title: Smad ubiquitylation regulatory factor 1/2 (Smurf1/2) promotes p53 degradation by stabilizing the E3 ligase MDM2.
abstract: The tumor suppressor p53 protein is tightly regulated by a ubiquitin-proteasomal degradation mechanism. Several E3 ubiquitin ligases, including MDM2 (mouse double minute 2), have been reported to play an essential role in the regulation of p53 stability. However, it remains unclear how the activity of these E3 ligases is regulated. Here, we show that the HECT-type E3 ligase Smurf1/2 (Smad ubiquitylation regulatory factor 1/2) promotes p53 degradation by enhancing the activity of the E3 ligase MDM2. We provide evidence that the role of Smurf1/2 on the p53 stability is not dependent on the E3 activity of Smurf1/2 but rather is dependent on the activity of MDM2. We find that Smurf1/2 stabilizes MDM2 by enhancing the heterodimerization of MDM2 with MDMX, during which Smurf1/2 interacts with MDM2 and MDMX. We finally provide evidence that Smurf1/2 regulates apoptosis through p53. To our knowledge, this is the first report to demonstrate that Smurf1/2 functions as a factor to stabilize MDM2 protein rather than as a direct E3 ligase in regulation of p53 degradation.
authors.affiliation: School of Life Sciences, Tsinghua University, Beijing 100842, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Nie
authors.forename: Ping
authors.initials: P
authors.lastname: Xie
authors.forename: Lin
authors.initials: L
authors.lastname: Liu
authors.forename: Guichun
authors.initials: G
authors.lastname: Xing
authors.forename: Zhijie
authors.initials: Z
authors.lastname: Chang
authors.forename: Yuxin
authors.initials: Y
authors.lastname: Yin
authors.forename: Chunyan
authors.initials: C
authors.lastname: Tian
authors.forename: Fuchu
authors.initials: F
authors.lastname: He
authors.forename: Lingqiang
authors.initials: L
authors.lastname: Zhang
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D017209:Apoptosis; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D004795:Enzyme Stability; D006801:Humans; D051379:Mice; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2 / Q000737:chemistry* / Q000378:metabolism*; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D018797:Cell Cycle Proteins; C482775:MDM4 protein, human; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; C498342:SMURF1 protein, human; C471641:SMURF2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D044767:Ubiquitin-Protein Ligases