title: Evidence for Multiple Mediator Complexes in Yeast Independently Recruited by Activated Heat Shock Factor.
abstract: Mediator is an evolutionarily conserved coactivator complex essential for RNA polymerase II transcription. Although it has been generally assumed that in Saccharomyces cerevisiae, Mediator is a stable trimodular complex, its structural state in vivo remains unclear. Using the "anchor away" (AA) technique to conditionally deplete select subunits within Mediator and its reversibly associated Cdk8 kinase module (CKM), we provide evidence that Mediator's tail module is highly dynamic and that a subcomplex consisting of Med2, Med3, and Med15 can be independently recruited to the regulatory regions of heat shock factor 1 (Hsf1)-activated genes. Fluorescence microscopy of a scaffold subunit (Med14)-anchored strain confirmed parallel cytoplasmic sequestration of core subunits located outside the tail triad. In addition, and contrary to current models, we provide evidence that Hsf1 can recruit the CKM independently of core Mediator and that core Mediator has a role in regulating postinitiation events. Collectively, our results suggest that yeast Mediator is not monolithic but potentially has a dynamic complexity heretofore unappreciated. Multiple species, including CKM-Mediator, the 21-subunit core complex, the Med2-Med3-Med15 tail triad, and the four-subunit CKM, can be independently recruited by activated Hsf1 to its target genes in AA strains.
authors.affiliation: Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA.
authors.forename: Jayamani
authors.initials: J
authors.lastname: Anandhakumar
authors.affiliation: Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA.
authors.forename: Yara W
authors.initials: YW
authors.lastname: Moustafa
authors.affiliation: Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA.
authors.forename: Surabhi
authors.initials: S
authors.lastname: Chowdhary
authors.affiliation: Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA.
authors.forename: Amoldeep S
authors.initials: AS
authors.lastname: Kainth
authors.affiliation: Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA dgross@lsuhsc.edu.
authors.forename: David S
authors.identifier: 0000-0002-7957-8790
authors.initials: DS
authors.lastname: Gross
mesh_terms: D056850:Cyclin-Dependent Kinase 8; D004268:DNA-Binding Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism*; D056892:Mediator Complex / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; C067168:HSF1 protein, S cerevisiae; D006360:Heat-Shock Proteins; D056892:Mediator Complex; C095061:RGR1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D056850:Cyclin-Dependent Kinase 8; C498309:SSN3 protein, S cerevisiae