Complexity in transcription control at the activation domain-mediator interface.
Transcript elongation by polymerase II paused at the Egr1 promoter is activated by mitogen-activated protein kinase phosphorylation of the ternary complex factor (TCF) ELK1 bound at multiple upstream sites and subsequent phospho-ELK1 interaction with mediator through the MED23 subunit. Consequently, Med23 knockout (KO) nearly eliminates Egr1 (early growth response factor 1) transcription in embryonic stem (ES) cells, leaving a paused polymerase at the promoter. Med23 KO did not, however, eliminate Egr1 transcription in fibroblasts. Chromatin immunoprecipitation analysis and direct visualization of fluorescently labeled TCF derivatives and mediator subunits revealed that three closely related TCFs bound to the same control regions. The relative amounts of these TCFs, which responded differently to the loss of MED23, differed in ES cells and fibroblasts. Transcriptome analysis suggests that most genes expressed in both cell types, such as Egr1, are regulated by alternative transcription factors in the two cell types that respond differently to the same signal transduction pathways.
Department of Microbiology, Immunology and Molecular Genetics, Molecular Biology Institute, University of California-Los Angeles, Los Angeles, CA 90095, USA.
Michael A
MA
Balamotis
Mario A
MA
Pennella
Jennitte L
JL
Stevens
Bohdan
B
Wasylyk
Andrew S
AS
Belmont
Arnold J
AJ
Berk
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D047369:Chromatin Immunoprecipitation; D051766:Early Growth Response Protein 1 / Q000235:genetics* / Q000378:metabolism; D053595:Embryonic Stem Cells / Q000166:cytology / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D056892:Mediator Complex; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012319:RNA Polymerase II / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D050801:Ternary Complex Factors / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D048868:Adaptor Proteins, Signal Transducing; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; D008164:Luminescent Proteins; C541034:Med23 protein, mouse; D056892:Mediator Complex; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D050801:Ternary Complex Factors; D015534:Trans-Activators; D012319:RNA Polymerase II