High-risk HPV E6 oncoproteins assemble into large oligomers that allow localization of endogenous species in prototypic HPV-transformed cell lines
| Autor: | Maria Garcia-Alai, Clara Smal, Lía I. Pietrasanta, Gonzalo de Prat-Gay, Karina I Dantur |
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| Rok vydání: | 2007 |
| Předmět: |
Protein Folding
PDZ domain Uterine Cervical Neoplasms Biology Biochemistry DNA-binding protein Models Biological Epitope law.invention Protein structure law Humans Protein Structure Quaternary Cell Line Transformed Human papillomavirus 16 Base Sequence Human papillomavirus 18 Oncogene Proteins Viral Cell Transformation Viral Molecular biology Cell biology DNA-Binding Proteins Repressor Proteins Cell Transformation Neoplastic Cytoplasm Multiprotein Complexes DNA Viral Recombinant DNA Protein folding Female Tumor Suppressor Protein p53 Nuclear localization sequence |
| Zdroj: | Biochemistry. 46(2) |
| ISSN: | 0006-2960 |
| Popis: | The E6 oncoproteins of high-risk HPV types 16 and 18 are involved in the development of cervical cancer. Besides its determinant role in carcinogenic progression, HPV E6 oncoprotein has also been instrumental in elucidating fundamental aspects of p53 function and its ubiquitin-proteasome degradation, with counterpart activities in various DNA tumor viruses. Establishing the conformational state and cellular distribution unequivocally for the endogenous protein in HPV-transformed cell lines derived from carcinomas is essential for understanding the underlying mechanism. Recombinant E6 from high-risk strains 16 and 18 folds into soluble oligomers of approximately 1.2 MDa, which are thermostable and display cooperative loss of tertiary and secondary structure upon chemical denaturation. Antibodies raised against these assemblies locate E6 evenly distributed in the cells. By depleting the polyclonal serum by immunoblocking with monomeric E6, the nuclei of Hela and CaSki cells become completely devoid of label, indicating that monomeric species are mainly localized in the nucleus and that both monomers and oligomers share epitopes. The monomeric species promote degradation of p53 by the proteasome, which correlates with the nuclear localization we describe. In contrast, the oligomeric E6 does not promote p53 degradation, in agreement with its cytoplasmic localization inferred from the immunoneutralization experiments. Our results indicate that the cytoplasmic species contain conformational epitopes that may arise from yet undefined homo or hetero-oligomers, but its localization otherwise agrees with that of the other group of major E6 targets, those involving PDZ binding domains, which requires further investigation. |
| Databáze: | OpenAIRE |
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