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HPV-18 E6*I modulates HPV-18 full-length E6 functions in a cell cycle dependent manner
Ernesto Guccione1, David Pim, Lawrence Banks
1International Centre for Genetic Engineering and Biotechnology, Padriciano 99, I-34012 Trieste, Italy.
International Journal of Cancer
|June 2, 2004
Summary
The Human Papillomavirus (HPV) E6*I protein fine-tunes the full-length E6 protein
Area of Science:
- Oncology
- Virology
- Molecular Biology
Background:
- High-risk Human Papillomavirus (HPV) Types 16 and 18 E6 open reading frames (ORFs) encode truncated E6* proteins.
- HPV-18 E6*I interacts with full-length E6 and E6-AP, inhibiting p53 degradation and exhibiting antiproliferative effects in cervical cancer cells.
Purpose of the Study:
- To investigate the modulatory functions of HPV-18 E6*I on full-length HPV-18 E6.
- To analyze the sub-cellular distribution and cell cycle-dependent abundance of E6 and E6*I.
- To determine the impact of E6*I overexpression on E6 target proteins and E6 cellular localization.
Main Methods:
- Epitope-tagged protein analysis
- Sub-cellular distribution studies
- Cell cycle analysis
- Western blotting
- Proteasome inhibitor treatment
Main Results:
- HPV-18 E6*I is upregulated during G2/M phase.
- E6*I overexpression increases p53, hDlg, and Scribble levels, particularly during G2/M.
- E6*I overexpression reduces E6 in insoluble nuclear and membrane fractions.
- Proteasome inhibition restores E6 levels, indicating E6/E6*I interaction causes E6 destabilization.
Conclusions:
- HPV-18 E6*I acts as a fine regulator of full-length E6.
- E6*I modulates E6's cellular abundance and distribution during the cell cycle via direct interaction.
- This interaction leads to E6 protein destabilization and altered target protein expression.