Casein Kinase 1<i>α</i> Regulates an MDMX Intramolecular Interaction To Stimulate p53 Binding

Wu, Shaofang; Chen, Lihong; Becker, Andreas; Schönbrunn, E.; Chen, Jiandong

doi:10.1128/mcb.00851-12

Cited by 42 publications

(51 citation statements)

References 56 publications

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“…CK1α disrupts this intramolecular interaction, stimulating N-terminal binding to p53. DNA damage inhibits the MDMX-CK1α interaction (13), thus enhancing the MDMX internal binding to conceal the p53-binding pocket.…”

Section: Discussionmentioning

confidence: 99%

“…Our recent study suggested that the MDMX AD regulates the N-terminal domain (13). Inspection of the MDMX sequence identified two central regions with hydrophobic residues that may serve as p53 mimetics (Fig.…”

Section: Detection Of Mdmx Intramolecular Interactions Using Pfr Assaymentioning

confidence: 99%

“…Point mutation analysis showed that W200S/W201G double substitution (referred to as SG) disrupted the p53BD-AD binding in a GST pull-down assay (Fig. 3C) (13). Next, the SG mutation was introduced into MDMXc3 and analyzed by PFR assay.…”

Section: Detection Of Mdmx Intramolecular Interactions Using Pfr Assaymentioning

confidence: 99%

“…CK1α interacts with the central region of MDMX, including the partially disordered acidic region and zinc finger, and promotes phosphorylation of S289 (12). CK1α appears to inhibit a putative intramolecular interaction between the p53 binding domain and central domain of MDMX, suggesting a mechanism by which CK1α stimulates MDMX-p53 binding (13). DNA damage inhibits MDMX-CK1α binding that, in turn, leads to decreased MDMX-p53 binding (13).…”

mentioning

confidence: 99%

“…CK1α appears to inhibit a putative intramolecular interaction between the p53 binding domain and central domain of MDMX, suggesting a mechanism by which CK1α stimulates MDMX-p53 binding (13). DNA damage inhibits MDMX-CK1α binding that, in turn, leads to decreased MDMX-p53 binding (13).…”

mentioning

confidence: 99%

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Autoinhibition of MDMX by intramolecular p53 mimicry

Chen¹,

Borcherds

Wu³

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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The p53 inhibitor MDMX is controlled by multiple stress signaling pathways. Using a proteolytic fragment release (PFR) assay, we detected an intramolecular interaction in MDMX that mechanistically mimics the interaction with p53, resulting in autoinhibition of MDMX. This mimicry is mediated by a hydrophobic peptide located in a long disordered central segment of MDMX that has sequence similarity to the p53 transactivation domain. NMR spectroscopy was used to show this hydrophobic peptide interacts with the N-terminal domain of MDMX in a structurally analogous manner to p53. Mutation of two critical tryptophan residues in the hydrophobic peptide disrupted the intramolecular interaction and increased p53 binding, providing further evidence for mechanistic mimicry. The PFR assay also revealed a second intramolecular interaction between the RING domain and central region that regulates MDMX nuclear import. These results establish the importance of intramolecular interactions in MDMX regulation, and validate a new assay for the study of intramolecular interactions in multidomain proteins with intrinsically disordered regions.T he p53 tumor suppressor is activated by numerous cellular and environmental signals and induces the expression of genes that regulate metabolism, cell growth, cell cycle, apoptosis, and senescence (1). MDM2 and MDMX are key regulators that control the cellular level and transcriptional activity of p53 through direct binding. Mouse knockout experiments showed that both MDM2 and MDMX are essential for controlling p53 activity during embryogenesis. Somatic knockout experiments showed that MDM2 is indispensable for regulating p53 in adult tissues, whereas MDMX deletion does not lead to cell death (2). MDM2 is a well-established p53 transcriptional target that forms a negative feedback loop by binding to the N-terminal transcriptional activation domain of p53 and, subsequently, ubiquitinating the C-terminal regulatory domain, which leads to degradation of p53 by the proteasome. p53 binding sites are also found in intron 1 of human MDMX, and p53 activation leads to moderate induction of MDMX transcription (3). Therefore, MDMX is a p53 target gene that may also provide dynamic feedback in response to p53 activation.MDMX alone does not have E3 ligase activity, but it is important for regulating p53 transcriptional function. MDMX expression and phosphorylation by the ATM/Chk2 pathway is important for the p53-mediated DNA damage response in mice (4, 5). MDMX levels are controlled by MDM2-mediated ubiquitination in a stress-dependent fashion (6, 7). Significant degradation of MDMX occurs after DNA damage through phosphorylation at several C-terminal sites (S342 and S367 by Chk2, S403 by ATM) (8). Furthermore, ribosomal stress promotes MDMX degradation through L11-MDM2 interaction (9), and oncogenic stress promotes MDMX degradation through ARF expression (10). Therefore, key signaling mechanisms that block p53 degradation simultaneously enhance MDMX degradation by MDM2. These observations underscore the co...

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Section: Discussionmentioning

confidence: 99%

Section: Detection Of Mdmx Intramolecular Interactions Using Pfr Assaymentioning

confidence: 99%

Section: Detection Of Mdmx Intramolecular Interactions Using Pfr Assaymentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Autoinhibition of MDMX by intramolecular p53 mimicry

Chen¹,

Borcherds

Wu³

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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RETRACTED: Mutual regulation of MDM4 and TOP2A in cancer cell proliferation

et al. 2019

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MDM 4 and topoisomerase II α ( TOP 2A) are overexpressed in various human cancers. MDM 4 acts as an oncoprotein which promotes cancer progression by inhibiting tumor suppressor p53. As a DNA replication‐ and cell division‐regulating enzyme, TOP 2A is the main target of many anticancer therapy regimens; however, the exact role of TOP 2A in cancer remains elusive. Herein, we report that MDM 4 and TOP 2A bind to each other and are mutually upregulated at the post‐translational level, leading to TOP 2A protein stabilization, inhibition of p53, and increased tumor‐cell proliferation. We demonstrate that the C‐terminal region ( CTR ) of TOP 2A binds to a unique sequence (residues: 188–238) of MDM 4, which contains an auto‐inhibitory segment regulating the MDM 4‐p53 interaction. TOP 2A binding in turn activates MDM 4 for p53 binding, resulting in enhanced inhibition of p53 and cancer cell proliferation. Conversely, binding of the MDM 4 sequence to the CTR of TOP 2A stabilizes TOP 2A protein, leading to increased TOP 2A protein expression. These results reveal novel functions of MDM 4 and TOP 2A as well as their interactions in oncogenesis, suggesting that inhibition of the MDM 4‐ TOP 2A interaction may represent a novel strategy in specifically and simultaneously targeting TOP 2A and MDM 4 for cancer treatment.

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