RNA polymerase II and TAFs undergo a slow isomerization after the polymerase is recruited to promoter-bound TFIID.
Transcription of mRNA genes requires that RNA polymerase II (Pol II) and the general transcription factors assemble on promoter DNA to form an organized complex capable of initiating transcription. Biochemical studies have shown that Pol II and TFIID (transcription factor IID) contact overlapping regions of the promoter, leading to the question of how these large factors reconcile their promoter interactions during complex assembly. To investigate how the TAF (TATA-binding protein-associated factor) subunits of TFIID alter the kinetic mechanism by which complexes assemble on promoters, we used a highly purified human transcription system. We found that TAFs sharply decrease the rate at which Pol II, TFIIB, and TFIIF assemble on promoter-bound TFIID-TFIIA. Interestingly, the slow step in this process is not recruitment of these factors to the DNA, but rather a postrecruitment isomerization of protein-DNA contacts that occurs throughout the core promoter. Our findings support a model in which Pol II and the general transcription factors rapidly bind promoter-bound TFIID-TFIIA, after which complexes undergo a slow isomerization in which the TAFs reorganize their contacts with the promoter to allow Pol II to properly engage the DNA. In this manner, TAFs kinetically repress basal transcription.
Yakovchuk
Petro
P
Department of Chemistry and Biochemistry, University of Colorado, 215 UCB, Boulder, CO 80309-0215, USA.
Gilman
Benjamin
B
Goodrich
James A
JA
Kugel
Jennifer F
JF
D004247:DNA / Q000737:chemistry / Q000378:metabolism; D018983:DNA Footprinting; D003850:Deoxyribonuclease I / Q000378:metabolism; D006801:Humans; D007536:Isomerism; D007700:Kinetics; D008954:Models, Biological; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D012319:RNA Polymerase II / Q000378:metabolism*; D035381:TATA-Binding Protein Associated Factors / Q000737:chemistry* / Q000378:metabolism*; D035561:Transcription Factor TFIIA / Q000378:metabolism; D035362:Transcription Factor TFIID / Q000378:metabolism*; D019473:Transcription Factors, TFII / Q000378:metabolism; D024363:Transcription Initiation Site; D014158:Transcription, Genetic
D035381:TATA-Binding Protein Associated Factors; D035561:Transcription Factor TFIIA; D035362:Transcription Factor TFIID; D019473:Transcription Factors, TFII; C066644:transcription factor TFIIE; D004247:DNA; D012319:RNA Polymerase II; D003850:Deoxyribonuclease I