title: Mediator requirement for both recruitment and postrecruitment steps in transcription initiation.
abstract: Mediator complexes are required for activators to stimulate Pol II preinitiation complex assembly on an associated promoter. We show here that for the mouse Egr1 gene, controlled largely by MAP kinase phosphorylation of the ELK1 transcription factor, the MED23 Mediator subunit that interacts with phospho-ELK1 is also required to stimulate Pol II initiation at a step subsequent to preinitiation complex assembly. In Med23-/- cells, histone acetylation, methylation, and chromatin remodeling complex association at the Egr1 promoter were equivalent to that of wild-type cells, yet Egr1 induction was greatly reduced. MAP kinase activation stimulated Pol II and GTF promoter binding. However, the difference in factor binding between wild-type and mutant cells was much less than the difference in transcription, and Pol II remained localized to the promoter in mutant cells. These results indicate that an interaction with MED23 stimulates initiation by promoter bound Pol II in addition to Pol II and GTF recruitment.
authors.affiliation: Molecular Biology Institute and Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, 611 Young Drive East, Los Angeles, California 90095, USA.
authors.forename: Gang
authors.initials: G
authors.lastname: Wang
authors.forename: Michael A
authors.initials: MA
authors.lastname: Balamotis
authors.forename: Jennitte L
authors.initials: JL
authors.lastname: Stevens
authors.forename: Yuki
authors.initials: Y
authors.lastname: Yamaguchi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Handa
authors.forename: Arnold J
authors.initials: AJ
authors.lastname: Berk
mesh_terms: D000107:Acetylation; D000818:Animals; D002843:Chromatin / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D017931:DNA Primers / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000378:metabolism; D051766:Early Growth Response Protein 1; D004926:Escherichia coli / Q000378:metabolism; D005277:Fenfluramine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D017874:Immediate-Early Proteins / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008745:Methylation; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D008957:Models, Genetic; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013696:Temperature; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D002843:Chromatin; D017931:DNA Primers; D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; D006657:Histones; D017874:Immediate-Early Proteins; D014157:Transcription Factors; D005277:Fenfluramine; C001584:benfluorex