Molecular characterization of celtix-1, a bromodomain protein interacting with the transcription factor interferon regulatory factor 2
Graduate School of Biomedical Sciences; Department of Cell Biology
Medical Subject Headings
Cell Line; Chromosomal Proteins, Non-Histone; DNA, Complementary; DNA-Binding Proteins; Gene Expression; Hela Cells; Humans; Interferon Regulatory Factor-2; Molecular Sequence Data; *Nuclear Proteins; Phenotype; *Repressor Proteins; *Transcription Factors; Transcription, Genetic
Life Sciences | Medicine and Health Sciences
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.
Rights and Permissions
Citation: J Cell Physiol. 2000 Nov;185(2):269-79. Link to article on publisher's site