A major part of eukaryotic nuclear DNA is organized into nucleosomes that are not distributed randomly, but occupy defined positions with respect to the DNA sequence. Such nucleosome positioning regulates the accessibility of DNA. For example, a transcription factor binding site may be incorporated in a nucleosome and therefore be less accessible, or it may reside in a nucleosome free region and be readily bound by its corresponding factor. In our first line of studies, we wish to understand what determines nucleosome positioning. Secondly, we study the mechanism of nucleosome remodeling by which nucleosomal DNA is rendered accessible as it happens, for example, during promoter chromatin opening upon gene induction. As model systems we use the unicellular yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe and combine their powerful genetic tools with biochemical techniques.