Association of p19ARF with Mdm2 inhibits ubiquitin ligase activity of Mdm2 for tumor suppressor p53

BRCA1 C-terminal (BRCT) domains in BRCA1 are essential for tumor suppressor function, though the underlying mechanisms remain unclear. We identified ezrin, radixin, and moesin as BRCA1 BRCT domain–interacting proteins. Ezrin–radixin–moesin (ERM) and F-actin colocalized with BRCA1 at the plasma membrane (PM) of cancer cells, especially at leading edges and focal adhesion sites. In stably expressing cancer cells, high levels of enhanced green fluorescent protein (EGFP)-BRCA11634–1863 acted as a dominant-negative factor, displacing endogenous BRCA1 from the PM. This led to delayed cell spreading, increased spontaneous motility, and irregular monolayer wound healing. MCF-7 cells (intact BRCA1) showed lower motility than HCC1937 cells (truncated BRCA1), but expression of EGFP-BRCA11634–1863 in MCF-7 increased motility. Conversely, full-length BRCA1 expression in HCC1937 decreased motility but only if the protein retained ubiquitin ligase activity. We conclude that full-length BRCA1 is important for complete tumor suppressor activity via interaction of its BRCT domains with ERM at the PM, controlling spreading and motility of cancer cells via ubiquitin ligase activity.

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Diverse Effects of Mutations in Exon II of the von Hippel-Lindau (VHL) Tumor Suppressor Gene on the Interaction of pVHL with the Cytosolic Chaperonin and pVHL-Dependent Ubiquitin Ligase Activity

Molecular and Cellular Biology ◽

10.1128/mcb.22.6.1947-1960.2002 ◽

2002 ◽

Vol 22 (6) ◽

pp. 1947-1960 ◽

Cited By ~ 52

Author(s):

William J. Hansen ◽

Michael Ohh ◽

Javid Moslehi ◽

Keiichi Kondo ◽

William G. Kaelin ◽

...

Keyword(s):

Tumor Suppressor ◽

Ubiquitin Ligase ◽

Hypoxia Inducible Factor ◽

Detectable Effect ◽

Missense Mutations ◽

Subsequent Formation ◽

Von Hippel Lindau ◽

Ubiquitin Ligase Activity

ABSTRACT We examined the biogenesis of the von Hippel-Lindau (VHL) tumor suppressor protein (pVHL) in vitro and in vivo. pVHL formed a complex with the cytosolic chaperonin containing TCP-1 (CCT or TRiC) en route to assembly with elongin B/C and the subsequent formation of the VCB-Cul2 ubiquitin ligase. Blocking the interaction of pVHL with elongin B/C resulted in accumulation of pVHL within the CCT complex. pVHL present in purified VHL-CCT complexes, when added to rabbit reticulocyte lysate, proceeded to form VCB and VCB-Cul2. Thus, CCT likely functions, at least in part, by retaining VHL chains pending the availability of elongin B/C for final folding and/or assembly. Tumor-associated mutations within exon II of the VHL syndrome had diverse effects upon the stability and/or function of pVHL-containing complexes. First, a pVHL mutant lacking the entire region encoded by exon II did not bind to CCT and yet could still assemble into complexes with elongin B/C and elongin B/C-Cul2. Second, a number of tumor-derived missense mutations in exon II did not decrease CCT binding, and most had no detectable effect upon VCB-Cul2 assembly. Many exon II mutants, however, were found to be defective in the binding to and subsequent ubiquitination of hypoxia-inducible factor 1α (HIF-1α), a substrate of the VCB-Cul2 ubiquitin ligase. We conclude that the selection pressure to mutate VHL exon II during tumorigenesis does not relate to loss of CCT binding but may reflect quantitative or qualitative defects in HIF binding and/or in pVHL-dependent ubiquitin ligase activity.

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The Ubiquitin Ligase COP1 Promotes Glioma Cell Proliferation by Preferentially Downregulating Tumor Suppressor p53

Molecular Neurobiology ◽

10.1007/s12035-016-0033-x ◽

2016 ◽

Vol 54 (7) ◽

pp. 5008-5016 ◽

Cited By ~ 12

Author(s):

Shenshan Zou ◽

Yufu Zhu ◽

Bin Wang ◽

Fengyuan Qian ◽

Xiang Zhang ◽

...

Keyword(s):

Cell Proliferation ◽

Tumor Suppressor ◽

Ubiquitin Ligase ◽

Glioma Cell ◽

Tumor Suppressor P53 ◽

Glioma Cell Proliferation

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Imaging and kinetics of the bimolecular complex formed by the tumor suppressor p53 with ubiquitin ligase COP1 as studied by atomic force microscopy and surface plasmon resonance

International Journal of Nanomedicine ◽

10.2147/ijn.s152214 ◽

2018 ◽

Vol Volume 13 ◽

pp. 251-259 ◽

Cited By ~ 9

Author(s):

Ilaria Moscetti ◽

Anna Rita Bizzarri ◽

Salvatore Cannistraro

Keyword(s):

Atomic Force Microscopy ◽

Surface Plasmon Resonance ◽

Tumor Suppressor ◽

Surface Plasmon ◽

Ubiquitin Ligase ◽

Plasmon Resonance ◽

Tumor Suppressor P53 ◽

Force Microscopy ◽

Atomic Force ◽

Kinetics Of

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Competitive ubiquitination activates the tumor suppressor p53

Cell Death and Differentiation ◽

10.1038/s41418-019-0463-x ◽

2019 ◽

Vol 27 (6) ◽

pp. 1807-1818 ◽

Cited By ~ 2

Author(s):

Xingyao Li ◽

Mengqi Guo ◽

Lun Cai ◽

Tingting Du ◽

Ying Liu ◽

...

Keyword(s):

Transcription Factor ◽

Catalytic Activity ◽

Tumor Suppressor ◽

Ubiquitin Ligase ◽

E3 Ubiquitin Ligase ◽

Activating Transcription Factor 3 ◽

Tumor Suppressor P53 ◽

Unknown Mechanism ◽

P53 Activation ◽

Activating Transcription Factor

AbstractBlocking p53 ubiquitination through disrupting its interaction with MDM2 or inhibiting the MDM2 catalytic activity is the central mechanism by which the tumor suppressor p53 is activated in response to genotoxic challenges. Although MDM2 is first characterized as the major E3 ubiquitin ligase for p53, it can also catalyze the conjugation of ubiquitin moieties to other proteins (e.g., activating transcription factor 3, or ATF3). Here we report that ATF3 can act as an ubiquitin “trap” and competes with p53 for MDM2-mediated ubiquitination. While ATF3-mediated p53 stabilization required ATF3 binding to the MDM2 RING domain, we demonstrated that ATF3 ubiquitination catalyzed by MDM2 was indispensable for p53 activation in response to DNA damage. Moreover, a cancer-derived ATF3 mutant (R88G) devoid of ubiquitination failed to prevent p53 from MDM2-mediated degradation and thus was unable to activate the tumor suppressor. Therefore, we have identified a previously-unknown mechanism that can activate p53 in the genotoxic response.

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