Construction of nucleosome cores from defined DNA sequences of prokaryotic origin.

A procedure for the de novo construction of nucleosome core particles from defined DNA sequences of prokaryotic origin is described. Efficient de novo reconstitution without added carrier DNA is demonstrated. DNase I and exonuclease III analysis of a nucleosome core prepared from a 154 base pair fragment extending from base 853 to base 1006 of pBR322 indicates a non-random positioning of the histone core along the DNA. As bacteria have no histones, their DNA cannot be expected to have a histone core positioning signal encoded in it, the efficient formation of a uniquely positioned core particle is not self evident. The possibility that a phosphate end group positions DNA fragments on the histone is considered. The de novo reconstitution of carrier-less defined nucleosome core particles should facilitate the physicochemical study of nucleosomes on the fine structural level.