Non-conservative mutations are well tolerated in the globular region of yeast histone H4

Abstract

Yeast histone H4 has been mutagenized at several positions which participate in the globular core of the nucleosome. The native protein contains residues at those positions which are invariant or highly conserved over all known H4 sequences, whether from yeast, Tetrahymena or higher eukaryotes. Nonetheless the protein is tolerant of non-conservative mutations. At the level of cell function the mutant proteins cause no significant change in length of the cell cycle of mating efficiency. At the level of chromatin structure no effect is observed on the internucleosomal spacing of chromatin or the pattern of hydroxyl radical cleavage of nucleosomal DNA.