Toward Chromatin Structure

In eucaryotic cells, high compaction of genomic DNA is achieved by the com-plexation with cationic structural proteins called histones [45], DNA first wraps around the histone to form a basic unit known as nucleosome, which is 

It is likely that cells utilize the physico-chemical properties inherent in genomic DNA molecules, which are highly charged, locally stiff, and very long in the course of their functioning. Unveiling the higher-order structure and its relation with the function of DNA and chromatin is awaited. 

Albert et al., Molecular Biology of the Cell, 3rd edn. (Gerland, New York, 1994) 

Yoshikawa, Y. Yoshikawa, in Pharmaceutical Perspectives of Nucleic Acid-Based Therapeutics, ed. by R.I. Mahato, S.W. Kim (Taylor Francis, London, 2002) 

Grosberg, A.R. Khokhlov, Statistical Physics of Macromolecules, (American Institute of Physics, New York, 1994) 

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The biological relevance of this histone variant has already been discussed in Section 2.2. As it was pointed out there, the recent crystallographic structure [41] of a nucleosome containing recombinant H2A.Z (rH2A.Z) revealed structural features that pointed towards a nucleosome destabilizing role for this histone variant (see Fig. 9A-B). Two recent papers [42,375] have pursued the preliminary findings established by this paper and proceeded with the structural characterization of chromatin complexes in solution. 

Images obtained by cryo electron microscopy should in principle be able to distinguish between the structural features proposed by the different models mentioned above [16]. The micrographs show a zig-zag motif at lower salt concentrations and they indicate that the chromatin fiber becomes more and more compact when the ionic strength is raised towards the physiological value (i.e., about 150 mM monovalent ions). 

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