title: PU.1 binding to the p53 family of tumor suppressors impairs their transcriptional activity.
abstract: The transcription factor PU.1 is essential for terminal myeloid differentiation, B- and T-cell development, erythropoiesis and hematopoietic stem cell maintenance. PU.1 functions as oncogene in Friend virus-induced erythroleukemia and as tumor suppressor in acute myeloid leukemias. Moreover, Friend virus-induced erythroleukemia requires maintenance of PU.1 expression and the disruption of p53 function greatly accelerates disease progression. It has been hypothesized that p53-mediated expression of the p21(Cip1) cell cycle inhibitor during differentiation of pre-erythroleukemia cells promotes selection against p53 function. In addition to the blockage of erythroblast differentiation provided by increased levels of PU.1, we propose that PU.1 alters p53 function. We demonstrate that PU.1 reduces the transcriptional activity of the p53 tumor suppressor family and thus inhibits activation of genes important for cell cycle regulation and apoptosis. Inhibition is mediated through binding of PU.1 to the DNA-binding and/or oligomerization domains of p53/p73 proteins. Lastly, knocking down endogenous PU.1 in p53 wild-type REH B-cell precursor leukemia cells leads to increased expression of the p53 target p21(Cip1).
authors.affiliation: Experimental Oncology/Hematology, Department of Clinical Research, University of Bern, Bern, Switzerland.
authors.forename: M P
authors.initials: MP
authors.lastname: Tschan
authors.forename: V A
authors.initials: VA
authors.lastname: Reddy
authors.forename: A
authors.initials: A
authors.lastname: Ress
authors.forename: G
authors.initials: G
authors.lastname: Arvidsson
authors.forename: M F
authors.initials: MF
authors.lastname: Fey
authors.forename: B E
authors.initials: BE
authors.lastname: Torbett
mesh_terms: D017209:Apoptosis; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism; D000099232:Proto-Oncogene Protein Spi-1
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D015534:Trans-Activators; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D000099232:Proto-Oncogene Protein Spi-1; C000606460:TP73 protein, human