Nonhistone Proteins HMG 1 and HMG 2 Change the DNA Helical Structure

Abstract
Two chromatin nonhistone proteins (from calf thymus) of the high mobility group, HMG1 and HMG2, reduce the linking number (topological winding number) of a circular DNA if the covalent closure of the DNA is carried out in their presence. This indicates that these proteins can either unwind the double helix, or induce a supercoiling of the DNA.