The TATA-binding protein and associated factors are components of pol III transcription factor TFIIIB.
RNA polymerases I, II, and III require the TATA-binding protein (TBP) to initiate promoter-specific transcription. We have separated HeLa TBP into four phosphocellulose fractions that elicit polymerase specificity in supplying TBP activity to TBP-depleted pol II and pol III transcription reactions. Polymerase specificity might arise in part through distinct TBP-associated factors (TAFs), which have recently been identified in pol I and II transcription. However, the requirement for pol III TAFs has not been established. Here we show that classical pol III transcription involves a minimum of two novel TAFs: TAF-172 and TAF-L. Not only does TAF-172 activate pol III transcription, but it also inhibits the binding of TBP to the TATA box, thereby repressing pol II transcription. The TBP-TAF-172-TAF-L complex can replace TFIIIB both in transcription reactions reconstituted with TFIIIC and in template commitment assays. Thus SL1, TFIID, and TFIIIB might be functionally similar TBP-TAF complexes that direct pol I, II, and III transcription, respectively.
Taggart
A K
AK
Department of Molecular and Cell Biology, Pennsylvania State University, University Park 16802.
Fisher
T S
TS
Pugh
B F
BF
D004258:DNA Polymerase III; D004268:DNA-Binding Proteins / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D009097:Multienzyme Complexes / Q000737:chemistry; D035181:TATA-Box Binding Protein; D035361:Transcription Factor TFIIIB; D014157:Transcription Factors / Q000737:chemistry*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D009097:Multienzyme Complexes; D035181:TATA-Box Binding Protein; D035361:Transcription Factor TFIIIB; D014157:Transcription Factors; D004258:DNA Polymerase III