Skp2-Mediated Stabilization of MTH1 Promotes Survival of Melanoma Cells upon Oxidative Stress

• Published in: Cancer research (Chicago, Ill.) Vol. 77; no. 22; pp. 6226 - 6239
• Main Authors: Wang, Jia Yu, Liu, Guang Zhi, Wilmott, James S, La, Ting, Feng, Yu Chen, Yari, Hamed, Yan, Xu Guang, Thorne, Rick F, Scolyer, Richard A, Zhang, Xu Dong, Jin, Lei
• Format: Journal Article
• Language: English
• Published: United States American Association for Cancer Research, Inc 15.11.2017
• Subjects: Apoptosis; Blotting, Western; Cancer; Cell Line; Cell Line, Tumor; Cell Survival - genetics; Cullin; Damage prevention; DNA damage; DNA Repair Enzymes - genetics; DNA Repair Enzymes - metabolism; Gene Expression Regulation, Neoplastic; Humans; MAP kinase; MAP Kinase Signaling System - genetics; Melanoma; Melanoma - genetics; Melanoma - metabolism; Melanoma - pathology; Oxidative Stress; Phosphoric Monoester Hydrolases - genetics; Phosphoric Monoester Hydrolases - metabolism; Polyubiquitin - metabolism; Protein Stability; Reactive oxygen species; Reverse Transcriptase Polymerase Chain Reaction; RNA Interference; S-Phase Kinase-Associated Proteins - genetics; S-Phase Kinase-Associated Proteins - metabolism; Skp2 protein; Therapeutic targets; Ubiquitin; Ubiquitin-protein ligase; Ubiquitination
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/0008-5472.can-17-1965

MTH1 helps prevent misincorporation of ROS-damaged dNTPs into genomic DNA; however, there is little understanding of how MTH1 itself is regulated. Here, we report that MTH1 is regulated by polyubiquitination mediated by the E3 ligase Skp2. In melanoma cells, MTH1 was upregulated commonly mainly due to its improved stability caused by K63-linked polyubiquitination. Although Skp2 along with other components of the Skp1-Cullin-F-box (SCF) ubiquitin ligase complex was physically associated with MTH1, blocking the SCF function ablated MTH1 ubiquitination and expression. Conversely, overexpressing Skp2-elevated levels of MTH1 associated with an increase in its K63-linked ubiquitination. In melanoma cell lines and patient specimens, we observed a positive correlation of Skp2 and MTH1 expression. Mechanistic investigations showed that Skp2 limited DNA damage and apoptosis triggered by oxidative stress and that MAPK upregulated Skp2 and MTH1 to render cells more resistant to such stress. Collectively, our findings identify Skp2-mediated K63-linked polyubiquitination as a critical regulatory mechanism responsible for MTH1 upregulation in melanoma, with potential implications to target the MAPK/Skp2/MTH1 pathway to improve its treatment. .