Cyclin F-Dependent Degradation of RBPJ Inhibits IDH1-Mediated Tumorigenesis.

Cyclin F is a substrate recognition subunit of Skp1-Cul1-F-box protein (SCF) E3 ubiquitin ligase complex. Although there have been reports describing the role of cyclin F in the genotoxic stress response, its function under conditions of altered metabolic homeostasis remain unexplored. Here we report that is induced upon metabolic stress in a FOXO1-dependent manner. Under metabolic stress conditions, cyclin F mediated polyubiquitylation of RBPJ at Lys315, leading to its proteasomal degradation. RBPJ regulated the expression of IDH1, which is often mutated to an oncogenic form IDH1 in cancers. Thus, metabolic stress-induced cyclin F attenuated the oncogenic functions of IDH1 in an RBPJ-dependent manner. Studies in mouse tumor models indicated that abrogation of cyclin F expression facilitates IDH1-mediated tumorigenesis and metastasis. In addition, increased IDH1 levels correlated with reduced cyclin F levels in increasing grades of glioma. These findings highlight a novel aspect of cyclin F functions in inhibiting tumorigenesis and provide mechanistic insights into regulation of These findings reveal mechanistic insights into the key role of the cyclin F-RBPJ axis in response to metabolic stress in cancer cells. .