Histone-DNA contacts in a nucleosome core containing a Xenopus 5S rRNA gene.

We describe histone-DNA cross-linking in a nucleosome core containing a Xenopus borealis somatic 5S rRNA gene. Histones H3 and H4 are cross-linked to DNA within 30 bp to either side of the dyad axis. Histones H2A/H2B and H3 are cross-linked to DNA where it enters and exists, wrapping around the histone octamer. These latter interactions extend for 80 bp to one side of the dyad axis of the nucleosome core, including the entire binding site for transcription factor TFIIIA. These extensive interactions with linker DNA might account for inhibition of TFIIIA binding and also might assist in the folding of internucleosomal DNA within the chromatin fiber.