Figure 3

Primer extension mapping of the nucleosomes on the SL array. A) The panel on the left represents the 5' end of the nucleosome, and the right panel the 3' end. The schematics along the top edge of the extensions depict the sequence as it relates to the SL RNA gene map. Oligonucleotide C and C' were used to generate the results. The light gray and dark ovals represent total range of nucleosome protection along the sequence. Lane 1, MNase-digested chromatin; lane2, MNase-digested purified DNA; lane 3,Bss HII digested or Dra III-digested DNA, respectively; lane 4, Mock treated DNA. Arrowheads in lane 1 indicate bands resulting from nucleosome protection. The sequences below the extensions map the major 5' and 3' ends of the protected DNA. *: anomalous Bss HII digestion product. B) Schematic of nucleosome organization on the SL RNA gene array. The genomic SL RNA gene array has a regular arrangement of nucleosomes confined to the non-transcribed spacer regions. The top schematic highlights the regular ~164-bp phasing between the major PE stops. Four potential positions of the nucleosome are presented relative to the DNA sequence of the spacer region. The bottom diagram depicts the conformation of the nucleosome in the SL RNA gene array. ~180 bp encompassing the upstream promoter sequences and the transcribed region are free of nucleosome binding.