title: PU.1, interferon regulatory factor (IRF) 2, and the interferon consensus sequence-binding protein (ICSBP/IRF8) cooperate to activate NF1 transcription in differentiating myeloid cells.
abstract: Nf1 (neurofibromin 1) is a Ras-GAP protein that regulates cytokine-induced proliferation of myeloid cells. In previous studies, we found that the interferon consensus sequence-binding protein (ICSBP; also referred to as interferon regulatory factor 8) activates transcription of the gene encoding Nf1 (the NF1 gene) in differentiating myeloid cells. We also found that NF1 activation requires cytokine-stimulated phosphorylation of a conserved tyrosine residue in the interferon regulatory factor (IRF) domain of ICSBP/IRF8. In this study, we found that ICSBP/IRF8 cooperates with PU.1 and interferon regulatory factor 2 to activate a composite ets/IRF-cis element in the NF1 promoter. We found that PU.1 binds directly to the NF1-cis element, and DNA-bound PU.1 interacts with IRF2, recruiting IRF2 to the cis element. This interaction requires cytokine-induced phosphorylation of specific serine residues in the PU.1 PEST domain and of a conserved tyrosine residue in the IRF domain of IRF2. We found that ICSBP/IRF8 interaction with the NF1-cis element requires pre-binding of PU.1 and IRF2. The conserved IRF domain tyrosine in ICSBP/IRF8 is required for interaction with the DNA-bound PU.1-IRF2 heterodimer. NF1 deficiency in myeloid progenitor cells results in cytokine hypersensitivity and myeloproliferation. Therefore, these studies identify a target gene for the previously observed tumor-suppressor effect of PU.1. Additionally, these studies identify a tumor-suppressor function for the "oncogenic" transcription factor, IRF2.
authors.affiliation: The Feinberg School of Medicine and The Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, Illinois 60611, USA.
authors.forename: Weiqi
authors.initials: W
authors.lastname: Huang
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Horvath
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Eklund
mesh_terms: D002454:Cell Differentiation; D002460:Cell Line; D019281:Dimerization; D006801:Humans; D050836:Interferon Regulatory Factor-2 / Q000378:metabolism / Q000502:physiology*; D050835:Interferon Regulatory Factors / Q000378:metabolism / Q000502:physiology*; D022423:Myeloid Cells / Q000166:cytology; D025542:Neurofibromin 1 / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000502:physiology*; D015534:Trans-Activators / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic; D025521:Tumor Suppressor Proteins; D000099185:Interferon Regulatory Factor-8; D000099232:Proto-Oncogene Protein Spi-1
chemical_list: D050836:Interferon Regulatory Factor-2; D050835:Interferon Regulatory Factors; D025542:Neurofibromin 1; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D025521:Tumor Suppressor Proteins; D000099185:Interferon Regulatory Factor-8; D000099232:Proto-Oncogene Protein Spi-1; C494229:IRF2 protein, human