Chicken erythrocyte chromatin

Seki S, Nakamura T, Oda T. Supranucleosomal fiber loops of chicken erythrocyte chromatin. J Electron Microsc 1984 33 178-181. 

Taquet A, Labarbe R, Houssier C (1998) Calorimetric investigation of ethidium and netropsin binding to chicken erythrocyte chromatin. Biochemistry 37(25) 9119—9126 Temple MD, McEadyen WD, Holmes RJ, Denny WA, Murray V (2000) Interaction of cisplatin and DNA-targeted 9-aminoacridine platinum complexes with DNA. Biochemistry 39(18) 5593-5599 Terasaki T, Iga T, Sugiyama Y, Hanano M (1984) Interaction of doxorubicin with nuclei isolated from rat liver and kidney. J Pharm Sci 73(4) 524—528... 

The principles whereby a chain of nueleosomes can compact to form a 30 nm chromatin fiber are still not well understood. Nevertheless, important aspects of this process are becoming clear from imaging studies, employing both ECM and SFM. When isolated chicken erythrocyte chromatin or chromatin reconstituted onto six tandem 208 bp nucleosome positioning units were examined by ECM, a linker DNA stem-like architectural motif was observed at the entry-exit sites (Fig. 4) [30]. Particles consistent with an octamer are surrounded with 1.7 turns of DNA, a linker... 

Fig. 5. SFM images of chicken erythrocyte chromatin fibers. (A) Untrypsinized, linker histone-containing control fibers, and (B) linker histone-stripped fibers. The stripping of linker histones destroys both the three-dimensional interactions of adjacent nucleosomes and the zig-zag arrangement of consecutive nucleosomes. Trypsinization of the N-terminal histone tails of the linker histones and core histone H3 result in the loss of the three-dimensional association of the consecutive nucleosomes, but does not destroy the zig-zag configuration. Imaging of fibers deposited onto mica was performed in air under conditions of ambient humidity and temperature (from Ref. [32]). Full width of each image corresponds to 500 nm.

Fig. 8. (a) Schematic of the AFM pulling experiments and expected unraveling of an individual nucleosome as a result of pulling on the DNA. (b) Example force-extension curves on isolated chicken erythrocyte chromatin fibers redrawn from Ref [69]. (c) Idealized schematic of a typical force-extension curve obtained on pulling single titin moleeules, as in the experiments of Rief et al. [71]. (d) Explanation of the titin force curve by successive unfolding of individual protein domains (see text). 

The experimental approach used to mechanically stretch a chromatin fiber with the AFM is depicted schematically in Fig. 8a, and some example curves obtained with native chicken erythrocyte chromatin fibers are presented in Fig. 8b. These curves exhibited a saw-tooth pattern, similar to the patterns obtained upon stretching of multi-domain proteins like titin [71] or tenascin [72] (Fig. 8c). Each of... 

The missing internucleosome attraction, however, led to problems when longer nucleosome chains were simulated. Starting from an extended zig-zag conformation, folding of a 25-nucleosome chain occurred within 200 ps and the diameter of the resulting fiber-like structure was 45 nm in approximate agreement with values measured for chicken erythrocyte chromatin. On the other hand, the structure... 

Figure 6.5 Proposed condensation process of chromatin fibre based on scattering measurements of chicken erythrocyte chromatin from [7] (a) Maximally extended chromatin showing the helicoidal space arrangement, (b)-(d) Condensation of chromatin with final catenoideil space arrangement shown in (d). (e) View down the central cavity only for a portion of the chromatin chain, (f) View of the condensed arrangement for longer fibre than that of (e).

In TE bufi er, R, is about 10.0 nm for chicken erythrocyte chromatin and 7.5 nm for rat liver chromatin. These values would yield equivalent solid cylinder diameters of 28 nm and 21 nm respectively. Under these conditions, the mass/unit length for chicken erythrocyte chromatin determined relative to F-actin is 21.6 2.0 x 10 Daltons/11 nm corresponding to 0.8 0.1 nucleosomes/11 nm . ... 

Fig. 10. P-NMR spectra of DNA and nucleo-protein complexes, (a) Solid fibrous calf thymus DNA. (b) Chicken erythrocyte chromatin in solution. (c) Bull sperm heads in solution, (d) High-molecular-weight calf thumus DNA in solution. Spectra (a), (b), and (c) resulted from cross-polarization with 1-ms mix time and 1-s recycle delay. Data were acquired for 10 ms with a 2.3-mT H decoupling field. Spectrum (d) was from n/2 pulses rather than cross-polarization. From EMVeidi el al. (1981).

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