FIG. 4.

Redistribution of nucleosomes from the MMTV NucB positioning sequence. (A) Site-directed mapping of nucleosomes assembled on the DNA fragment 18B105 results in the generation of a major signal at −127 (lane 1). Minor positions are also observed at the positions indicated by “f,” “g,” and “h.” Following thermal incubation at 62°C for 3.75, 7.5, 15, 30, and 60 min (lanes 2 to 6), new nucleosome locations are observed at −87 and later at −25. (B) Native gel electrophoresis (PAGE) results in the generation of a series of bands consistent with those observed during site-directed mapping. (C) Schematic summarizing the nucleosome movements detected in the experiments for Fig. 3 and this figure. Nucleosomes were tracked moving over the same sequences from different directions. Despite their different origins, both NucA and NucB move through the −25 and −87 positions. This suggests that DNA sequence plays an important role in determining the sites to which nucleosomes are relocated.