Nucleosome positioning across differentially transcribed genes. (A), Relative nucleosome occupancy of four sets of 50 genes each with 4-, 16-, 64- and 180-fold expression levels relative to the background level during mitosis as detected by tiling microarray analysis. (B), The positioned nucleosome profile of genes is lost in the pyk1, psu1 and sks2 genes, which are expressed over 180-fold relative to the background (see text for details). Transcription from both DNA strands (−) and (+) is shown. The profile of RNA polymerase II occupancy has been previously reported .