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Genes Dev. 2018 May 1;32(9-10):711-722. doi: 10.1101/gad.314245.118. Epub 2018 May 21.

Mechanism of selective recruitment of RNA polymerases II and III to snRNA gene promoters.

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Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, 1015 Lausanne, Switzerland.
Division of Structural Biology, The Institute of Cancer Research, London SW7 3RP, United Kingdom.
Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland.
Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA.


RNA polymerase II (Pol II) small nuclear RNA (snRNA) promoters and type 3 Pol III promoters have highly similar structures; both contain an interchangeable enhancer and "proximal sequence element" (PSE), which recruits the SNAP complex (SNAPc). The main distinguishing feature is the presence, in the type 3 promoters only, of a TATA box, which determines Pol III specificity. To understand the mechanism by which the absence or presence of a TATA box results in specific Pol recruitment, we examined how SNAPc and general transcription factors required for Pol II or Pol III transcription of SNAPc-dependent genes (i.e., TATA-box-binding protein [TBP], TFIIB, and TFIIA for Pol II transcription and TBP and BRF2 for Pol III transcription) assemble to ensure specific Pol recruitment. TFIIB and BRF2 could each, in a mutually exclusive fashion, be recruited to SNAPc. In contrast, TBP-TFIIB and TBP-BRF2 complexes were not recruited unless a TATA box was present, which allowed selective and efficient recruitment of the TBP-BRF2 complex. Thus, TBP both prevented BRF2 recruitment to Pol II promoters and enhanced BRF2 recruitment to Pol III promoters. On Pol II promoters, TBP recruitment was separate from TFIIB recruitment and enhanced by TFIIA. Our results provide a model for specific Pol recruitment at SNAPc-dependent promoters.


BRF2; SNAPc; TBP; TFIIA; TFIIB; small nuclear RNA promoters

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