Spin-label study of histone H1-DNA interaction. Involvement of the central part of the molecule in reconstituted chromatin.

Abstract

As shown in a previous paper [J. J. Lawrence et al. (1980) Eur. J. Biochem. 107, 263-269], covalent spin labeling of basis residues in histone H1 allows the study of the interaction of this protein with DNA. Using a step gradient dialysis procedure to reconstitute chromatin from labeled H1 and stripped chromatin, it is shown that the process of interaction of the lysine residues and DNA is the same whether histone H1 is bound to linear purified DNA or to H1-depleted chromatin. In contrast, spin labeling of the unique tyrosine of histone H1 located in the globular part of the molecule shows that this part is more involved in the interaction with chromatin than it is with linear DNA (as judged from the lengthening of the rotational correlation time). These data are interpreted as reflecting different roles for the N and C termini of the molecule of H1 and the central globular part. A model, based on these observations together with examination of the primary structures of histones H1, is proposed which accounts for the H1 involvement in the chromatosome structure.