Nucleosome dynamics and genome evolution
Francisco Antequera, Instituto de Biología Funcional y Genómica, Consejo Superior de Investigaciones Científicas (CSIC), Salamanca, Spain

Nucleosomes are the structural units of chromatin. They facilitate the packaging of the genome inside the nucleus and modulate the accessibility of regulators to the DNA molecule. Nucleosome positioning along the genome depends on the combined contribution of several factors, which include nucleosome remodelers, the binding of regulatory proteins to DNA, and the differential affinity of nucleosomes for different DNA sequences. In the case of Schizosaccharomyces pombe, the nucleosomal profile genome-wide is largely maintained under different physiological conditions and patterns of gene expression. This relatively constant landscape favours the concentration of regulators in constitutive and inducible nucleosome-depleted regions (NDRs). We have also found that this strict positioning of nucleosomes in six species of budding and fission yeasts is associated with a species-specific nucleosomal sequence signature, which contributes critically to nucleosome positioning in the genome. These observations highlight nucleosomes as major actors in genome evolution and suggest that the variety of nucleosomal signatures among species results from the coevolution of nucleosomes and their underlying DNA sequence.

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