title: Direct binding of apoptosis signal-regulating kinase 1 to retinoblastoma protein: novel links between apoptotic signaling and cell cycle machinery.
abstract: The retinoblastoma protein Rb has antiproliferative and antiapoptotic functions. Our previous studies have shown that certain apoptotic signals can inactivate Rb via the p38 pathway. Here we show that Rb associates with the apoptosis signal-regulating kinase ASK1 in response to specific apoptotic signals. An LXCXE motif on ASK1 was required for Rb binding; this correlated with increased E2F1 transcriptional activity and up-regulation of the proapoptotic protein p73. Overexpression of Rb inhibited ASK1-induced apoptosis; in addition, an ASK1 mutant incapable of binding Rb could not induce apoptosis, indicating that ASK1 has to overcome the antiapoptotic properties of Rb to kill cells. Chromatin immunoprecipitation assays show that in asynchronous cells the p73P1 promoter is occupied predominantly by E2F3; upon tumor necrosis factor (TNF)-alpha stimulation, E2F3 is dissociated from the promoter and replaced by E2F1. At the same time, TNF-alpha stimulation causes Rb to dissociate from the p73P1 promoter. These are promoter-specific events because Rb binds to the mitogenic cdc25A promoter upon TNF-alpha stimulation. These studies suggest that Rb acts as a link between apoptotic and proliferative pathways by interacting with distinct kinases and occupying different promoters.
authors.affiliation: Department of Interdisciplinary Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, USA.
authors.forename: Piyali
authors.initials: P
authors.lastname: Dasgupta
authors.forename: Vicki
authors.initials: V
authors.lastname: Betts
authors.forename: Shipra
authors.initials: S
authors.lastname: Rastogi
authors.forename: Bharat
authors.initials: B
authors.lastname: Joshi
authors.forename: Mark
authors.initials: M
authors.lastname: Morris
authors.forename: Brenda
authors.initials: B
authors.lastname: Brennan
authors.forename: Dalia
authors.initials: D
authors.lastname: Ordonez-Ercan
authors.forename: Srikumar
authors.initials: S
authors.lastname: Chellappan
mesh_terms: D020816:Amino Acid Motifs; D017209:Apoptosis; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division; D002460:Cell Line; D002843:Chromatin / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D050699:E2F3 Transcription Factor; D019084:Fluorescent Antibody Technique, Indirect; D016147:Genes, Tumor Suppressor; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D048848:MAP Kinase Kinase Kinase 5; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016160:Retinoblastoma Protein / Q000378:metabolism*; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D050699:E2F3 Transcription Factor; C098319:E2F3 protein, human; D009687:Nuclear Proteins; D016160:Retinoblastoma Protein; C000606460:TP73 protein, human; D014157:Transcription Factors; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins; D005982:Glutathione Transferase; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048848:MAP Kinase Kinase Kinase 5; D020930:MAP Kinase Kinase Kinases; C482858:MAP3K5 protein, human