Two-hybrid analyses for the detection of a possible interaction between Act3p and yeast core histones. Plasmids encoding the listed sequences were introduced into yeast strain Y190. The growth of the transformant on the dropout media containing 25 mM 3-amino-1,2,4-triazole and no histidine after 4 d of incubation (A) and the activities of β-galactosidase (B) were examined: GAL4-DBD (control bait vector), plasmid pAS2-1 containing the GAL4 DNA-binding domain alone; GAL4-DBD-Act3p, pAS2-1 containing an additional peptide 269S–413G of Act3p, including insertion II; GAL4-DBD-Act1p, pAS2-1 containing an additional peptide 192I–310A of Act1p; GAL4-AD (control prey vector), plasmid pACT2 containing the GAL4 AD alone; H2A, H2B, H3, and H4: plasmids containing each of the yeast histone genes fused with GAL4-AD. Positive controls were plasmids containing the fused genes of the following proteins: GAL4-DBD-p53, the murine p53 gene fused with GAL4-DBD; GAL4-AD-SVT, the SV40 large T-antigen gene fused with GAL4-AD; and in B, the transformants were inoculated from media containing histidine (solid bar) or media lacking histidine (hatched bar). The data shown are the averages and SDs (error bars) of β-galactosidase activities represented by Miller units (Miller, 1972).