Involvement of histone H1 in the organization of the chromosome fiber.

Abstract

At high ionic strength (e.g., physiological salt concentrations) chromosome fibers [bovine lymphocytes] are 200 .ANG. in diameter and composed of discrete globular structures that are held together by histone H1. At low ionic strength the fibers unfold and appear as the familiar chains of nucleosomes (80 .ANG. in diameter). The unfolding of chromosome fibers occurs within a narrow salt range. It results from a change in the mode of the interaction between histone H1 and the chromosome fiber and is very likely the consequence of a change from cooperative binding between histone H1 and DNA to a noncooperative binding. In the non-cooperative binding state histone H1 molecules are randomly redistributed along the chromosome fiber.