56 Large-scale alternation of nucleosome positioning potential in pericentromeric chromosome regions

It is difficult to obtain quantitative information on the protein bindings in the biological systems in the large-scale variant. We used nucleosome positioning potential (NPP) calculations on the basis of method published earlier (Fedoseyeva & Alexandrov, 2007). This method often demonstrates cluster character of NPP. Calculation of Furrier coefficients allows to analyze regional preferences of nucleosome binding. Often, the alternation of stronger and weaker binding regions takes place. Special interest deals with large-scale alteration when this may be interpreted in the terms of cellular biology. We determined them in pericentromeric regions of 2 and 3 chromosomes of Drosophila melanogaster. In one of the cases, sufficiently strong alternation of stronger and weaker NPP region was observed. The distance between nearby stronger ones is approximately 70?kbp. Fortunately, this observation may be interpreted by the competition of nucleosome with cohesin-type proteins for binding with sister chromatids. This binding maintains them side by side during appropriate stages in mitosis. The differences and likeness in NPP between left and right arms of chromosomes are discussed.