title: Molecular characterization of celtix-1, a bromodomain protein interacting with the transcription factor interferon regulatory factor 2.
abstract: Transcriptional control at the G1/S-phase transition of the cell cycle requires functional interactions of multimeric promoter regulatory complexes that contain DNA binding proteins, transcriptional cofactors, and/or chromatin modifying enzymes. Transcriptional regulation of the human histone H4/n gene (FO108) is mediated by Interferon Regulatory Factor-2 (IRF-2), as well as other histone gene promoter factors. To identify proteins that interact with cell-cycle regulatory factors, we performed yeast two-hybrid analysis with IRF-2 and identified a novel human protein termed Celtix-1 which binds to IRF-2. Celtix-1 contains several phylogenetically conserved domains, including a bromodomain, which is found in a number of transcriptional cofactors. Using a panel of IRF-2 deletion mutants in yeast two-hybrid assays, we established that Celtix-1 contacts the C-terminus of IRF-2. Celtix-1 directly interacts with IRF-2 based on binding studies with glutathione S-transferase (GST)/IRF-2 fusion proteins, and immunofluorescence studies suggest that Celtix-1 and IRF-2 associate in situ. Celtix-1 is distributed throughout the nucleus in a heterodisperse pattern. A subset of Celtix-1 colocalizes with the hyperacetylated forms of histones H3 and H4, as well as with the hyperphosphorylated, transcriptionally active form of RNA polymerase II. We conclude that the bromodomain protein Celtix-1 is a novel IRF-2 interacting protein that associates with transcriptionally active chromatin in situ.
authors.affiliation: Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
authors.forename: A
authors.initials: A
authors.lastname: Staal
authors.forename: J M
authors.initials: JM
authors.lastname: Enserink
authors.forename: J L
authors.initials: JL
authors.lastname: Stein
authors.forename: G S
authors.initials: GS
authors.lastname: Stein
authors.forename: A J
authors.initials: AJ
authors.lastname: van Wijnen
mesh_terms: D002460:Cell Line / Q000502:physiology; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D018076:DNA, Complementary / Q000302:isolation & purification; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015870:Gene Expression / Q000502:physiology; D006367:HeLa Cells / Q000502:physiology; D006801:Humans; D050836:Interferon Regulatory Factor-2; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D010641:Phenotype; D012097:Repressor Proteins; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000502:physiology; D000092468:Bromodomain Containing Proteins
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D050836:Interferon Regulatory Factor-2; D009687:Nuclear Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C485694:BRD7 protein, human; D000092468:Bromodomain Containing Proteins; C494229:IRF2 protein, human