p53 isoforms
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- MeSH
- finanční podpora výzkumu jako téma MeSH
- imunohistochemie MeSH
- lidé MeSH
- meduloblastom genetika MeSH
- nádorový supresorový protein p53 MeSH
- neuroektodermové nádory genetika MeSH
- pilotní projekty MeSH
- polymerázová řetězová reakce MeSH
- prognóza MeSH
- regulace genové exprese u nádorů genetika imunologie MeSH
- sekvence nukleotidů MeSH
- Check Tag
- lidé MeSH
Cellular senescence is a hallmark of normal aging and aging-related syndromes, including the premature aging disorder Hutchinson-Gilford Progeria Syndrome (HGPS), a rare genetic disorder caused by a single mutation in the LMNA gene that results in the constitutive expression of a truncated splicing mutant of lamin A known as progerin. Progerin accumulation leads to increased cellular stresses including unrepaired DNA damage, activation of the p53 signaling pathway and accelerated senescence. We previously established that the p53 isoforms ∆133p53 and p53β regulate senescence in normal human cells. However, their role in premature aging is unknown. Here we report that p53 isoforms are expressed in primary fibroblasts derived from HGPS patients, are associated with their accelerated senescence and that their manipulation can restore the replication capacity of HGPS fibroblasts. We found that in near-senescent HGPS fibroblasts, which exhibit low levels of ∆133p53 and high levels of p53β, restoration of Δ133p53 expression was sufficient to extend replicative lifespan and delay senescence, despite progerin levels and abnormal nuclear morphology remaining unchanged. Conversely, Δ133p53 depletion or p53β overexpression accelerated the onset of senescence in otherwise proliferative HGPS fibroblasts. Our data indicate that Δ133p53 exerts its role by modulating full-length p53 (FLp53) signaling to extend the replicative lifespan and promotes the repair of spontaneous progerin-induced DNA double-strand breaks (DSBs). We showed that Δ133p53 dominant-negative inhibition of FLp53 occurs directly at the p21/CDKN1A and miR-34a promoters, two p53 senescence-associated genes. In addition, Δ133p53 expression increased the expression of DNA repair RAD51, likely through upregulation of E2F1, a transcription factor that activates RAD51, to promote repair of DSBs. In summary, our data indicate that Δ133p53 modulates p53 signaling to repress progerin-induced early onset of senescence in HGPS cells. Therefore, restoration of ∆133p53 expression may be a novel therapeutic strategy to treat aging-associated phenotypes of HGPS in vivo.
- MeSH
- časové faktory MeSH
- fibroblasty patologie fyziologie MeSH
- kultivované buňky MeSH
- lidé MeSH
- nádorový supresorový protein p53 genetika fyziologie MeSH
- poškození DNA genetika MeSH
- předčasné stárnutí genetika patologie MeSH
- progerie genetika patologie MeSH
- protein - isoformy fyziologie MeSH
- stárnutí buněk genetika MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
The p53 protein is a key tumor suppressor and the most commonly mutated and down-regulated protein in human tumors. It functions mainly through interaction with DNA, and p53 acts as a transcription factor that recognizes the so-called p53 target sites on the promoters of various genes. P53 has been shown to exist as many isoforms, including three C-terminal isoforms that are produced by alternative splicing. Because the C-terminal domain is responsible for sequence-nonspecific binding and regulation of p53 binding, we have analyzed DNA recognition by these C-terminal isoforms. Using atomic force microscopy, we show for the first time that all C-terminal isoforms recognize superhelical DNA. It is particularly noteworthy that a sequence-specific p53 consensus binding site is bound by p53α and β isoforms with similar affinities, whilst p53α shows higher binding to a quadruplex sequence than both p53β and p53γ, and p53γ loses preferential binding to both the consensus binding sequence and the quadruplex-forming sequence. These results show the important role of the variable p53 C-terminal amino acid sequences for DNA recognition.
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 finite proliferative potential of normal human cells leads to replicative cellular senescence, which is a critical barrier to tumour progression in vivo. We show that the human p53 isoforms Delta133p53 and p53beta function in an endogenous regulatory mechanism for p53-mediated replicative senescence. Induced p53beta and diminished Delta133p53 were associated with replicative senescence, but not oncogene-induced senescence, in normal human fibroblasts. The replicatively senescent fibroblasts also expressed increased levels of miR-34a, a p53-induced microRNA, the antisense inhibition of which delayed the onset of replicative senescence. The siRNA (short interfering RNA)-mediated knockdown of endogenous Delta133p53 induced cellular senescence, which was attributed to the regulation of p21(WAF1) and other p53 transcriptional target genes. In overexpression experiments, whereas p53beta cooperated with full-length p53 to accelerate cellular senescence, Delta133p53 repressed miR-34a expression and extended the cellular replicative lifespan, providing a functional connection of this microRNA to the p53 isoform-mediated regulation of senescence. The senescence-associated signature of p53 isoform expression (that is, elevated p53beta and reduced Delta133p53) was observed in vivo in colon adenomas with senescent phenotypes. The increased Delta133p53 and decreased p53beta isoform expression found in colon carcinoma may signal an escape from the senescence barrier during the progression from adenoma to carcinoma.
- MeSH
- genový knockdown MeSH
- lidé MeSH
- mikro RNA metabolismus MeSH
- mutace genetika MeSH
- nádorové buněčné linie MeSH
- nádorový supresorový protein p53 * genetika metabolismus MeSH
- nádory tračníku genetika metabolismus MeSH
- protein - isoformy genetika metabolismus MeSH
- regulace genové exprese u nádorů MeSH
- stárnutí buněk * MeSH
- Check Tag
- lidé MeSH
The p53 family of proteins evolved from a common ancestor into three separate genes encoding proteins that act as transcription factors with distinct cellular roles. Isoforms of each member that lack specific regions or domains are suggested to result from alternative transcription start sites, alternative splicing or alternative translation initiation, and have the potential to exponentially increase the functional repertoire of each gene. However, evidence supporting the presence of individual protein variants at functional levels is often limited and is inferred by mRNA detection using highly sensitive amplification techniques. We provide a critical appraisal of the current evidence for the origins, expression, functions and regulation of p53-family isoforms. We conclude that despite the wealth of publications, several putative isoforms remain poorly established. Future research with improved technical approaches and the generation of isoform-specific protein detection reagents is required to establish the physiological relevance of p53-family isoforms in health and disease. In addition, our analyses suggest that p53-family variants evolved partly through convergent rather than divergent evolution from the ancestral gene.
- MeSH
- alternativní sestřih * MeSH
- lidé MeSH
- messenger RNA metabolismus genetika MeSH
- molekulární evoluce MeSH
- nádorový supresorový protein p53 * metabolismus genetika MeSH
- počátek transkripce MeSH
- protein - isoformy * genetika metabolismus MeSH
- regulace genové exprese MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
The p53 tumor suppressor is a transcription factor with roles in cell development, apoptosis, oncogenesis, aging, and homeostasis in response to stresses and infections. p53 is tightly regulated by the MDM2 E3 ubiquitin ligase. The p53-MDM2 pathway has coevolved, with MDM2 remaining largely conserved, whereas the TP53 gene morphed into various isoforms. Studies on prevertebrate ancestral homologs revealed the transition from an environmentally induced mechanism activating p53 to a tightly regulated system involving cell signaling. The evolution of this mechanism depends on structural changes in the interacting protein motifs. Elephants such as Loxodonta africana constitute ideal models to investigate this coevolution as they are large and long-living as well as having 20 copies of TP53 isoformic sequences expressing a variety of BOX-I MDM2-binding motifs. Collectively, these isoforms would enhance sensitivity to cellular stresses, such as DNA damage, presumably accounting for strong cancer defenses and other adaptations favoring healthy aging. Here we investigate the molecular evolution of the p53-MDM2 system by combining in silico modeling and in vitro assays to explore structural and functional aspects of p53 isoforms retaining the MDM2 interaction, whereas forming distinct pools of cell signaling. The methodology used demonstrates, for the first time that in silico docking simulations can be used to explore functional aspects of elephant p53 isoforms. Our observations elucidate structural and mechanistic aspects of p53 regulation, facilitate understanding of complex cell signaling, and suggest testable hypotheses of p53 evolution referencing Peto's Paradox.
- MeSH
- geny p53 MeSH
- nádorový supresorový protein p53 genetika metabolismus MeSH
- nádory * genetika MeSH
- protein - isoformy genetika metabolismus MeSH
- protoonkogenní proteiny c-mdm2 genetika metabolismus MeSH
- sloni * genetika metabolismus MeSH
- ubikvitinace MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Bidirectional interactions between astrocytes and neurons have physiological roles in the central nervous system and an altered state or dysfunction of such interactions may be associated with neurodegenerative diseases, such as Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS). Astrocytes exert structural, metabolic and functional effects on neurons, which can be either neurotoxic or neuroprotective. Their neurotoxic effect is mediated via the senescence-associated secretory phenotype (SASP) involving pro-inflammatory cytokines (e.g., IL-6), while their neuroprotective effect is attributed to neurotrophic growth factors (e.g., NGF). We here demonstrate that the p53 isoforms Δ133p53 and p53β are expressed in astrocytes and regulate their toxic and protective effects on neurons. Primary human astrocytes undergoing cellular senescence upon serial passaging in vitro showed diminished expression of Δ133p53 and increased p53β, which were attributed to the autophagic degradation and the SRSF3-mediated alternative RNA splicing, respectively. Early-passage astrocytes with Δ133p53 knockdown or p53β overexpression were induced to show SASP and to exert neurotoxicity in co-culture with neurons. Restored expression of Δ133p53 in near-senescent, otherwise neurotoxic astrocytes conferred them with neuroprotective activity through repression of SASP and induction of neurotrophic growth factors. Brain tissues from AD and ALS patients possessed increased numbers of senescent astrocytes and, like senescent astrocytes in vitro, showed decreased Δ133p53 and increased p53β expression, supporting that our in vitro findings recapitulate in vivo pathology of these neurodegenerative diseases. Our finding that Δ133p53 enhances the neuroprotective function of aged and senescent astrocytes suggests that the p53 isoforms and their regulatory mechanisms are potential targets for therapeutic intervention in neurodegenerative diseases.
- MeSH
- alternativní sestřih MeSH
- Alzheimerova nemoc metabolismus patologie MeSH
- amyotrofická laterální skleróza metabolismus patologie MeSH
- astrocyty cytologie účinky léků metabolismus MeSH
- autofagie účinky léků MeSH
- genetické vektory genetika metabolismus MeSH
- interleukin-6 genetika metabolismus MeSH
- kokultivační techniky MeSH
- kultivované buňky MeSH
- leupeptiny farmakologie MeSH
- lidé MeSH
- malá interferující RNA metabolismus MeSH
- mozek metabolismus patologie MeSH
- nádorový supresorový protein p53 antagonisté a inhibitory genetika metabolismus MeSH
- neurony cytologie metabolismus MeSH
- neuroprotekce fyziologie MeSH
- protein - isoformy antagonisté a inhibitory genetika metabolismus MeSH
- RNA interference MeSH
- sekvestosom 1 antagonisté a inhibitory genetika metabolismus MeSH
- serin-arginin sestřihové faktory antagonisté a inhibitory genetika metabolismus MeSH
- stárnutí buněk MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
- Klíčová slova
- proximity ligation assay,
- MeSH
- fluorescenční protilátková technika MeSH
- geny p53 * MeSH
- mapování interakce mezi proteiny * MeSH
- nádorové supresorové proteiny * MeSH
- nádorový supresorový protein p53 MeSH
- nádory patologie MeSH
- oligonukleotidové sondy MeSH
- oligonukleotidy MeSH
- protein - isoformy MeSH
- protilátky MeSH
- Publikační typ
- práce podpořená grantem MeSH
p53 is one of the most studied tumor suppressor proteins that plays an important role in basic biological processes including cell cycle, DNA damage response, apoptosis, and senescence. The human TP53 gene contains alternative promoters that produce N-terminally truncated proteins and can produce several isoforms due to alternative splicing. p53 function is realized by binding to a specific DNA response element (RE), resulting in the transactivation of target genes. Here, we evaluated the influence of quadruplex DNA structure on the transactivation potential of full-length and N-terminal truncated p53α isoforms in a panel of S. cerevisiae luciferase reporter strains. Our results show that a G-quadruplex prone sequence is not sufficient for transcription activation by p53α isoforms, but the presence of this feature in proximity to a p53 RE leads to a significant reduction of transcriptional activity and changes the dynamics between co-expressed p53α isoforms.
- MeSH
- G-kvadruplexy * MeSH
- lidé MeSH
- nádorový supresorový protein p53 genetika metabolismus MeSH
- promotorové oblasti (genetika) genetika MeSH
- protein - isoformy genetika metabolismus MeSH
- proteiny regulující apoptózu genetika metabolismus MeSH
- protoonkogenní proteiny genetika metabolismus MeSH
- responzivní elementy genetika MeSH
- vazba proteinů MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
