The core histone n-terminal tail domains function independently and additively during salt-dependent oligomerization of nucleosomal arrays

Salt- dependent oligomerization of nucleosomal arrays is related to fiber- fiber interactions and global chromosome structure. Previous studies have shown that the H2A/ H2B and H3/ H4 N- terminal domain ( NTD) pairs are able to mediate array oligomerization. However, because of technical barriers, the function( s) of the individual core histone NTDs have not been investigated. To address this question, all possible combinations of " tailless" nucleosomal arrays were assembled from native and NTD- deleted recombinant Xenopus core histones and tandemly repeated 5 S rDNA. The recombinant arrays were characterized by differential centrifugation over the range of 0 - 50 mM MgCl2 to determine how each NTD affects salt- dependent oligomerization. Results indicate that all core histone NTDs participate in the oligomerization process and that the NTDs function additively and independently. These observations provide direct biochemical evidence linking all four core histone NTDs to the assembly and maintenance of global chromatin structures.