10 research outputs found

    Role of p53 Serine 46 in p53 Target Gene Regulation

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    The tumor suppressor p53 plays a crucial role in cellular growth control inducing a plethora of different response pathways. The molecular mechanisms that discriminate between the distinct p53-responses have remained largely elusive. Here, we have analyzed the p53-regulated pathways induced by Actinomycin D and Etoposide treatment resulting in more growth arrested versus apoptotic cells respectively. We found that the genome-wide p53 DNA-binding patterns are almost identical upon both treatments notwithstanding transcriptional differences that we observed in global transcriptome analysis. To assess the role of post-translational modifications in target gene choice and activation we investigated the genome-wide level of phosphorylation of Serine 46 of p53 bound to DNA (p53-pS46) and of Serine 15 (p53-pS15). Interestingly, the extent of S46 phosphorylation of p53 bound to DNA is considerably higher in cells directed towards apoptosis while the degree of phosphorylation at S15 remains highly similar. Moreover, our data suggest that following different chemotherapeutical treatments, the amount of chromatin-associated p53 phosphorylated at S46 but not at pS15 is higher on certain apoptosis related target genes. Our data provide evidence that cell fate decisions are not made primarily on the level of general p53 DNA-binding and that post-translationally modified p53 can have distinct DNA-binding characteristics

    The novel p53 target gene IRF2BP2 participates in cell survival during the p53 stress response

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    The tumor suppressor p53 contributes to the cellular fate after genotoxic insults, mainly through the regulation of target genes, thereby allowing e.g. repair mechanisms resulting in cell survival or inducing apoptosis. Unresolved so far is the issue, which exact mechanisms lead to one or the other cellular outcome. Here, we describe the interferon regulatory factor-2-binding protein-2 (IRF2BP2) as a new direct target gene of p53, influencing the p53-mediated cellular decision. We show that upregulation of IRF2BP2 after treatment with actinomycin D (Act.D) is dependent on functional p53 in different cell lines. This occurs in parallel with the down-regulation of the interacting partner of IRF2BP2, the interferon regulatory factor-2 (IRF2), which is known to positively influence cell growth. Analyzing the molecular functions of IRF2BP2, it appears to be able to impede on the p53-mediated transactivation of the p21- and the Bax-gene. We show here that overexpressed IRF2BP2 has an impact on the cellular stress response after Act.D treatment and that it diminishes the induction of apoptosis after doxorubicin treatment. Furthermore, the knockdown of IRF2BP2 leads to an upregulation of p21 and faster induction of apoptosis after doxorubicin as well as Act.D treatment

    Crosstalk between c-Jun and TAp73Ī±/Ī² contributes to the apoptosisā€“survival balance

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    The p53-family member p73 plays a role in various cellular signaling pathways during development and growth control and it can have tumor suppressor properties. Several isoforms of p73 exist with considerable differences in their function. Whereas the functions of the N-terminal isoforms (TA and Ī”Np73) and their opposing pro- and antiapoptotic roles have become evident, the functional differences of the distinct C-terminal splice forms of TAp73 have remained unclear. Here, we characterized the global genomic binding sites for TAp73Ī± and TAp73Ī² by chromatin immunoprecipitation sequencing as well as the transcriptional responses by performing RNA sequencing. We identified a specific p73 consensus binding motif and found a strong enrichment of AP1 motifs in close proximity to binding sites for TAp73Ī±. These AP1 motif-containing target genes are selectively upregulated by TAp73Ī±, while their mRNA expression is repressed upon TAp73Ī² induction. We show that their expression is dependent on endogenous c-Jun and that recruitment of c-Jun to the respective AP1 sites was impaired upon TAp73Ī² expression, in part due to downregulation of c-Jun. Several of these AP1-site containing TAp73Ī±-induced genes impinge on apoptosis induction, suggesting an underlying molecular mechanism for the observed functional differences between TAp73Ī± and TAp73Ī²

    Characterization of genome-wide p53-binding sites upon stress response

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    The tumor suppressor p53 is a sequence-specific transcription factor, which regulates the expression of target genes involved in different stress responses. To understand p53's essential transcriptional functions, unbiased analysis of its DNA-binding repertoire is pivotal. In a genome-wide tiling ChIP-on-chip approach, we have identified and characterized 1546 binding sites of p53 upon Actinomycin D treatment. Among those binding sites were known as well as novel p53 target sites, which included regulatory regions of potentially novel transcripts. Using this collection of genome-wide binding sites, a new high-confidence algorithm was developed, p53scan, to identify the p53 consensus-binding motif. Strikingly, this motif was present in the majority of all bound sequences with 83% of all binding sites containing the motif. In the surrounding sequences of the binding sites, several motifs for potential regulatory cobinders were identified. Finally, we show that the majority of the genome-wide p53 target sites can also be bound by overexpressed p63 and p73 in vivo, suggesting that they can possibly play an important role at p53 binding sites. This emphasizes the possible interplay of p53 and its family members in the context of target gene binding. Our study greatly expands the known, experimentally validated p53 binding site repertoire and serves as a valuable knowledgebase for future research

    Helicobacter pylori Infection Causes Characteristic DNA Damage Patterns in Human Cells

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    Infection with the human pathogen Helicobacter pylori (H.Ā pylori) is a major risk factor for gastric cancer. Since the bacterium exerts multiple genotoxic effects, we examined the circumstances of DNA damage accumulation and identified regions within the host genome with high susceptibility toĀ H.Ā pylori-induced damage. Infection impaired several DNA repair factors, the extent of which depends on a functional cagPAI. This leads to accumulation of a unique DNA damage pattern, preferentially in transcribed regions and proximal to telomeres, in both gastric cell lines and primary gastric epithelial cells. The observed pattern correlates with focal amplifications in adenocarcinomas of the stomach and partly overlaps with known cancer genes. We thus demonstrate an impact of a bacterial infection directed toward specific host genomic regions and describe underlying characteristics that make such regions more likely to acquire heritable changes during infection, which could contribute to cellular transformation

    Knowing me, knowing you : own orientation and information about the

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    The purpose of this study was to examine the effects of motivational orientations on negotiation outcomes in unstable negotiation contexts. Instability was created by pitting individualists against cooperators (mixed dyads), and by giving only one of the parties information about the other partyā€™s orientation. A total of 162 subjects participated in negotiation simulations, where orientation and information were manipulated through instructions from management. The cooperative dyads got better outcomes than did the individualistic dyads. The mixed dyads did as well as the cooperative dyads when the cooperators had information, but did as badly as the individualistic dyads when the individualists had information. The process analyses indicated that the dyads with high outcomes achieved their results because the integrative activities increased over time. In the mixed dyads with informed individualists, the individualists reached higher individual outcome than their cooperative (uninformed) opponents. Thus, naive cooperators can easily be exploited

    The CDK inhibitor CR8 acts as a molecular glue degrader that depletes cyclin K

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    Molecular glue compounds induce protein-protein interactions that, in the context of a ubiquitin ligase, lead to protein degradation; 1; . Unlike traditional enzyme inhibitors, these molecular glue degraders act substoichiometrically to catalyse the rapid depletion of previously inaccessible targets; 2; . They are clinically effective and highly sought-after, but have thus far only been discovered serendipitously. Here, through systematically mining databases for correlations between the cytotoxicity of 4,518 clinical and preclinical small molecules and the expression levels of E3 ligase components across hundreds of human cancer cell lines; 3-5; , we identify CR8-a cyclin-dependent kinase (CDK) inhibitor; 6; -as a compound that acts as a molecular glue degrader. The CDK-bound form of CR8 has a solvent-exposed pyridyl moiety that induces the formation of a complex between CDK12-cyclin K and the CUL4 adaptor protein DDB1, bypassing the requirement for a substrate receptor and presenting cyclin K for ubiquitination and degradation. Our studies demonstrate that chemical alteration of surface-exposed moieties can confer gain-of-function glue properties to an inhibitor, and we propose this as a broader strategy through which target-binding molecules could be converted into molecular glues

    Stack Lee: The man, the music, and the myth

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