Genom-wide nucleosome positioning mechanisms in the fission yeast Schizosaccharomyces pombe

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The access to eukaryotic genomic information is crucially regulated by the packaging of DNA into nucleosomes. DNA sequences incorporated into nucleosomes are much less accessible than non-nucleosomal sequences. It is still largely unclear which molecular mechanisms determine the positioning of nucleosomes along the DNA. Since recently, these mechanisms can be studied in unprecedented ways through the genome-wide mapping of nucleosome positions. This led recently and very prominently to the postulation of a universal “genomic code for nucleosome positioning”. We recently generated the first genome-wide nucleosome positioning map of the fission yeast Schizosaccharomyces pombe and did a comprehensive comparison with published data of the very distantly related budding yeast Saccharomyces cerevisiae (baker’s yeast). We found remarkable differences in nucleosome positioning, especially with regard to the role of DNA sequence, and conclude that nucleosome positioning mechanisms are evolutionarily plastic rather than universally and intrinsically DNA-encoded. As evolutionary comparisons between S. pombe and S. cerevisiae are especially revealing, and as S. pombe is more similar to multicellular eukaryotes with regard to chromatin biology than S. cerevisiae, but equally well accessible, we wish now to thoroughly study nucleosome positioning mechanisms in S. pombe.