title: Plk1-mediated phosphorylation of Topors regulates p53 stability.
abstract: Polo-like kinase 1 (Plk1) overexpression is associated with tumorigenesis by an unknown mechanism. Likewise, Plk1 was suggested to act as a negative regulator of tumor suppressor p53, but the mechanism remains to be determined. Herein, we have identified topoisomerase I-binding protein (Topors), a p53-binding protein, as a Plk1 target. We show that Plk1 phosphorylates Topors on Ser(718) in vivo. Significantly, expression of a Plk1-unphosphorylatable Topors mutant (S718A) leads to a dramatic accumulation of p53 through inhibition of p53 degradation. Topors is an ubiquitin and small ubiquitin-like modifier ubiquitin-protein isopeptide ligase (SUMO E3) ligase. Plk1-mediated phosphorylation of Topors inhibits Topors-mediated sumoylation of p53, whereas p53 ubiquitination is enhanced, leading to p53 degradation. These results demonstrate that Plk1 modulates Topors activity in suppressing p53 function and identify a likely mechanism for the tumorigenic potential of Plk1.
authors.affiliation: College of Chemistry, Sichuan University, Chengdu 610064, China.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Yang
authors.forename: Hongchang
authors.initials: H
authors.lastname: Li
authors.forename: Zinan
authors.initials: Z
authors.lastname: Zhou
authors.forename: Wen-Horng
authors.initials: WH
authors.lastname: Wang
authors.forename: Anping
authors.initials: A
authors.lastname: Deng
authors.forename: Ourania
authors.initials: O
authors.lastname: Andrisani
authors.forename: Xiaoqi
authors.initials: X
authors.lastname: Liu
mesh_terms: D018797:Cell Cycle Proteins / Q000378:metabolism*; D002460:Cell Line; D045744:Cell Line, Tumor; D005786:Gene Expression Regulation; D016158:Genes, p53; D006801:Humans; D008954:Models, Biological; D009154:Mutation; D009363:Neoplasm Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D000097869:Polo-Like Kinase 1
chemical_list: D018797:Cell Cycle Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; D044767:Ubiquitin-Protein Ligases; D000097869:Polo-Like Kinase 1; C495901:TP53 protein, human; C120157:TOPORS protein, human