Oncogenesis by sequestration of CBP/p300 in transcriptionally inactive hyperacetylated chromatin domains

INSERM, U823, Université Joseph Fourier-Grenoble 1, Institut Albert Bonniot, Grenoble, France.
The EMBO Journal (Impact Factor: 10.43). 09/2010; 29(17):2943-52. DOI: 10.1038/emboj.2010.176
Source: PubMed


In a subset of poorly differentiated and highly aggressive carcinoma, a chromosomal translocation, t(15;19)(q13;p13), results in an in-frame fusion of the double bromodomain protein, BRD4, with a testis-specific protein of unknown function, NUT (nuclear protein in testis). In this study, we show that, after binding to acetylated chromatin through BRD4 bromodomains, the NUT moiety of the fusion protein strongly interacts with and recruits p300, stimulates its catalytic activity, initiating cycles of BRD4-NUT/p300 recruitment and creating transcriptionally inactive hyperacetylated chromatin domains. Using a patient-derived cell line, we show that p300 sequestration into the BRD4-NUT foci is the principal oncogenic mechanism leading to p53 inactivation. Knockdown of BRD4-NUT released p300 and restored p53-dependent regulatory mechanisms leading to cell differentiation and apoptosis. This study demonstrates how the off-context activity of a testis-specific factor could markedly alter vital cellular functions and significantly contribute to malignant cell transformation.

Download full-text


Available from: Daniel Panne
  • Source
    • "Immunofluorescence on TC-797, 797TRex-Flag-BRD4-NUT- HA, and 293TRex-Flag-BRD4-NUT-HA cells was performed as described previously (Reynoird et al. 2010), and nuclei were counterstained with ProLong Gold anti-fade reagent with 4 "
    [Show abstract] [Hide abstract]
    ABSTRACT: NUT midline carcinoma (NMC), a subtype of squamous cell cancer, is one of the most aggressive human solid malignancies known. NMC is driven by the creation of a translocation oncoprotein, BRD4-NUT, which blocks differentiation and drives growth of NMC cells. BRD4-NUT forms distinctive nuclear foci in patient tumors, which we found correlate with ∼100 unprecedented, hyperacetylated expanses of chromatin that reach up to 2 Mb in size. These "megadomains" appear to be the result of aberrant, feed-forward loops of acetylation and binding of acetylated histones that drive transcription of underlying DNA in NMC patient cells and naïve cells induced to express BRD4-NUT. Megadomain locations are typically cell lineage-specific; however, the cMYC and TP63 regions are targeted in all NMCs tested and play functional roles in tumor growth. Megadomains appear to originate from select pre-existing enhancers that progressively broaden but are ultimately delimited by topologically associating domain (TAD) boundaries. Therefore, our findings establish a basis for understanding the powerful role played by large-scale chromatin organization in normal and aberrant lineage-specific gene transcription. © 2015 Alekseyenko et al.; Published by Cold Spring Harbor Laboratory Press.
    Full-text · Article · Jul 2015 · Genes & Development
  • Source
    • "Whether this is related to particular BRD4–NUT translocations remains to be determined, but if so, patients may ultimately need to be stratified for the most appropriate treatment. Interest in the histone deacetylase inhibitor vorinostat as a potential therapy for NMC has arisen through studies linking expression of the BRD4–NUT fusion protein with global changes in chromatin acetylation in NMC cells (Reynoird et al, 2010; Schwartz et al, 2011). Early indications in mouse xenografts demonstrated promising efficacy of this compound in NMC, and in a single patient, vorinostat treatment resulted in dramatic disease regression before adverse toxicity limited its use (Schwartz et al, 2011). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Background: The NUT midline carcinoma (NMC) is a rare but fatal cancer for which systematic testing of therapy options has never been performed. Methods: On the basis of disease biology, we compared the efficacy of the CDK9 inhibitor flavopiridol (FP) with a panel of anticancer agents in NMC cell lines and mouse xenografts. Results: In vitro anthracyclines, topoisomerase inhibitors, and microtubule poisons were among the most cytotoxic drug classes for NMC cells, while efficacy of the bromodomain inhibitor JQ1 varied considerably between lines carrying different BRD4 (bromodomain-containing protein 4)–NUT (nuclear protein in testis) translocations. Efficacy of FP was comparable to vincristine and doxorubicin, drugs that have been previously used in NMC patients. All three compounds showed significantly better activity than etoposide and vorinostat, agents that have also been used in NMC patients. Statins and antimetabolites demonstrated intermediate single-agent efficacy. In vivo, vincristine significantly inhibited tumour growth in two different NMC xenografts. Flavopiridol in vivo was significantly effective in one of the two NMC xenograft lines, demonstrating the biological heterogeneity of this disease. Conclusions: These results demonstrate that FP may be of benefit to a subset of patients with NMC, and warrant a continued emphasis on microtubule inhibitors, anthracyclines, and topoisomerase inhibitors as effective drug classes in this disease.
    Full-text · Article · Feb 2014 · British Journal of Cancer
  • Source
    • "Likewise, expression of NUT (nuclear protein in testis), encoded by a testis specific gene, is abnormally activated through fusion with the ubiquitously expressed BET bromodomain protein-encoding gene, BRD4, in an aggressive subset of carcinoma known as NUT-Midline Carcinoma (French, 2012). The resultant BRD4-NUT fusion gene encodes a fusion protein that behaves as a histone superacetylator, resulting in chromatin hyperacetylation that completely alters the epigenetic landscape of the affected cells (Reynoird et al, 2010). Finally, gene expression profiling in malignant brain tumours derived by inactivation of the l(3)mbt tumour suppressor in Drosophila, has revealed predominant expression of germline specific transcripts some of which were found to be essential for tumour growth (Janic et al, 2010). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Immuno-chemotherapy elicit high response rates in B-cell non-Hodgkin lymphoma but heterogeneity in response duration is observed, with some patients achieving cure and others showing refractory disease or relapse. Using a transcriptome-powered targeted proteomics screen, we discovered a gene regulatory circuit involving the nuclear factor CYCLON which characterizes aggressive disease and resistance to the anti-CD20 monoclonal antibody, Rituximab, in high-risk B-cell lymphoma. CYCLON knockdown was found to inhibit the aggressivity of MYC-overexpressing tumours in mice and to modulate gene expression programs of biological relevance to lymphoma. Furthermore, CYCLON knockdown increased the sensitivity of human lymphoma B cells to Rituximab in vitro and in vivo. Strikingly, this effect could be mimicked by in vitro treatment of lymphoma B cells with a small molecule inhibitor for BET bromodomain proteins (JQ1). In summary, this work has identified CYCLON as a new MYC cooperating factor that autonomously drives aggressive tumour growth and Rituximab resistance in lymphoma. This resistance mechanism is amenable to next-generation epigenetic therapy by BET bromodomain inhibition, thereby providing a new combination therapy rationale for high-risk lymphoma. The nuclear factor CYCLON is a new MYC cooperating factor that drives tumor growth and Rituximab resistance in lymphoma. This resistance mechanism can be targeted by next-generation epigenetic therapy by BET bromodomain inhibition downstream of MYC.
    Full-text · Article · Aug 2013 · EMBO Molecular Medicine
Show more