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. Author manuscript; available in PMC: 2020 Jul 1.
Published in final edited form as: J Orthop Res. 2019 Apr 25;37(7):1465–1474. doi: 10.1002/jor.24305

Figure 3: Epigenetics and chromatin organization.

Figure 3:

Epigenetic mechanisms control the accessibility of genes embedded in chromatin by altering the spatial organization of nucleosomes into higher structures including bead-on-a-string structures, 30 nm chromatin fiber and higher order chromatin loops. The nucleosome is the basic unit of organization and consists of eight histone proteins (i.e., the histone octamer which contains two each of H2A, H2B, H3, and H4) to lock two full loops of DNA (~166 bp) into place. Together with a short amount of linker DNA that extends towards the next nucleosome and another histone protein type (linker histone H1), each histone octamer organizes about 200 bp of DNA. Multiple nucleosomes together form a “beads on a string” structure that can be further folded into higher order structures in a very dynamic process that permits accessibility of DNA for transcription to proceed.