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Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

p300/CBP transcriptional co-activator proteins play a central role in co-ordinating and integrating multiple signal-dependent events with the transcription apparatus, allowing the appropriate level of gene activity to occur in response to diverse physiological cues that influence, for example, proliferation, differentiation and apoptosis. p300/CBP activity can be under aberrant control in human disease, particularly in cancer, which may inactivate a p300/CBP tumour-suppressor-like activity. The transcription regulating-properties of p300 and CBP appear to be exerted through multiple mechanisms. They act as protein bridges, thereby connecting different sequence-specific transcription factors to the transcription apparatus. Providing a protein scaffold upon which to build a multicomponent transcriptional regulatory complex is likely to be an important feature of p300/CBP control. Another key property is the presence of histone acetyltransferase (HAT) activity, which endows p300/CBP with the capacity to influence chromatin activity by modulating nucleosomal histones. Other proteins, including the p53 tumour suppressor, are targets for acetylation by p300/CBP. With the current intense level of research activity, p300/CBP will continue to be in the limelight and, we can be confident, yield new and important information on fundamental processes involved in transcriptional control.
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PMID:p300/CBP proteins: HATs for transcriptional bridges and scaffolds. 1155 45

The yeast NuA4 complex is a histone H4 and H2A acetyltransferase involved in transcription regulation and essential for cell cycle progression. We identify here a novel subunit of the complex, Yng2p, a plant homeodomain (PHD)-finger protein homologous to human p33/ING1, which has tumor suppressor activity and is essential for p53 function. Mass spectrometry, immunoblotting, and immunoprecipitation experiments confirm the stable stoichiometric association of this protein with purified NuA4. Yeast cells harboring a deletion of the YNG2 gene show severe growth phenotype and have gene-specific transcription defects. NuA4 complex purified from the mutant strain is low in abundance and shows weak histone acetyltransferase activity. We demonstrate conservation of function by the requirement of Yng2p for p53 to function as a transcriptional activator in yeast. Accordingly, p53 interacts with NuA4 in vitro and in vivo, an interaction reminiscent of the p53-ING1 physical link in human cells. The growth defect of Delta yng2 cells can be rescued by the N-terminal part of the protein, lacking the PHD-finger. While Yng2 PHD-finger is not required for p53 interaction, it is necessary for full expression of the p53-responsive gene and other NuA4 target genes. Transcriptional activation by p53 in vivo is associated with targeted NuA4-dependent histone H4 hyperacetylation, while histone H3 acetylation levels remain unchanged. These results emphasize the essential role of the NuA4 complex in the control of cell proliferation through gene-specific transcription regulation. They also suggest that regulation of mammalian cell proliferation by p53-dependent transcriptional activation functions through recruitment of an ING1-containing histone acetyltransferase complex.
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PMID:Role of an ING1 growth regulator in transcriptional activation and targeted histone acetylation by the NuA4 complex. 1160 99

The tumor suppressor protein p53 is a transcription factor that is frequently mutated in human cancers. In response to DNA damage, p53 protein is stabilized and activated by post-translational modifications that enable it to induce either apoptosis or cell cycle arrest. Using a novel yeast p53 dissociator assay, we identify hADA3, a part of histone acetyltransferase complexes, as an important cofactor for p53 activity. p53 and hADA3 physically interact in human cells. This interaction is enhanced dramatically after DNA damage due to phosphorylation event(s) in the p53 N-terminus. Proper hADA3 function is essential for full transcriptional activity of p53 and p53-mediated apoptosis.
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PMID:hADA3 is required for p53 activity. 1170 11

Nuclear factor (NF)-kappaB transcription factors are involved in the control of a large number of normal cellular and organismal processes, such as immune and inflammatory responses, developmental processes, cellular growth, and apoptosis. Transcription of the human immunodeficiency virus type 1 (HIV-1) genome depends on the intracellular environment where the integrate viral DNA is regulated by a complex interplay among viral regulatory proteins, such as Tat, and host cellular transcription factors, such as NF-kappaB, interacting with the viral long terminal repeat region. CBP (CREB-binding protein) and p300, containing an intrinsic histone acetyltransferase (HAT) activity, have emerged as coactivators for various DNA-binding transcription factors. Here, we show that the p50 subunit as well as the p50/p65 of NF-kappaB, and not other factors such as SP1, TFIIB, polymerase II, TFIIA, or p65, can be acetylated by CBP/p300 HAT domain. Acetylation of p50 was completely dependent on the presence of both HAT domain and Tat proteins, implying that Tat influences the transcription machinery by aiding CBP/p300 to acquire new partners and increase its functional repertoire. Three lysines, Lys-431, Lys-440, and Lys-441 in p50 were all acetylated in vitro, and a sequence similarity among p50, p53, Tat, and activin receptor type I on these particular lysines was observed. All proteins have been shown to be acetylated by the CBP/p300 HAT domain. Acetylated p50 increases its DNA binding properties, as evident by streptavidin/biotin pull-down assays when using labeled NF-kappaB oligonucleotides. Increased DNA binding on HIV-1 long terminal repeat coincided with increases in the rate of transcription. Therefore, we propose that acetylation of the DNA binding domain of NF-kappaB aids in nuclear translocation and enhanced transcription and also suggest that the substrate specificity of CBP/p300 can be altered by small peptide molecules, such as HIV-encoded Tat.
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PMID:Enhancement of nuclear factor-kappa B acetylation by coactivator p300 and HIV-1 Tat proteins. 1173 81

Acetylation is a prominent post-translational modification of nucleosomal histone N-terminal tails, which regulates chromatin accessibility. Accordingly, histone acetyltransferases (HATs) play major roles in processes such as transcription. Here, we show that the HAT Tip60, which is involved in DNA repair and apoptosis following gamma irradiation, is subjected to proteasome-dependent proteolysis. Furthermore, we provide evidence that Mdm2, the ubiquitin ligase of the p53 tumour suppressor, interacts physically with Tip60 and induces its ubiquitylation and proteasome-dependent degradation. Moreover, a ubiquitin ligase-defective mutant of Mdm2 had no effect on Tip60 stability. Our results indicate that Mdm2 targets both p53 and Tip60, suggesting that these two proteins could be co-regulated with respect to protein stability. Consistent with this hypothesis, Tip60 levels increased significantly upon UV irradiation of Jurkat cells. Collectively, our results suggest that degradation of Tip60 could be part of the mechanism leading to cell transformation by Mdm2.
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PMID:Tip60 is targeted to proteasome-mediated degradation by Mdm2 and accumulates after UV irradiation. 1192 54

The Epstein-Barr virus nuclear antigen 3C (EBNA3C), encoded by Epstein-Barr virus (EBV), is essential for mediating transformation of human B lymphocytes. Previous studies demonstrated that EBNA3C interacts with a small, nonhistone, highly acidic, high-mobility group-like nuclear protein prothymosin alpha (ProT(alpha)) and the transcriptional coactivator p300 in complexes from EBV-infected cells. These complexes were shown to be associated with histone acetyltransferase (HAT) activity in that they were able to acetylate crude histones in vitro. In this report we show that ProT(alpha) interacts with p300 similarly to p53 and other known oncoproteins at the CH1 amino-terminal domain as well as at a second domain downstream of the bromodomain which includes the CH3 region and HAT domain. Similarly, EBNA3C also interacts with p300 at regions which include the CH1 and CH3/HAT domains, suggesting that ProT(alpha) and EBNAC3C may interact in a complex with p300. We also show that ProT(alpha) activates transcription when targeted to promoters by fusion to the GAL4 DNA binding domain and that this activation is enhanced by the addition of an exogenous source of p300 under the control of a heterologous promoter. This overall activity is down-modulated in the presence of EBNA3C. These results further establish the interaction of cellular coactivator p300 with ProT(alpha) and demonstrate that the associated activities resulting from this interaction, which plays a role in acetylation of histones and coactivation, can be regulated by EBNA3C. Furthermore, this study establishes for the first time a transcriptional role for ProT(alpha) in recruitment or stabilization of coactivator p300, as well as other basal transcription factors, at the nucleosomes for regulation of transcription.
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PMID:Epstein-Barr virus nuclear antigen 3C and prothymosin alpha interact with the p300 transcriptional coactivator at the CH1 and CH3/HAT domains and cooperate in regulation of transcription and histone acetylation. 1196 87

The UV-damaged DNA binding protein complex (UV-DDB) is implicated in global genomic nucleotide excision repair (NER) in mammalian cells. The complex consists of a heterodimer of p127 and p48. UV-DDB is defective in one complementation group (XP-E) of the heritable, skin cancer-prone disorder xeroderma pigmentosum. Upon UV irradiation of primate cells, UV-DDB associates tightly with chromatin, concomitant with the loss of extractable binding activity. We report here that an early event after UV, but not ionizing, radiation is the transient dose-dependent degradation of the small subunit, p48. Treatment of human cells with the proteasomal inhibitor NIP-L3VS blocks this UV-induced degradation of p48. In XP-E cell lines with impaired UV-DDB binding, p48 is resistant to degradation. UV-mediated degradation of p48 occurs independently of the expression of p53 and the cell's proficiency for NER, but recovery of p48 levels at later times (12 h and thereafter) is dependent upon the capacity of the cell to repair non-transcribed DNA. In addition, we find that the p127 subunit of UV-DDB binds in vivo to p300, a histone acetyltransferase. The data support a functional connection between UV-DDB binding activity, proteasomal degradation of p48 and chromatin remodeling during early steps of NER.
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PMID:Sequential binding of UV DNA damage binding factor and degradation of the p48 subunit as early events after UV irradiation. 1203 48

The mammalian ING1 gene encodes a tumor suppressor required for the function of p53. In this study we report a novel function for YNG1, a yeast homolog of ING1. Yng1p is a stable component of the NuA3 histone acetyltransferase complex, which contains Sas3p, the yeast homolog of the mammalian MOZ proto-oncogene product, as its catalytic subunit. Yng1p is required for NuA3 function in vivo but surprisingly is not required for the integrity of the complex. Instead, we find that Yng1p mediates the interaction of Sas3p with nucleosomes and is thus required for the ability of NuA3 to modify histone tails. These data, and the observations that other ING1 homologs are found in additional yeast complexes that posttranslationally modify histones, suggest that members of the ING1 class of proteins may have broad roles in enhancing or modifying the activities of chromatin-modifying complexes, thereby regulating their activities in transcription control.
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PMID:Yng1p modulates the activity of Sas3p as a component of the yeast NuA3 Hhistone acetyltransferase complex. 1207 34

Embryonic stem (ES) cells contain a p53-dependent apoptosis mechanism to avoid the continued proliferation and differentiation of damaged cells. We show that mouse ES cells lacking Ets1 are deficient in their ability to undergo UV-induced apoptosis, similar to p53 null ES cells. In Ets1(-/-) ES cells, UV induction of the p53 regulated genes mdm2, perp, cyclin G and bax was decreased both at mRNA and protein levels. While p53 protein levels were unaltered in Ets1(-/-) cells, its ability to transactivate genes such as mdm2 and cyclin G was reduced. Furthermore, electrophoretic mobility shift assays and immunoprecipitations demonstrated that the presence of Ets1 was necessary for a CBP/p53 complex to be formed. Chromatin immunoprecipitations demonstrated that Ets1 was required for the formation of a stable p53-DNA complex under physiological conditions and activation of histone acetyltransferase activity. These data demonstrate that Ets1 is an essential component of a UV-responsive p53 transcriptional activation complex in ES cells and suggests that Ets1 may contribute to the specificity of p53-dependent gene transactivation in distinct cellular compartments.
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PMID:Ets1 is required for p53 transcriptional activity in UV-induced apoptosis in embryonic stem cells. 1214 8

Gene expression is coordinated in part by interactions between transcriptional activators and other transcription factors such as coactivators. The KIX domain of the coactivator and histone acetyltransferase CREB binding protein (CBP) binds numerous mammalian and viral transcriptional activators such as BRCA1, CREB, c-Jun, c-Myb, p53, papillomavirus E2, and HTLV-1 Tax. Formation of the CREB-CBP complex depends on phosphorylation of the KID region of CREB and involves induced folding of KID upon binding a hydrophobic groove of the KIX domain of CBP. Here we investigate the formation of the complex formed by human KIX and the N-terminal activation domain of human c-Jun. The c-Jun activation domain and KID do not share significant sequence similarity. Circular dichroism spectroscopy shows that the Jun N-terminal activation domain is intrinsically disordered in isolation and that KIX binding is independent of Jun phosphorylation. In contrast to the mode of binding exhibited by CREB, NMR chemical shift mapping indicates that the c-Jun activation domain binds to a distinctly different surface of KIX than used by CREB. Moreover, NMR and sedimentation equilibrium studies show that the activation domains of c-Jun and CREB can simultaneously bind the KIX domain of CBP. The results illustrate a new mode of binding and combinatorial recruitment via the KIX domain of CBP by multiple transcriptional activators.
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PMID:Structurally distinct modes of recognition of the KIX domain of CBP by Jun and CREB. 1243 52


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