Site and role of the N-terminal fragment of the nucleosomal core histones in their binding to deoxyribonucleic acid as determined by vibrational spectroscopy

Abstract

The site and role of the binding of the 1-53 N-terminal part of H4 on DNA have been studied by optical spectroscopy. The structure of the 1-53 H4 fragment determined by vacuum ultraviolet circular dichroism and infrared spectroscopy is essentially aperiodic. The site of the interacion between the fragment and free DNA is localized by Raman laser spectroscopy in the small groove of the DNA, similar to the interaction site of the whole histone with DNA in nucleosomes. Infrared linear dichroism measurements show that the two 1-53 and 54-102 H4 fragments play a very important role in the histone-DNA interactions, but the roles are extremely different: the N-terminal part of the histone remains effectless on the DNA conformational flexibility and it is proposed that the structurally important interaction occurs between the globular part of the histone and the DNA. The N-terminal fragment appears to be responsible for finding the correct place on the DNA of the nucleosomal core particles.