title: Roles for negative cell regulator 14-3-3sigma in control of MDM2 activities.
abstract: The 14-3-3sigma, upregulated by p53 in response to DNA damage, can have a positive-feedback impact driving p53 activities and is a human cancer epithelial marker downregulated in various tumors. However, the precise roles of 14-3-3sigma during tumorigenesis are not well characterized. Here, we show that 14-3-3sigma is a critical regulator of murine double minute oncogene (MDM2). 14-3-3sigma interacts with MDM2 at the RING domain. The C-terminal region of 14-3-3sigma binds to MDM2 very efficiently. Importantly, 14-3-3sigma overexpression leads to destabilization of MDM2 through enhancing MDM2 self-ubiquitination and accelerating turnover rate. Conversely, loss of 14-3-3sigma results in a significant increase in MDM2 protein. Moreover, live-cell images indicated that 14-3-3sigma can affect the location of MDM2 from the nucleus to the cytoplasm, and that MDM2-mediated cytoplasmic localization of p53 can be reversed by the presence of 14-3-3sigma. Significantly, we further showed that 14-3-3sigma causes MDM2 downregulation, thereby stabilizing p53 and inhibiting tumor growth in animal tumors. Also, 14-3-3sigma blocks MDM2-mediated retinoblastoma degradation and p53 NEDDylation. Our results provide evidence that 14-3-3sigma is a pivotal MDM2 regulator involved in blocking a variety of activities of MDM2.
authors.affiliation: Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: H-Y
authors.initials: HY
authors.lastname: Yang
authors.forename: Y-Y
authors.initials: YY
authors.lastname: Wen
authors.forename: Y-I
authors.initials: YI
authors.lastname: Lin
authors.forename: L
authors.initials: L
authors.lastname: Pham
authors.forename: C-H
authors.initials: CH
authors.lastname: Su
authors.forename: H
authors.initials: H
authors.lastname: Yang
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.forename: M-H
authors.initials: MH
authors.lastname: Lee
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism*; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000075687:NEDD8 Protein; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D054875:Ubiquitination; D014452:Ubiquitins / Q000378:metabolism
chemical_list: D048948:14-3-3 Proteins; D000075687:NEDD8 Protein; C082860:NEDD8 protein, human; D016159:Tumor Suppressor Protein p53; D025801:Ubiquitin; D014452:Ubiquitins; C497206:MDM2 protein, human; C497208:Mdm2 protein, rat; D051736:Proto-Oncogene Proteins c-mdm2; D051057:Proto-Oncogene Proteins c-akt