2003/03/21 by Helmut Schiessel, Schiessel, Helmut
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #Biomolecules (q-bio.BM) #FOS: Biological sciences #FOS: Physical sciences #Soft Condensed Matter (cond-mat.soft) #cond-mat.soft #q-bio.BM
paper · pdf · doi:10.48550/arxiv.cond-mat/0303455
topical review for the Journal of Physics: Condensed Matter, 90 pages including 24 figures
arxiv created 2003/03/21 · arxiv updated 2009/11/30
Recent progress has been made in the understanding of the physical properties of chromatin -- the dense complex of DNA and histone proteins that occupies the nuclei of plant and animal cells. Here I will focus on the two lowest levels of the hierarchy of DNA folding into the chromatin complex: (i) the nucleosome, the chromatin repeating unit consisting of a globular aggregate of eight histone proteins with the DNA wrapped around: its overcharging, the DNA unwrapping transition, the ''sliding'' of the octamer along the DNA. (ii) The 30nm chromatin fiber, the necklace-like structure of nucleosomes connected via linker DNA: its geometry, its mechanical properties under stretching and its response to changing ionic conditions. I will stress that chromatin combines two seemingly contradictory features: (1) high compaction of DNA within the nuclear envelope and at the same time (2) accessibility to genes, promoter regions and gene regulatory sequences.