Growth defect of orc5-1 ts in combination with histone tail mutants. In a plasmid shuffle assay, orc5-1 strain (AP121) and orc5-1 hat1 strain (AP123) were transformed with TRP-marked plasmids that contain histones H3 and H4 with lysine to arginine substitutions at different sites in their N-terminal tails. (A) Arginine substitution in H4 lysine 5, 12 shows reduced viability in combination with orc5-1 on YPD at the temperature indicated (31°C). Cells were grown for 3 days. (B) The replication defect in orc5-1 leads to efficient loss of the ADE2 marked plasmid with the covering H3/H4 wild-type genes when selection is performed on -TRP medium. When the combination of orc5-1 with histone mutants is nonviable, cells are less likely to lose the covering plasmid. Colonies were grown at 23°C. (C) Direct assays of transformation and loss of wild-type histone plasmid in different H3 mutant backgrounds. H3 histone mutants contain arginines substituted for lysines. (D) Plasmid loss assays with strains (AP182, AP183) containing wild-type histone H3 (pmp3), K9, 14, 18, 23, 27R substituted histone H3 (pmp8), and K14, 23R substituted histone H3 (pmp83). Loss rates were measured for ARSH4 (pRS316) and ARS120 (YCp120). Averages and standard deviations of three independent experiments are shown.