Pre-RC formation is associated with the eviction of the nucleosome at the rDNA origin.

A. MNase-seq data from WT (16535) or sir2 (16668) cells arrested in G2 or G1 are shown zoomed in to allow assessment of nucleosome positioning and occupancy. Vertical lines are positioned at the border of the middle nucleosome to facilitate comparison of nucleosome placement. A nucleosome between the vertical lines competes with the pre-RC for occupancy. Positioning of this nucleosome and the two flanking nucleosomes does not change between G1 and G2. Relative read depth in the genomic region between the two vertical lines in 3A on the Y axis, is plotted according the fragment size (X-axis) in WT (B.) and sir2 mutant (C.). The large fragment sizes, that peak at approximately 160 bp correspond to nucleosome, whereas smaller fragments correspond to the pre-RC. In WT cells the nucleosome size fragments are depleted in G1 compared to G2, whereas they persist in sir2 mutant.