FIG. 3.

Nonpositioned nucleosomes on the HIS3 upstream elements. (A) Primer extension analysis of nucleosome positioning using a primer upstream of the HIS3 start site. Naked DNA, DNA treated with MNase in vitro (MNase Naked), and chromatin prepared from the LexA⁻ strain grown in glucose (Chm: Glu) were assayed. Similar results were obtained for chromatin obtained from the inducible LexA strain grown in galactose (data not shown). The schematic indicates the positions of the binding sites for LexA (black) and Gcn4 (white). (B) An indirect end-labeling assay of nucleosome positioning was performed with a probe downstream of HIS3 gene, DNSN, on samples from the analysis shown in panel A as well as on chromatin prepared from the inducible LexA strain grown in galactose (Chm: Gal). The gray box indicates the location of the LexA and Gcn4 binding sites.