LinkerDNA

LinkerDNA is the segment of double-stranded DNA that connects consecutive nucleosome core particles in eukaryotic chromatin. Each nucleosome core comprises about 147 base pairs of DNA wrapped around a histone octamer, leaving a variable stretch of linker DNA between core particles. The nucleosome repeat length (NRL) combines core DNA and linker DNA and typically ranges from roughly 165 to 200 base pairs in many organisms, corresponding to linker lengths of about 15 to 53 base pairs. However, linker length is highly variable between species, cell types, and genomic regions.

Functionally, linker DNA acts as a spacer that influences the packing and organization of chromatin. The length and flexibility of linker DNA affect internucleosomal interactions and the formation of higher-order chromatin structures, including models for the 30-nm fiber. The presence and distribution of linker DNA also impact DNA accessibility, and thus transcription, replication, and repair processes.

Histone H1, the linker histone, binds to the linker DNA at the entry and exit points of the nucleosome and promotes chromatin condensation by stabilizing higher-order fiber structures. H1 variants and post-translational modifications can modulate chromatin condensation and gene regulation.

In addition to structural roles, linker DNA can bear epigenetic marks and is subject to DNA methylation and other modifications that influence chromatin state. The properties of linker DNA thus contribute to the dynamic regulation of chromatin architecture across development and in response to cellular signals.