Role of the E1A Rb-binding domain in repression of the NF-kappa B-dependent defense against tumor necrosis factor-alpha.
The adenoviral E1A oncogene sensitizes mammalian cells to tumor necrosis factor-alpha (TNF-alpha), in part by repressing the nuclear factor-kappa B (NF-kappa B)-dependent defense against this cytokine. Other E1A activities involve binding to either p300/cyclic AMP response element-binding protein (CBP) or retinoblastoma (Rb)-family proteins, but the roles of E1A interactions with these transcriptional regulators in sensitizing cells to TNF-alpha are unclear. E1A expression did not block upstream events in TNF-alpha-induced activation of NF-kappa B in NIH 3T3 cells, including degradation of I kappa B-alpha, nuclear translocation of NF-kappa B subunits, and their dimeric binding to kappa B sequences in the nucleus. However, E1A markedly repressed NF-kappa B-dependent transcription and sensitized cells to TNF-alpha induced apoptosis. These E1A effects were selective for kappa B-dependent transcription and for the function of the NF-kappa B p65/RelA subunit. A four amino acid E1A deletion that eliminates binding to Rb-family proteins blocked both repression of TNF-alpha-induced transcription and sensitization to apoptosis. In contrast, mutations that eliminate E1A binding to p300/CBP (coactivators of p65/RelA) did not affect either E1A activity. These data suggest that E1A-Rb-binding blocks the NF-kappa B-dependent activation response to TNF-alpha by altering the function of p65/RelA at a stage after formation of the transcription factor-enhancer complex. These observations also open questions about the general role of Rb-family proteins in modulation of NF-kappa B-dependent transcription.
Department of Medicine and the Cancer Center, University of Illinois College of Medicine, MC-735, Chicago, IL 60612, USA. JLCook@uic.edu
James L
JL
Cook
Thomas A
TA
Walker
G Scott
GS
Worthen
Jay R
JR
Radke
D016475:3T3 Cells; D017500:Adenovirus E1A Proteins / Q000235:genetics / Q000494:pharmacology*; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001665:Binding Sites; D017124:Conserved Sequence; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D019281:Dimerization; D005091:Exons; D005786:Gene Expression Regulation; D006801:Humans; D020672:I-kappa B Proteins; D051379:Mice; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D011994:Recombinant Proteins / Q000276:immunology / Q000494:pharmacology; D016160:Retinoblastoma Protein / Q000276:immunology*; D014158:Transcription, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics* / Q000494:pharmacology*
D017500:Adenovirus E1A Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D011994:Recombinant Proteins; D016160:Retinoblastoma Protein; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha