A metastable structure for the compact 30‐nm chromatin fibre

The structure of compact 30‐nm chromatin fibres is still debated. We present here a novel unified model that reconciles all experimental observations into a single framework. We propose that compact fibres are formed by the interdigitation of the two nucleosome stacks in a 2‐start crossed‐linker structure to form a single stack. This process requires that the dyad orientation of successive nucleosomes relative to the helical axis alternates. The model predicts that, as observed experimentally, the fibre‐packing density should increase in a stepwise manner with increasing linker length. This model structure can also incorporate linker DNA of varying lengths.