Nucleosomes are positioned on mouse satellite DNA in multiple highly specific frames that are correlated with a diverged subrepeat of nine base-pairs

Abstract

Nucleosome phasing on highly repetitive DNA was investigated using a novel strategy. Nucleosome cores were prepared from mouse liver nuclei with micrococcal nuclease, exonuclease III and nuclease S1. The core DNA population that contains satellite sequences was then purified from total core DNA by denaturation of the DNA, reassociation to a low Cot value and hydroxyapatite chromatography to separate the renatured satellite fraction. After end-labeling, the termini of the satellite core DNA fragments were mapped with an accuracy of +/- 1 base-pair relative to known restriction sites on the satellite DNA. Sixteen dominant nucleosome positions were detected. There is a striking correlation between these nucleosome frames and an internal highly diverged 9 base-pair subrepeat of the satellite DNA. The results are consistent with a sequence-dependent association of histone octamers with the satellite DNA. Our finding that histone octamers can interact with a given DNA in a number of different defined frames has important implications for the possible biological significance of nucleosome phasing.