Studies on the Phosphorylation of HPV16E7 Oncoprotein by DYRK1A
| Autor: | YUH-JIN LIANG, 梁毓津 |
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| Rok vydání: | 2008 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 96 HPV16, a high-risk tumorigenic virus, has been identified as one of the causative agents for the development of cervical cancer. Subsequent to viral infection, the constitutive expression of the viral oncoprotein E6 and oncoprotein E7 plays a number of critical roles in maintaining the transformed phenotype. Here we demonstrate that a cellular kinase, dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A), interacts with and phosphorylates HPV16E7 in vitro and in vivo. Using substitution mutations, we identified that DYRK1A specifically phosphorylates HPV16E7 at Thr5 and Thr7, which are located within the N-terminal CRI domain. This phosphorylation greatly increases the steady-state level of HPV16E7 by interfering with the protein’s 26S proteosome-dependent degradation. The half-life of E7 was extended significantly by replacing Thr5 and Thr7 with a phosphorylation mimetic residue, aspartic acid. In addition, DYRK1A-induced phosphorylation protected E7 from degradation and influenced E7’s function to modulate pRB degradation. We propose a new mechanism whereby DYRK1A phosphorylates Thr5 and Thr7 within HPV16E7. This phosphorylation then interferes with the degradation of HPV16E7, extending the protein half-life of HPV16E7 and increasing the colony-formation efficacy of HPV16E7. Our findings suggest that DYRK1A increases the transforming potential of HPV16-infected cells because of the greater stability of HPV16E7. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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