Core Histone Charge and Linker Histone H1 Effects on the Chromatin Structure of Schizosaccharomyces pombe

Histones are highly conserved proteins among eukaryotes. However, yeast histones are more divergent in their sequences. In particular, the histone tail regions of the fission yeast, Schizosaccharomyces pombe, have fewer lysine residues, making their charges less positive than those of higher eukaryotes. In addition, the S. pombe chromatin lacks linker histones. How these factors affected yeast chromatin folding was analysed by biochemical reconstitution in combination with atomic force microscopy. Reconstitution of a nucleosome array showed that S. pombe chromatin has a more open structure similar to reconstituted human acetylated chromatin. The S. pombe nucleosomal array formed thinner fibers than those of the human nucleosomal array in the presence of mammalian linker histone H1. Such S. pombe fibers were more comparable to human acetylated fibers. These findings suggest that the core histone charges would determine the intrinsic characteristics of S. pombe chromatin and affect inter-nudeosomal interactions.