The mapping of nucleosomes and regulatory protein binding sites at the Saccharomyces cerevisiae MFA2 gene: a high resolution approach

We have developed an end-labelling approach to map the positions of nucleosomes and protein binding sites at nucleotide resolution by footprinting micrococcal nuclease (MNase)-sensitive sites. Using this approach we determined that the MFA2 gene and its upstream control regions have four positioned nucleosomes when transcription is repressed in mating type α cells and that the nucleosomes lose their positioning when the gene became transcriptionally active in mating type a cells. We also detected MNase-hypersensitive sites in the α2 operator region of MFA2 in α cells but not in a cells. These probably result from the change in the local DNA conformation due to protein(s) binding in this region that governs MFA2 transcription.