2. Academic Validation
  3. USP7 is a novel Deubiquitinase sustaining PLK1 protein stability and regulating chromosome alignment in mitosis

USP7 is a novel Deubiquitinase sustaining PLK1 protein stability and regulating chromosome alignment in mitosis

  • J Exp Clin Cancer Res. 2019 Nov 15;38(1):468. doi: 10.1186/s13046-019-1457-8.
Yuchong Peng 1 2,  Youhong Liu 1 2,  Yingxue Gao 1 2,  Bowen Yuan 3,  Xuli Qi 1 2,  Yuxin Fu 1 2,  Qianling Zhu 1 2,  Tuoyu Cao 1 2,  Songwei Zhang 1 2,  Linglong Yin 1 2,  Xiong Li 4 5 6 7
Affiliations

Affiliations

  • 1 Center for Molecular Medicine, Xiangya Hospital, Central South University, Changsha, China.
  • 2 Hunan Key Laboratory of Molecular Radiation Oncology, Xiangya Hospital, Central South University, Changsha, China.
  • 3 Department of Pathology, The Third Xiangya Hospital, Central South University, Changsha, China.
  • 4 Center for Molecular Medicine, Xiangya Hospital, Central South University, Changsha, China. [email protected].
  • 5 Hunan Key Laboratory of Molecular Radiation Oncology, Xiangya Hospital, Central South University, Changsha, China. [email protected].
  • 6 School of Clinical Pharmacy, Guangdong Pharmacology University, Guangzhou, China. [email protected].
  • 7 The First Affiliated Hospital, Guangdong Pharmacology University, 19 Nonglinxia Road, Yuexiu District, Guangzhou, Guangdong, China. [email protected].
PMID: 31730000 DOI: 10.1186/s13046-019-1457-8
Abstract

Background: The Deubiquitinase USP7 has been identified as an oncogene with key roles in tumorigenesis and therapeutic resistance for a series of Cancer types. Recently small molecular inhibitors have been developed to target USP7. However, the Anticancer mechanism of USP7 inhibitors is still elusive.

Methods: Cell viability or clonogenicity was tested by violet crystal assay. Cell Apoptosis or cell cycle was analyzed by flow cytometry, and chromosome misalignment was observed by a fluorescent microscopy. The protein interaction of PLK1 and USP7 was detected by tandem affinity purification and high throughput proteomics, and further confirmed by co-immunoprecipitation, GST pull-down and protein co-localization. The correlation between USP7 level of tumor tissues and taxane-resistance was evaluated.

Results: Pharmacological USP7 inhibition by P5091 retarded cell proliferation and induced cell Apoptosis. Further studies showed that P5091 induced cell cycle arrest at G2/M phase, and particularly induced chromosome misalignment, indicating the key roles of USP7 in mitosis. USP7 protein was detected in the PLK1-interacted protein complex. USP7 interacts with PLK1 protein through its PBD domain by catalytic activity. USP7 as a Deubiquitinase sustained PLK1 protein stability via the C223 site, and inversely, USP7 inhibition by P5091 promoted the protein degradation of PLK1 through the ubiquitination-proteasome pathway. By overexpressing PLK1, USP7 that had been depleted by RNAi ceased to induce chromosome misalignment in mitosis and again supported cell proliferation and cell survival. Both USP7 and PLK1 were overexpressed in taxane-resistant Cancer cells, and negatively correlated with the MP scores in tumor tissues. Either USP7 or PLK1 knockdown by RNAi significantly sensitized taxane-resistant cells to taxane cell killing.

Conclusion: This is the first report that PLK1 is a novel substrate of USP7 Deubiquitinase, and that USP7 sustained the protein stability of PLK1. USP7 inhibition induces cell Apoptosis and cell cycle G2/M arrest, and overcomes taxane resistance by inducing the protein degradation of PLK1, resulting in chromosome misalignment in mitosis.

Keywords

Apoptosis; Cell cycle arrest; Chromosome misalignment; PLK1; USP7.

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