A novel 66-kilodalton protein complexes with Rrn6, Rrn7, and TATA-binding protein to promote polymerase I transcription initiation in Saccharomyces cerevisiae.

We report the cloning of RRN11, a gene coding for a 66-kDa protein essential for transcription initiation by RNA polymerase I (Pol I) in the yeast Saccharomyces cerevisiae. Rrn11 specifically complexes with two previously identified transcription factors, Rrn6 and Rrn7 (D. A. Keys, J. S. Steffan, J. A. Dodd, R. T. Yamamoto, Y. Nogi, and M. Nomura, Genes Dev. 8:2349-2362, 1994). The Rrn11-Rrn6-Rrn7 complex also binds the TATA-binding protein and is required for transcription by the core domain of the Pol I promoter. Therefore, we have designated the Rrn11-Rrn6-Rrn7-TATA-binding protein complex the yeast Pol I core factor. A two-hybrid assay was used to demonstrate involvement of short leucine heptad repeats on both Rrn11 and Rrn6 in the in vivo association of these two proteins. This assay also verified the previously described strong association between Rrn6 and Rrn7, independent of the Rrn6 leucine repeat.