Linzen, U.* ; Lilischkis, R.* ; Pandithage, R.* ; Schilling, B.* ; Ullius, A.* ; Luscher-Firzlaff, J.* ; Kremmer, E. ; Lüscher, B.* ; Vervoorts, J.*
     
    
        
ING5 is phosphorylated by CDK2 and controls cell proliferation independently of p53.
    
    
        
    
    
        
        PLoS ONE 10:e0123736 (2015)
    
    
    
      
      
	
	    Inhibitor of growth (ING) proteins have multiple functions in the control of cell proliferation, mainly by regulating processes associated with chromatin regulation and gene expression. ING5 has been described to regulate aspects of gene transcription and replication. Moreover deregulation of ING5 is observed in different tumors, potentially functioning as a tumor suppressor. Gene transcription in late G1 and in S phase and replication is regulated by cyclin-dependent kinase 2 (CDK2) in complex with cyclin E or cyclin A. CDK2 complexes phosphorylate and regulate several substrate proteins relevant for overcoming the restriction point and promoting S phase. We have identified ING5 as a novel CDK2 substrate. ING5 is phosphorylated at a single site, threonine 152, by cyclin E/CDK2 and cyclin A/CDK2 in vitro. This site is also phosphorylated in cells in a cell cycle dependent manner, consistent with it being a CDK2 substrate. Furthermore overexpression of cyclin E/CDK2 stimulates while the CDK2 inhibitor p27KIP1 represses phosphorylation at threonine 152. This site is located in a bipartite nuclear localization sequence but its phosphorylation was not sufficient to deregulate the subcellular localization of ING5. Although ING5 interacts with the tumor suppressor p53, we could not establish p53-dependent regulation of cell proliferation by ING5 and by phospho-site mutants. Instead we observed that the knockdown of ING5 resulted in a strong reduction of proliferation in different tumor cell lines, irrespective of the p53 status. This inhibition of proliferation was at least in part due to the induction of apoptosis. In summary we identified a phosphorylation site at threonine 152 of ING5 that is cell cycle regulated and we observed that ING5 is necessary for tumor cell proliferation, without any apparent dependency on the tumor suppressor p53.
	
	
	    
	
       
      
	
	    
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        Publication type
        Article: Journal article
    
 
    
        Document type
        Scientific Article
    
 
    
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        Keywords
        Cyclin-dependent Kinases; Dna-replication; A1-cdk2 Complex; Somatic-cells; Cancer Cells; Gene Family; Expression; Acetylation; Transcription; Protein
    
 
    
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        Language
        english
    
 
    
        Publication Year
        2015
    
 
    
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        HGF-reported in Year
        2015
    
 
    
    
        ISSN (print) / ISBN
        1932-6203
    
 
    
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	    Volume: 10,  
	    Issue: 4,  
	    Pages: ,  
	    Article Number: e0123736 
	    Supplement: ,  
	
    
 
    
        
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            Publisher
            Public Library of Science (PLoS)
        
 
        
            Publishing Place
            Lawrence, Kan.
        
 
	
        
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        Reviewing status
        Peer reviewed
    
 
     
    
        POF-Topic(s)
        30504 - Mechanisms of Genetic and Environmental Influences on Health and Disease
    
 
    
        Research field(s)
        Immune Response and Infection
    
 
    
        PSP Element(s)
        G-501793-001
    
 
    
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        Erfassungsdatum
        2015-04-12