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Iannetti A, Ledoux AC, Tudhope SJ, Sellier H, Zhao B, Mowla S, Moore A, Hummerich H, Gewurz BE, Cockell SJ, Jat PS, Willmore E, Perkins ND. Regulation of p53 and Rb links the alternative NF-κB pathway to EZH2 expression and cell senescence. PLoS Genet 2014; 10:e1004642. [PMID: 25255445 PMCID: PMC4177746 DOI: 10.1371/journal.pgen.1004642] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 07/28/2014] [Indexed: 11/18/2022] Open
Abstract
There are two major pathways leading to induction of NF-κB subunits. The classical (or canonical) pathway typically leads to the induction of RelA or c-Rel containing complexes, and involves the degradation of IκBα in a manner dependent on IκB kinase (IKK) β and the IKK regulatory subunit NEMO. The alternative (or non-canonical) pathway, involves the inducible processing of p100 to p52, leading to the induction of NF-κB2(p52)/RelB containing complexes, and is dependent on IKKα and NF-κB inducing kinase (NIK). Here we demonstrate that in primary human fibroblasts, the alternative NF-κB pathway subunits NF-κB2 and RelB have multiple, but distinct, effects on the expression of key regulators of the cell cycle, reactive oxygen species (ROS) generation and protein stability. Specifically, following siRNA knockdown, quantitative PCR, western blot analyses and chromatin immunoprecipitation (ChIP) show that NF-κB2 regulates the expression of CDK4 and CDK6, while RelB, through the regulation of genes such as PSMA5 and ANAPC1, regulates the stability of p21WAF1 and the tumour suppressor p53. These combine to regulate the activity of the retinoblastoma protein, Rb, leading to induction of polycomb protein EZH2 expression. Moreover, our ChIP analysis demonstrates that EZH2 is also a direct NF-κB target gene. Microarray analysis revealed that in fibroblasts, EZH2 antagonizes a subset of p53 target genes previously associated with the senescent cell phenotype, including DEK and RacGAP1. We show that this pathway provides the major route of crosstalk between the alternative NF-κB pathway and p53, a consequence of which is to suppress cell senescence. Importantly, we find that activation of NF-κB also induces EZH2 expression in CD40L stimulated cells from Chronic Lymphocytic Leukemia patients. We therefore propose that this pathway provides a mechanism through which microenvironment induced NF-κB can inhibit tumor suppressor function and promote tumorigenesis. Although the classical NF-κB pathway is frequently associated with the induction of cellular senescence and the senescence associated secretory phenotype (SASP), the role of the alternative NF-κB pathway, which is frequently activated in hematological malignancies as well as some solid tumors, has not been defined. We therefore investigated the role of the alternative NF-κB pathway in this process. Here we report that NF-κB2 and RelB, the effectors of the alternative NF-κB pathway, suppress senescence through inhibition of p53 activity. Using primary human fibroblasts, we demonstrate that this is accomplished through NF-κB2/RelB dependent control of a previously unknown pathway, incorporating regulation of CDK4 and 6 expression as well as regulators of p21WAF1 and p53 protein stability. Loss of NF-κB2/RelB results in suppression of retinoblastoma (Rb) tumour suppressor phosphorylation, which in turn leads to inhibition of EZH2 expression and de-repression of p53 activity. Interestingly, we find that CD40 ligand stimulation of cells from Chronic Lymphocytic Leukemia patients, which strongly induces the alternative NF-κB pathway, also induces EZH2 expression. We propose that the alternative NF-κB pathway can promote tumorigenesis through suppression of p53 dependent senescence, a process that may have relevance to cancer cells retaining wild type p53.
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Affiliation(s)
- Alessio Iannetti
- Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, United Kingdom
| | - Adeline C. Ledoux
- Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, United Kingdom
| | - Susan J. Tudhope
- Northern Institute for Cancer Research, Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, United Kingdom
| | - Hélène Sellier
- Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, United Kingdom
| | - Bo Zhao
- Division of Infectious Disease, Brigham and Women's Hospital, Boston, Massachusetts, United States of America
| | - Sophia Mowla
- Department of Neurodegenerative Disease, UCL Institute of Neurology, London, United Kingdom
| | - Adam Moore
- Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, United Kingdom
| | - Holger Hummerich
- Department of Neurodegenerative Disease, UCL Institute of Neurology, London, United Kingdom
| | - Benjamin E. Gewurz
- Division of Infectious Disease, Brigham and Women's Hospital, Boston, Massachusetts, United States of America
| | - Simon J. Cockell
- Bioinformatics Support Unit, Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, United Kingdom
| | - Parmjit S. Jat
- Department of Neurodegenerative Disease, UCL Institute of Neurology, London, United Kingdom
| | - Elaine Willmore
- Northern Institute for Cancer Research, Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, United Kingdom
| | - Neil D. Perkins
- Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, United Kingdom
- * E-mail:
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Abstract
Activation of the NFκB signaling pathway allows the cell to respond to infection and stress and can affect many cellular processes. As a consequence, NFκB activity must be integrated with a wide variety of parallel signaling pathways. One mechanism through which NFκB can exert widespread effects is through controlling the expression of key regulatory kinases. Here we report that NFκB regulates the expression of genes required for centrosome duplication, and that Polo-like kinase 4 (PLK4) is a direct NFκB target gene. RNA interference, chromatin immunoprecipitation, and analysis of the PLK4 promoter in a luciferase reporter assay revealed that all NFκB subunits participate in its regulation. Moreover, we demonstrate that NFκB regulation of PLK4 expression is seen in multiple cell types. Significantly long-term deletion of the NFκB2 (p100/p52) subunit leads to defects in centrosome structure. This data reveals a new component of cell cycle regulation by NFκB and suggests a mechanism through which deregulated NFκB activity in cancer can lead to increased genomic instability and uncontrolled proliferation.
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Affiliation(s)
- Adeline C Ledoux
- Institute for Cell and Molecular Biosciences; Faculty of Medical Sciences; Newcastle University; Newcastle Upon Tyne, UK
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