TY - JOUR
T1 - C-Abl phosphorylates E6AP and regulates its E3 ubiquitin ligase activity
AU - Chan, Ai Leen
AU - Grossman, Tamar
AU - Zuckerman, Valentina
AU - Campigli Di Giammartino, Dafne
AU - Moshel, Ofra
AU - Scheffner, Martin
AU - Monahan, Brendon
AU - Pilling, Pat
AU - Jiang, Yong Hui
AU - Haupt, Sue
AU - Schueler-Furman, Ora
AU - Haupt, Ygal
PY - 2013/5/7
Y1 - 2013/5/7
N2 - In human papillomavirus (HPV)-infected cells, the p53 tumor suppressor is tightly regulated by the HPV-E6-E6AP complex, which promotes it for proteasomal degradation. We previously demonstrated that c-Abl tyrosine kinase protects p53 from HPV-E6-E6AP complex-mediated ubiquitination and degradation under stress conditions. However, the underlying mechanism was not defined. In this study, we explored the possibility that c-Abl targets E6AP and thereby protects p53. We demonstrated that c-Abl interacts with and phosphorylates E6AP. We determined that the E3 ligase activity of E6AP is impaired in response to phosphorylation by c-Abl. We mapped the phosphorylation site to tyrosine 636 within the HECT catalytic domain of E6AP, and using substitution mutants, we showed that this residue dictates the E3 ligase activity of E6AP, in a substrate-specific manner. On the basis of the crystal structure of the HECT domain of E6AP, we propose a model in which tyrosine 636 plays a regulatory role in the oligomerization of E6AP, which is a process implicated in its E3 ubiquitin ligase activity. Our results suggest that c-Abl protects p53 from HPV-E6-E6AP complex-mediated degradation by phosphorylating E6AP and impairing its E3 ligase activity, thus providing a molecular explanation for the stress-induced protection of p53 in HPV-infected cells.
AB - In human papillomavirus (HPV)-infected cells, the p53 tumor suppressor is tightly regulated by the HPV-E6-E6AP complex, which promotes it for proteasomal degradation. We previously demonstrated that c-Abl tyrosine kinase protects p53 from HPV-E6-E6AP complex-mediated ubiquitination and degradation under stress conditions. However, the underlying mechanism was not defined. In this study, we explored the possibility that c-Abl targets E6AP and thereby protects p53. We demonstrated that c-Abl interacts with and phosphorylates E6AP. We determined that the E3 ligase activity of E6AP is impaired in response to phosphorylation by c-Abl. We mapped the phosphorylation site to tyrosine 636 within the HECT catalytic domain of E6AP, and using substitution mutants, we showed that this residue dictates the E3 ligase activity of E6AP, in a substrate-specific manner. On the basis of the crystal structure of the HECT domain of E6AP, we propose a model in which tyrosine 636 plays a regulatory role in the oligomerization of E6AP, which is a process implicated in its E3 ubiquitin ligase activity. Our results suggest that c-Abl protects p53 from HPV-E6-E6AP complex-mediated degradation by phosphorylating E6AP and impairing its E3 ligase activity, thus providing a molecular explanation for the stress-induced protection of p53 in HPV-infected cells.
UR - http://www.scopus.com/inward/record.url?scp=84877347197&partnerID=8YFLogxK
U2 - 10.1021/bi301710c
DO - 10.1021/bi301710c
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C2 - 23581475
AN - SCOPUS:84877347197
SN - 0006-2960
VL - 52
SP - 3119
EP - 3129
JO - Biochemistry
JF - Biochemistry
IS - 18
ER -