Interaction of HMG14 with chromatin.

Neutron scattering has been used to study the interaction of HMG14 with chromatin. Chromatin depleted of H1/H5 was reconstituted separately with histones H1 and H5, and complexed with HMG14. We have also studied the conformation of complexes formed by the binding of HMG14 to nucleosome dimers without linker DNA. Our data on the binding of HMG14 to linkerless nucleosome dimers argue against a significant change in the exit and entry angles of nucleosomal core DNA. Data on the condensation of chromatin into a higher-order structure suggest that there is no dramatic difference between the roles of H1 and H5 in their influence on HMG14 complex formation. However, there is a decrease of about 25% in the mass per unit length of chromatin fibers on HMG14 binding, which is not accompanied by a change in the fiber repeat distance. This is evidence that there are fewer nucleosomes per repeat in HMG14 containing chromatin fibers than in normal chromatin. Alteration of chromatin structure in this manner may be part of the role of HMG14 in actively transcribed chromatin.