In mammalian RNA polymerase I transcription, SL1, an assembly of TBP and associated factors (TAFs), is essential for preinitiation complex formation at ribosomal RNA gene promoters in vitro. We provide evidence for a novel component of SL1, TAFI41 (MGC5306), which functions in Pol I transcription. TAFI41 resides at the rDNA promoter in the nucleolus and co-purifies and co-immunoprecipitates with SL1. TAFI41 immunodepletion from nuclear extracts dramatically reduces Pol I transcription; addition of SL1 restores the ability of these extracts to support Pol I transcription. In cells, siRNA-mediated decreased expression of TAFI41 leads to loss of SL1 from the rDNA promoter in vivo, with concomitant loss of Pol I from the rDNA and reduced synthesis of the pre-rRNA. Extracts from these cells support reduced levels of Pol I transcription; addition of SL1 to the extracts raises the level of Pol I transcription. These data suggest that TAFI41 is integral to transcriptionally active SL1 and imply a role for SL1, including the TAFI41 subunit, in Pol I recruitment and, therefore, preinitiation complex formation in vivo.
- Ribosomal RNA synthesis
- RNA polymerase I
- RNA polymerase recruitment
Gorski, J. J., Pathak, S., Panov, K., Kasciukovic, T., Panova, T., Russell, J., & Zomerdijk, J. C. B. M. (2007). A novel TBP-associated factor of SL1 functions in RNA polymerase I transcription. The EMBO Journal, 26(6), 1560-1568. https://doi.org/10.1038/sj.emboj.7601601