Folding of DNA by histones which lack their NH2-terminal regions

Abstract

HeLa chromatin core particles were digested with trypsin to excise the NH2-terminal histone regions. The resulting nucleoprotein complexes were dissociated in 2.5 M NaCl; the DNA and polypeptides were then allowed to reassemble by lowering the NaCl concentration. Eighty per cent of the DNA reassociated with the polypeptides. The reassembled nucleoprotein complexes sediment at 9.7 S, have a molecular elipticity at 280 nm of 3000 degrees cm2/dmol of PO4, and contain DNase I-susceptible sites at 10 nucleotide intervals. The pattern of products generated by cross-linking the polypeptides with dimethylsuberimidate is very similar to the pattern generated by cross-linking native core particles. The results indicate that histones which lack their HN2-terminal regions retain both the features necessary for correct protein-protein interactions and the ability to fold DNA into a nucleoprotein complex resembling the chromatin core particle.