Chromatin fluctuation in live mammalian cells
Structural Biology Center, National Institute of Genetics, Mishima, Japan
How is the long strand of human genome DNA organized in the cell? The DNA is wrapped around core histones, forming a nucleosome structure. The nucleosome had been assumed to be folded into a 30-nm chromatin fiber and other helical folding structures. However, several recent evidences including our cryo-microscopy (cryo-EM) and synchrotron X-ray scattering analyses have shown that chromatin mainly consists of irregularly folded nucleosome fibers without 30-nm chromatin fiber in interphase nuclei and mitotic chromosomes (1-4). This irregular folding implies a less physically constrained and locally more dynamic chromatin state. Nucleosome fibers may be constantly fluctuating. Consistent with this notion, recently we uncovered the local nucleosome fluctuation in live mammalian cells (5-6). The obtained results suggested that nucleosome fluctuation increases chromatin accessibility, which is advantageous for many “target searching” biological processes, such as RNA transcription, DNA replication and DNA repair/recombination (Figure)(5-6).
References: 1. Eltsov et al. (2008) Proc Natl Acad Sci U S A 105, 19732-19737 2. Maeshima et al. (2010) Curr Opin Cell Biol 22, 291-297. 3. Nishino et al. (2012) EMBO J.31, 1644-53 4. Joti et al. (2012) Nucleus. 3, 404-410. 5. Hihara et al. (2012) Cell Reports. 2, 1645-56
6. Nozaki et al. (2013) Nucleus 4, 3349-356
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