Cellular stress conditions activate p53-dependent pathways to counteract the inflicted damage. To achieve the required functional diversity, p53 is subjected to numerous post-translational modifications and the expression of isoforms. Little is yet known how p53 has evolved to respond to different stress pathways. The p53 isoform p53/47 (p47 or ΔNp53) is linked to aging and neural degeneration and is expressed in human cells via an alternative cap-independent translation initiation from the 2nd in-frame AUG at codon 40 (+118) during endoplasmic reticulum (ER) stress. Despite an AUG codon in the same location, the mouse p53 mRNA does not express the corresponding isoform in either human or mouse-derived cells. High-throughput in-cell RNA structure probing shows that p47 expression is attributed to PERK kinase-dependent structural alterations in the human p53 mRNA, independently of eIF2α. These structural changes do not take place in murine p53 mRNA. Surprisingly, PERK response elements required for the p47 expression are located downstream of the 2nd AUG. The data show that the human p53 mRNA has evolved to respond to PERK-mediated regulation of mRNA structures in order to control p47 expression. The findings highlight how p53 mRNA co-evolved with the function of the encoded protein to specify p53-activities under different cellular conditions.

• MeSH
• kinasa eIF-2 genetika   metabolismus   MeSH
• lidé MeSH
• messenger RNA genetika   metabolismus   MeSH
• myši MeSH
• nádorový supresorový protein p53 * genetika   metabolismus   MeSH
• posttranslační úpravy proteinů MeSH
• protein - isoformy metabolismus   MeSH
• stres endoplazmatického retikula * genetika   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The p53 tumor suppressor and its key regulator MDM2 play essential roles in development, ageing, cancer, and cellular stress responses in mammals. Following DNA damage, MDM2 interacts with p53 mRNA in an ATM kinase-dependent fashion and stimulates p53 synthesis, whereas under normal conditions, MDM2 targets the p53 protein for degradation. The peptide- and RNA motifs that interact with MDM2 are encoded by the same conserved BOX-I sequence, but how these interactions have evolved is unknown. Here, we show that a temperature-sensitive structure in the invertebrate Ciona intestinalis (Ci) p53 mRNA controls its interaction with MDM2. We also show that a nonconserved flanking region of Ci-BOX-I domain prevents the p53-MDM2 protein-protein interaction. These results indicate that the temperature-regulated p53 mRNA-MDM2 interaction evolved to become kinase regulated in the mammalian DNA damage response. The data also suggest that the negative regulation of p53 by MDM2 via protein-protein interaction evolved in vertebrates following changes in the BOX-I flanking sequence.

• MeSH
• apoptóza genetika   MeSH
• Ciona intestinalis MeSH
• DNA primery MeSH
• messenger RNA genetika   metabolismus   MeSH
• nádorové buněčné linie MeSH
• nádorový supresorový protein p53 genetika   metabolismus   MeSH
• poškození DNA MeSH
• protoonkogenní proteiny c-mdm2 genetika   metabolismus   MeSH
• RRM proteiny genetika   metabolismus   MeSH
• sekvence nukleotidů MeSH
• terciární struktura proteinů MeSH
• vazba proteinů MeSH
• vztahy mezi strukturou a aktivitou MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Regulated protein synthesis via changes in mRNA structures forms an important part of how prokaryotic cells adapt protein expression in response to changes in the environment. Little is known regarding how this concept has adapted to regulate mRNA translation via signaling pathways in mammalian cells. Here, we show that following phosphorylation by the ataxia telangiectasia mutated (ATM) kinase at serine 403, the C-terminal RING domain of HDMX binds the nascent p53 mRNA to promote a conformation that supports the p53 mRNA-HDM2 interaction and the induction of p53 synthesis. HDMX and its homolog HDM2 bind the same p53 internal ribosome entry sequences (IRES) structure but with different specificity and function. The results show how HDMX and HDM2 act as nonredundant IRES trans-acting factors (ITAFs) to bring a positive synergistic effect on p53 expression during genotoxic stress by first altering the structure of the newly synthesized p53 mRNA followed by stimulation of translation.

• MeSH
• ATM protein metabolismus   MeSH
• fosforylace MeSH
• jaderné proteiny chemie   fyziologie   MeSH
• lidé MeSH
• messenger RNA chemie   genetika   metabolismus   MeSH
• molekulární sekvence - údaje MeSH
• nádorový supresorový protein p53 genetika   metabolismus   MeSH
• obrácené repetice MeSH
• poškození DNA MeSH
• posttranskripční úpravy RNA MeSH
• posttranslační úpravy proteinů MeSH
• proteosyntéza MeSH
• protoonkogenní proteiny c-mdm2 metabolismus   MeSH
• protoonkogenní proteiny chemie   fyziologie   MeSH
• regulace genové exprese MeSH
• sbalování RNA MeSH
• sekvence nukleotidů MeSH
• Sf9 buňky MeSH
• Spodoptera MeSH
• substrátová specifita MeSH
• terciární struktura proteinů MeSH
• vazba proteinů MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Regulace exprese proteinu p53 je kritická pro kontrolu jeho aktivity v normálních i poškozených buňkách. Velmi dobře je popsána úloha E3 ubikvitin ligázy MDM2, která je za normálních podmínek zodpovědná za degradaci p53 v proteazomu a je esenciální při kontrole aktivity p53 během vývoje organizmu. Nadměrná exprese MDM2 spolu s některými dalšími E3 ligázami podílejícími se rovněž na regulaci stability p53 byla prokázána u řady lidských nádorů, což jen podtrhuje význam posttranslační regulace hladiny proteinu p53. Za stresových podmínek se hladina TP53 na úrovni mRNA zásadně nemění, naopak vše nasvědčuje tomu, že syntéza proteinu p53 je řízena především na úrovni iniciace translace, což představuje významný mechanizmus zodpovědný za kontrolu exprese p53. Na druhou stranu současné práce ukazují, že i TP53 mRNA hraje důležitou roli při regulaci aktivity proteinu p53 v buňce. Proto jsme se v této práci zaměřili a diskutujeme mechanizmy zodpovědné za kontrolu syntézy proteinu p53 a jejich úlohu při regulaci p53 aktivity za normálních podmínek a při různých typech stresu.

The regulation of p53 expression levels is critical in controlling p53 activity in normal and dama­ged cells. This is well illustrated by the E3 ubiquitin ligase MDM2 that targets p53 for proteasomal degradation under normal conditions and is essential for controlling p53 acti­vity during development. MDM2 is over-expressed in human cancers and together with some other E3 ligases that have also been implicated in controlling p53 stability, which emphasises the importance of post-translational regulation of p53 expression. At the level of synthesis, TP53 mRNA levels do not change in response to stresses and it is instead its rate of translation initiation that provides the mechanism of choice for expression control. More recent work has shown that TP53 mRNA plays an important role in mediating the cellular regulation of p53 activity. We will discuss the regulation of p53 synthesis and its implications for controlling p53 activity under normal conditions and during different types of stress response.

• Klíčová slova
• syntéza p53, RNA-vazebné proteiny, odpověď na stres,
• MeSH
• fyziologický stres MeSH
• IRES MeSH
• lidé MeSH
• messenger RNA MeSH
• nádorový supresorový protein p53 * fyziologie   MeSH
• nádory genetika   patofyziologie   MeSH
• oxidační stres MeSH
• poškození DNA MeSH
• protein - isoformy MeSH
• proteosyntéza * MeSH
• protoonkogenní proteiny c-mdm2 MeSH
• protoonkogenní proteiny * genetika   metabolismus   MeSH
• regulace genové exprese u nádorů MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• práce podpořená grantem MeSH

The function and regulation of MDM2 as a component of a p53-dependent negative feedback loop has formed a core paradigm in the p53 field. This concept, now 20 years old, has been solidified by fields of protein science, transgenic technology, and drug discovery in human cancer. However, it has been noted that a simple negative feedback loop between p53 and MDM2 lacks an intrinsic "activating" step that counteracts this inhibition and permits oscillation of the feedback to occur as p53 is switched on and off. More recent work has identified a solution to the missing piece of the picture that counters the negative feedback loop, which is MDM2 itself. Under conditions of genotoxic stress, MDM2 helps to activate p53 by increasing its rate of protein synthesis. This simple observation makes certain aspects of the p53 response more comprehensible such as why MDM2 is upregulated by p53 early on following DNA damage and how phosphorylation of MDM2 at the C-terminal Ser395 by ATM translates into p53 activation. The latter acts by inducing allosteric changes in the RING domain of MDM2 that expose its RNA binding pocket, support p53 synthesis, and suppress its degradation. This allosteric nature of MDM2 in the C-terminus mirrors the allosteric effects of the binding of small molecules to the p53 interacting pocket at the N-terminus of MDM2, which opens the core domain of MDM2 to central domains of p53, which controls p53 ubiquitination. Thus, the highly allosteric nature of MDM2 provides the basis for dynamic protein-protein interactions and protein-RNA interactions through which MDM2's activity is regulated in p53 protein destruction or in p53 protein synthesis. We discuss these mechanisms and how this information can be exploited for drug development programs aimed at activating p53 via targeting MDM2.

• Publikační typ
• časopisecké články MeSH