TFIID and human mediator coactivator complexes assemble cooperatively on promoter DNA.
Activator-mediated transcription complex assembly on templates lacking chromatin requires the interaction of activators with two major coactivator complexes: TFIID and mediator. Here we employed immobilized template assays to correlate transcriptional activation with mediator and TFIID recruitment. In reactions reconstituted with purified proteins, we found that activator, TFIID, and mediator engage in reciprocal cooperative interactions to form a complex on promoter DNA. Preassembly of the coactivator complex accelerates the rate of transcription in a cell-free system depleted of TFIID and mediator. Our data argue that this coactivator complex is an intermediate in the assembly of an active transcription complex. Furthermore, the reciprocity of the interactions demonstrates that the complex could in principle be nucleated with either TFIID or mediator, implying that alternative pathways could be utilized to generate diversity in the way activators function in vivo.
Department of Biological Chemistry, University of California, Los Angeles School of Medicine, Los Angeles, California 90095-1737, USA.
Kristina M
KM
Johnson
Jin
J
Wang
Andrea
A
Smallwood
Charina
C
Arayata
Michael
M
Carey
D002352:Carrier Proteins / Q000378:metabolism*; D002457:Cell Extracts; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA; D006367:HeLa Cells; D006801:Humans; D056892:Mediator Complex; D056913:Mediator Complex Subunit 1; D009687:Nuclear Proteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D015534:Trans-Activators / Q000378:metabolism*; D035362:Transcription Factor TFIID; D014157:Transcription Factors; D019473:Transcription Factors, TFII / Q000378:metabolism*; D014158:Transcription, Genetic
D002352:Carrier Proteins; D002457:Cell Extracts; C113182:DRIP, VDR interacting protein complex; C070633:Gal-VP16; C538855:MED1 protein, human; C491863:MED4 protein, human; D056892:Mediator Complex; D056913:Mediator Complex Subunit 1; D009687:Nuclear Proteins; D015534:Trans-Activators; D035362:Transcription Factor TFIID; D014157:Transcription Factors; D019473:Transcription Factors, TFII; D004247:DNA