Figure 6.

Histone acetylation levels of E2F-responsive genes change during the cell cycle. (A) Chromatin was prepared from synchronized T98G cells (as described in Fig. 2A) and immunoprecipitated with antibodies specific for acetylated histone H3 and acetylated H4 as described in the legend to Fig. 1. Cell cycle stages were identical to those described in Fig. 3. Parallel immunoprecipitations without antibody or with an irrelevant antibody control failed to yield detectable signals after an equivalent autoradiographic exposure (data not shown). (B) Data in A were quantitated by PhosphorImager analysis and normalized vs. input levels. The y-axis indicates fold acetylation (in arbitrary units). (Light-colored bars) acetylated H3; (dark bars) acetylated H4.