Fig. 2.

Changes in chromatin components during oligodendrocyte lineage progression. A, The steady-state levels of histones H2A, H2B, and H3 do not change during oligodendrocyte lineage progression. Protein lysates were obtained from proliferating progenitors cultured in bFGF (0) and from cells cultured for 6 (6), 24 (24), or 48 (48) hr in the absence of this mitogen. After separation by electrophoresis, the blots were probed with a mixture of three antibodies recognizing total histones H3, H2A, and H2B. Controls for loading of proteins were obtained probing the same blot for actin. B, The steady-state levels of histone H4 do not change during oligodendrocyte lineage progression. Protein lysates were obtained from proliferating progenitors cultured in bFGF (0) and from cells cultured for 6 (6), 24 (24), or 48 (48) hr in the absence of this mitogen. After separation by electrophoresis, the blots were probed with antibodies recognizing total histone H4. Reprobing with actin was used as loading control. C, Histones H3 and H4 are deacetylated. Protein lysates isolated from progenitor cells cultured in the presence of bFGF (0) or in the absence of mitogens for 24 or 48 hr, with (TSA) or without (24, 48) trichostatin A, were immunoprecipitated using anti-acetyl lysine antibodies (i.p. ac-lys). The blots were probed using anti-histone H3 and anti-histone H4 antibodies. D, Histone H2A and HMGN1 are deacetylated. Protein lysates were obtained from cells cultured in the conditions described in C. Samples were immunoprecipitated using antibodies recognizing acetyl lysine residues and then probed with anti-H2A, -H2B, -HMGN1, and -HMGN2 antibodies. The presence of H2A, H2B, HMGN1, and HMGN2 in the cells before immunoprecipitation was evaluated by including a whole cell lysate control (wcl).