VprBP/DCAF1 Regulates the Degradation and Nonproteolytic Activation of the Cell Cycle Transcription Factor FoxM1

• Published in: Molecular and cellular biology Vol. 37; no. 13
• Main Authors: Wang, Xianxi, Arceci, Anthony, Bird, Kelly, Mills, Christine A., Choudhury, Rajarshi, Kernan, Jennifer L., Zhou, Chunxiao, Bae-Jump, Victoria, Bowers, Albert, Emanuele, Michael J.
• Format: Journal Article
• Language: English
• Published: United States Taylor & Francis 01.07.2017; American Society for Microbiology
• Subjects: Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell Cycle; Chromosomal Instability; cullin ring ligase; Cystadenocarcinoma, Serous - genetics; Cystadenocarcinoma, Serous - metabolism; Cystadenocarcinoma, Serous - pathology; Female; Forkhead Box Protein M1 - genetics; Forkhead Box Protein M1 - metabolism; FoxM1; Gene Expression Regulation, Neoplastic; Humans; Ovarian Neoplasms - genetics; Ovarian Neoplasms - metabolism; Ovarian Neoplasms - pathology; Protein Serine-Threonine Kinases; Proteolysis; transcriptional regulation; Tumor Cells, Cultured; Ubiquitin-Protein Ligases - genetics; Ubiquitin-Protein Ligases - metabolism; Ubiquitination; cullin ring ligase; cell cycle; ubiquitination; FoxM1; transcriptional regulation
• ISSN: 1098-5549; 0270-7306; 1098-5549
• DOI: 10.1128/MCB.00609-16

The oncogenic transcription factor FoxM1 plays a vital role in cell cycle progression, is activated in numerous human malignancies, and is linked to chromosome instability. We characterize here a cullin 4-based E3 ubiquitin ligase and its substrate receptor, VprBP/DCAF1 (CRL4 VprBP ), which we show regulate FoxM1 ubiquitylation and degradation. Paradoxically, we also found that the substrate receptor VprBP is a potent FoxM1 activator. VprBP depletion reduces expression of FoxM1 target genes and impairs mitotic entry, whereas ectopic VprBP expression strongly activates a FoxM1 transcriptional reporter. VprBP binding to CRL4 is reduced during mitosis, and our data suggest that VprBP activation of FoxM1 is ligase independent. This implies a nonproteolytic activation mechanism that is reminiscent of, yet distinct from, the ubiquitin-dependent transactivation of the oncoprotein Myc by other E3s. Significantly, VprBP protein levels were upregulated in high-grade serous ovarian patient tumors, where the FoxM1 signature is amplified. These data suggest that FoxM1 abundance and activity are controlled by VprBP and highlight the functional repurposing of E3 ligase substrate receptors independent of the ubiquitin system.