Distinct modes of action applied by transcription factors STAT1 and IRF1 to initiate transcription of the IFN-gamma-inducible gbp2 gene.
A subgroup of genes induced by IFN-gamma requires both STAT1 and IRF1 for transcriptional activation. Using WT, stat1(-/-), or irf1(-/-) cells, we analyzed the changes induced by IFN-gamma in gbp2 promoter chromatin. STAT1 associated with the promoter independently of IRF1 and played an essential role in the ordered recruitment of the coactivator/histone acetyl transferase CREB-binding protein (CBP) and the histone deacetylase HDAC1. Hyperacetylation of histone 4 also required STAT1. Phosphorylation at S727 in the transactivating domain increased transcriptional activity of STAT1. In cells expressing a STAT1S727A-mutant CBP recruitment, histone 4 hyperacetylation and RNA polymerase II association with the gbp2 promoter were strongly reduced. IRF1 association with the gbp2 promoter followed that of STAT1, but STAT1 association with DNA or histone hyperacetylation were not necessary for IRF1 binding. RNA polymerase II association with the gbp2 promoter required both STAT1 and IRF1, suggesting that both proteins mediate essential steps in transcriptional activation. IRF1, but not STAT1, was found to coimmunoprecipitate with RNA polymerase II. Together, the data support the assumption that the main role of STAT1 in activating gbp2 transcription is to provide transcriptionally competent chromatin, whereas the function of IRF1 may lie in directly contacting RNA polymerase II-containing transcriptional complexes.
Ramsauer
Katrin
K
Max F. Perutz Laboratories, Department of Microbiology and Immunobiology, University of Vienna, A1030 Vienna, Austria.
Farlik
Matthias
M
Zupkovitz
Gordin
G
Seiser
Christian
C
Kröger
Andrea
A
Hauser
Hansjörg
H
Decker
Thomas
T
D000818:Animals; D002843:Chromatin / Q000187:drug effects / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics*; D005809:Genes, Regulator; D050856:Interferon Regulatory Factor-1 / Q000172:deficiency / Q000378:metabolism*; D007371:Interferon-gamma / Q000494:pharmacology*; D051379:Mice; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary / Q000187:drug effects; D012319:RNA Polymerase II / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D050794:STAT1 Transcription Factor / Q000172:deficiency / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects*; D015533:Transcriptional Activation / Q000187:drug effects*
D002843:Chromatin; C490288:Gbp2b protein, mouse; D050856:Interferon Regulatory Factor-1; C494258:Irf1 protein, mouse; D012333:RNA, Messenger; D050794:STAT1 Transcription Factor; C494080:Stat1 protein, mouse; D010768:Phosphoserine; D007371:Interferon-gamma; D012319:RNA Polymerase II; D019204:GTP-Binding Proteins; C452200:Gbp2 protein, mouse