Figure 4.
Biochemical Evidence for Looser Binding Fraction of Histones in Undifferentiated ES Cells versus NPCs.
(A) Isolated nuclei from either undifferentiated ES cells (ESC) or NPCs were extracted with increasing salt concentrations (NaCl), and the extracted fraction was detected by Western blotting. Note the increased release of both proteins from ES cells at low salt concentration. au = arbitrary units.
(B) Total histones were purified from ES cells (lanes 1 and 2) and NPCs (lanes 3 and 4) in the absence (−) or presence (+) of 0.2 M NaCl. All core histones were more readily extractable from ES cells compared to NPCs. Right: quantified densitometry of three independent experiments presented as the percentage of extracted histones ± SD. (C) Nuclei from ESCs (lanes 1-3) or NPCs (lanes 4-6) were incubated for 0, 10, or 20 min with 1 U/ml micrococcal nuclease, and supernatants were run on a 4%-20% gradient gel. Note the faster release of the histone fraction (arrow) in ESCs versus NPCs (compare lanes 2 and 5).