What is the function of linker histone H1?
Linker histone H1 binds at dyad axis where DNA enters and exits core particle, contacting both linker segments and central H3-H4 surface through globular winged-helix domain and charged C-terminal tail. By clamping incoming and outgoing linkers, H1 establishes stem structure, reduces nucleosome breathing and promotes folding of 11-nm beads-on-string into 30-nm fiber and higher-order oligomers. Dynamic exchange regulated by phosphorylation during cell cycle allows local decompaction. Although not essential for basic nucleosome formation, H1 occupancy modulates nucleosome repeat length, enhancer
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 4: Chromatin Packaging, Linker Histone H1 Function
