Analysis of chromatin structure from yeast with the H4G94P mutation. (A) Chromatin fractionation showing reduced amounts of histones on H4G94P genomes. Total protein extracts from equivalent numbers of cells from strains MCY073 (wild-type (WT)), MYC074 (G94A) and MCY075 (G94P) were fractionated into supernatant (S) containing soluble proteins and free histones and pellet (P) containing chromatinized proteins. Tubulin is a marker for effective separation of the supernatant and pellet fractions. Amido black staining of the membrane used for the western blots is shown below. (B) Micrococcal nuclease (MNase) accessibility is not increased in H4G94P mutants but the ladders become diffuse. Left panel, ethidium bromide stained gel of MNase treated chromatin from strains MCY091 (WT) and MCY097 (G94P) 8.5 h after repressing WT histone H4 expression (see Figure 3A). Right panel, densitometry traces emphasize the diffuse ladders of the H4G94P mutant.