Chromosome structure at the multi-nucleosomal level has remained ambiguous despite its central role in epigenetic regulation and genome dynamics. This paper presents near-atomic resolution crystal structures of nucleosome fibers assembled from cohesive-ended dinucleosomes, with and without linker histone. Instead of folded helical '30 nm' structures, the fibers adopt open zigzag conformations that interdigitate. Linker DNA length dictates fiber configuration and packing, influenced by linker histone binding. This suggests a predisposition for nucleosome chains to interdigitate under condensing conditions, explaining observed local chromosome architecture and chromatin heterogeneity.

Zenita Adhireksan, Deepti Sharma, Phoi Leng Lee, Curt A. Davey