FIG. 7.

The inferred positions of CAST and PAF53 in Pol I and their interaction surfaces for the upstream activator of rDNA transcription, UBF. Based on yeast Pol I data, the relative positions of CAST and PAF53, the mammalian orthologues of yeast A34.5 and A49, respectively, and their interaction with UBF are indicated. Yeast A49 and A34.5 subunit-specific antibody binding sites are indicated (in yellow) on the surface of the electron microscopy-derived three-dimensional model of yeast RNA Pol I, and superimposed upon this is the approximate trajectory of the DNA template (red) to illustrate the direction of transcription (white arrow) (image kindly provided by Patrick Schultz).