein p53/*chemistry/genetics/*metabolism ; Ubiquitin-Protein Ligases/*chemistry
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2013-02-09
    Description: E6 viral oncoproteins are key players in epithelial tumors induced by papillomaviruses in vertebrates, including cervical cancer in humans. E6 proteins target many host proteins by specifically interacting with acidic LxxLL motifs. We solved the crystal structures of bovine (BPV1) and human (HPV16) papillomavirus E6 proteins bound to LxxLL peptides from the focal adhesion protein paxillin and the ubiquitin ligase E6AP, respectively. In both E6 proteins, two zinc domains and a linker helix form a basic-hydrophobic pocket, which captures helical LxxLL motifs in a way compatible with other interaction modes. Mutational inactivation of the LxxLL binding pocket disrupts the oncogenic activities of both E6 proteins. This work reveals the structural basis of both the multifunctionality and the oncogenicity of E6 proteins.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3899395/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3899395/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zanier, Katia -- Charbonnier, Sebastian -- Sidi, Abdellahi Ould M'hamed Ould -- McEwen, Alastair G -- Ferrario, Maria Giovanna -- Poussin-Courmontagne, Pierre -- Cura, Vincent -- Brimer, Nicole -- Babah, Khaled Ould -- Ansari, Tina -- Muller, Isabelle -- Stote, Roland H -- Cavarelli, Jean -- Vande Pol, Scott -- Trave, Gilles -- CA08093/CA/NCI NIH HHS/ -- CA120352/CA/NCI NIH HHS/ -- CA134737/CA/NCI NIH HHS/ -- P30 CA044579/CA/NCI NIH HHS/ -- R01 CA134737/CA/NCI NIH HHS/ -- R01CA134737/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 2013 Feb 8;339(6120):694-8. doi: 10.1126/science.1229934.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Biotechnologie et Signalisation Cellulaire UMR 7242, Ecole Superieure de Biotechnologie de Strasbourg, Boulevard Sebastien Brant, BP 10413, F-67412 Illkirch, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23393263" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Motifs ; Amino Acid Sequence ; Bovine papillomavirus 1 ; Crystallography, X-Ray ; Human papillomavirus 16 ; Humans ; Hydrophobic and Hydrophilic Interactions ; Models, Molecular ; Molecular Dynamics Simulation ; Molecular Sequence Data ; Oncogene Proteins, Viral/*chemistry/genetics/*metabolism ; Paxillin/*chemistry/metabolism ; Peptide Fragments/chemistry/metabolism ; Point Mutation ; *Protein Interaction Domains and Motifs ; Protein Structure, Secondary ; Repressor Proteins/*chemistry/genetics/*metabolism ; Ubiquitin-Protein Ligases/*chemistry/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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