Влияние ионов натрия и калия на конформацию линкерных участков нуклеосом

The structure of chromatin and DNA accessibility to proteins depend on the structure of DNA “linkers” entering and exiting the nucleosome. Since DNA is negatively charged, conformation of the DNA linkers, in turn, is likely affected by ionic microenvironment. Here method of fluorescence microscopy of single complexes was used to study the effect of Na+ and K+ ions on the structure of the DNA linkers. It was revealed that nucleosomes adopt one of two conformational states, and occupancy of these states is considerably changed after substitution of K+ ions by Na+. These changes are likely caused by different interaction of Na+ and K+ ions with DNA in the regions of entry and exit of DNA from the nucleosome. Cation- dependent changes in conformation of the DNA linkers can affect topological barriers in nucleosomes, structure of polynucleosome chromatin and interactions of DNA with different protein factors.