TY - JOUR
T1 - Notch-dependent cell cycle arrest and apoptosis in mouse embryonic fibroblasts lacking Fbxw7
AU - Ishikawa, Y.
AU - Onoyama, I.
AU - Nakayama, K. I.
AU - Nakayama, K.
N1 - Funding Information:
We thank T Honjo for RbpjF/F mice; R Tsunematsu for an NICD1 plasmid; T Kitamura for pMX-puro and Plat-E cells; Y Ono and N Kobayashi for technical assistance; N Ishida and other laboratory members for helpful discussion. This study was supported in part by a Grant-in-Aid from the Ministry of Education, Culture, Sports, Science, and Technology of Japan and by the 21st Century Center of Excellence Program.
PY - 2008/10/16
Y1 - 2008/10/16
N2 - The F-box protein Fbxw7 mediates the ubiquitylation and consequent degradation of proteins that regulate cell cycle progression, including cyclin E, c-Myc, c-Jun and Notch. Moreover, certain human cancer cell lines harbor loss-of-function mutations in FBXW7 that result in excessive accumulation of Fbxw7 substrates, implicating Fbxw7 in tumor suppression. To elucidate the physiological function of Fbxw7, we conditionally ablated Fbxw7 in mouse embryonic fibroblasts (MEFs). Unexpectedly, loss of Fbxw7 induced cell cycle arrest and apoptosis that were accompanied by abnormal accumulation of the intracellular domain of Notch1 (NICD1). Forced expression of NICD1 in wild-type MEFs recapitulated the phenotype of the Fbxw7-deficient (Fbxw7 Δ/Δ) MEFs. Conversely, deletion of Rbpj normalized the phenotype of Fbxw7Δ/Δ MEFs, indicating that this phenotype is dependent on the Notch1-RBP-J signaling pathway. Deletion of the p53 gene prevented cell cycle arrest but not the induction of apoptosis in Fbxw7Δ/Δ cells. These observations suggest that Fbxw7 does not function as an oncosuppressor in MEFs. Instead, it promotes cell cycle progression and cell survival through degradation of Notch1, with loss of Fbxw7 resulting in NICD1 accumulation, cell cycle arrest and apoptosis.
AB - The F-box protein Fbxw7 mediates the ubiquitylation and consequent degradation of proteins that regulate cell cycle progression, including cyclin E, c-Myc, c-Jun and Notch. Moreover, certain human cancer cell lines harbor loss-of-function mutations in FBXW7 that result in excessive accumulation of Fbxw7 substrates, implicating Fbxw7 in tumor suppression. To elucidate the physiological function of Fbxw7, we conditionally ablated Fbxw7 in mouse embryonic fibroblasts (MEFs). Unexpectedly, loss of Fbxw7 induced cell cycle arrest and apoptosis that were accompanied by abnormal accumulation of the intracellular domain of Notch1 (NICD1). Forced expression of NICD1 in wild-type MEFs recapitulated the phenotype of the Fbxw7-deficient (Fbxw7 Δ/Δ) MEFs. Conversely, deletion of Rbpj normalized the phenotype of Fbxw7Δ/Δ MEFs, indicating that this phenotype is dependent on the Notch1-RBP-J signaling pathway. Deletion of the p53 gene prevented cell cycle arrest but not the induction of apoptosis in Fbxw7Δ/Δ cells. These observations suggest that Fbxw7 does not function as an oncosuppressor in MEFs. Instead, it promotes cell cycle progression and cell survival through degradation of Notch1, with loss of Fbxw7 resulting in NICD1 accumulation, cell cycle arrest and apoptosis.
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U2 - 10.1038/onc.2008.216
DO - 10.1038/onc.2008.216
M3 - Article
C2 - 18641686
AN - SCOPUS:54049087334
VL - 27
SP - 6164
EP - 6174
JO - Oncogene
JF - Oncogene
SN - 0950-9232
IS - 47
ER -