title: Human mediator MED17 subunit plays essential roles in gene regulation by associating with the transcription and DNA repair machineries.
abstract: In eukaryotes, holo-Mediator consists of four modules: head, middle, tail, and CDK/Cyclin. The head module performs an essential function involved in regulation of RNA polymerase II (Pol II). We studied the human head module subunit MED17 (hMED17). Recent structural studies showed that yeast MED17 may function as a hinge connecting the neck and movable jaw regions of the head module to the fixed jaw region. Luciferase assays in hMED17-knockdown cells showed that hMED17 supports transcriptional activation, and pulldown assays showed that hMED17 interacted with Pol II and the general transcription factors TFIIB, TBP, TFIIE, and TFIIH. In addition, hMED17 bound to a DNA helicase subunit of TFIIH, XPB, which is essential for both transcription and nucleotide excision repair (NER). Because hMED17 associates with p53 upon UV-C irradiation, we treated human MCF-7 cells with either UV-C or the MDM2 inhibitor Nutlin-3. Both treatments resulted in accumulation of p53 in the nucleus, but hMED17 remained concentrated in the nucleus in response to UV-C. hMED17 colocalized with the NER factors XPB and XPG following UV-C irradiation, and XPG and XPB bound to hMED17 in vitro. These findings suggest that hMED17 may play essential roles in switching between transcription and NER.
authors.affiliation: Laboratory of Gene Regulation, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Kikuchi
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Umemura
authors.forename: Saori
authors.initials: S
authors.lastname: Nishitani
authors.forename: Satoshi
authors.initials: S
authors.lastname: Iida
authors.forename: Rikiya
authors.initials: R
authors.lastname: Fukasawa
authors.forename: Hiroto
authors.initials: H
authors.lastname: Hayashi
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Hirose
authors.forename: Aki
authors.initials: A
authors.lastname: Tanaka
authors.forename: Kaoru
authors.initials: K
authors.lastname: Sugasawa
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Ohkuma
mesh_terms: D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation; D006367:HeLa Cells / Q000528:radiation effects; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D061986:MCF-7 Cells / Q000187:drug effects / Q000528:radiation effects; D056892:Mediator Complex / Q000235:genetics / Q000378:metabolism*; D010879:Piperazines / Q000494:pharmacology; D011485:Protein Binding; D021381:Protein Transport / Q000528:radiation effects; D051736:Proto-Oncogene Proteins c-mdm2 / Q000378:metabolism; D012319:RNA Polymerase II / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014466:Ultraviolet Rays
chemical_list: D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D007093:Imidazoles; C538713:Med17 protein, human; D056892:Mediator Complex; D010879:Piperazines; D014157:Transcription Factors; C482205:nutlin 3; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D012319:RNA Polymerase II