Mutated His2A gene (amino acid replacements K117R/K118R/K121R/K122R, to prevent ubiquitylation) in the context of a histone gene repeat unit.
Wild-type His1 gene in the context of a histone gene repeat unit.
Wild-type His2B gene in the context of a histone gene repeat unit.
Wild-type His3 gene in the context of a histone gene repeat unit.
Wild-type His4 gene in the context of a histone gene repeat unit.