SCF-FBXO31 E3 Ligase Targets DNA Replication Factor Cdt1 for Proteolysis in the G2 Phase of Cell Cycle to Prevent Re-replication

• Published in: The Journal of biological chemistry 2014-06, Vol.289 (26), p.18514-18525
• Main Authors: Johansson, Pegah, Jeffery, Jessie, Al-Ejeh, Fares, Schulz, Renèe B., Callen, David F., Kumar, Raman, Khanna, Kum Kum
• Format: Article
• Language: English
• Subjects: Cdt1; Cell Cycle; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; DNA Replication; E3 Ubiquitin Ligase; F-Box Proteins - genetics; F-Box Proteins - metabolism; FBXO31; G2 Phase; Genomic Instability; Humans; Protein Binding; Protein Degradation; Protein Synthesis and Degradation; Proteolysis; Tumor Suppressor Proteins - genetics; Tumor Suppressor Proteins - metabolism; Ubiquitination
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M114.559930

FBXO31 was originally identified as a putative tumor suppressor gene in breast, ovarian, hepatocellular, and prostate cancers. By screening a set of cell cycle-regulated proteins as potential FBXO31 interaction partners, we have now identified Cdt1 as a novel substrate. Cdt1 DNA replication licensing factor is part of the pre-replication complex and essential for the maintenance of genomic integrity. We show that FBXO31 specifically interacts with Cdt1 and regulates its abundance by ubiquitylation leading to subsequent degradation. We also show that Cdt1 regulation by FBXO31 is limited to the G2 phase of the cell cycle and is independent of the pathways previously described for Cdt1 proteolysis in S and G2 phase. FBXO31 targeting of Cdt1 is mediated through the N terminus of Cdt1, a region previously shown to be responsible for its cell cycle regulation. Finally, we show that Cdt1 stabilization due to FBXO31 depletion results in re-replication. Our data present an additional pathway that contributes to the FBXO31 function as a tumor suppressor. Background: SCF E3 ligases regulate degradation of proteins involved in many processes including cell cycle progression and DNA repair. Results: SCF-FBXO31 interacts with and regulates the degradation of Cdt1 in G2 phase. Conclusion: FBXO31 regulates Cdt1 proteolysis during the G2 phase to prevent re-replication. Significance: SCF-FBXO31 regulation of Cdt1 is a novel pathway involved in the precise regulation of DNA replication.