INFLUENCE OF DNA SUPERSTRUCTURAL FEATURES AND HISTONES AMINOTERMINAL DOMAINS ON MONONUCLEOSOME AND DINUCLEOSOME POSITIONING

Mononucleosome and dinucleosome positioning was studied in the complex es between two DNA fragments of different lengths, both containing a s trongly curved sequence from Crithidia fasciculata kinetoplast, and hi stone octamers either normal or lacking aminoterminal domains. The res ults obtained by fro III and DNase I selective digestion were: (a) The first and most stable nucleosome, formed with both types of histone o ctamers, is positioned on the curved sequence, showing a multiple dyad axis translational positioning with the same rotational phasing. This result is in very good agreement with the theoretical prediction, obt ained by adopting a method developed by us, based on the evaluation of DNA distortion energy from the nucleotide sequence. (b) The second nu cleosome has two main different positions. The first one, near the ext remity of the DNA fragment opposite to the curved sequence, presents a higher frequency in the case of normal nucleosome, whereas an interme diate position appears populated with a higher frequency in the case o f the 'tailless' nucleosome.