Internal and higher-order structure of chromatin nu bodies
Based upon current biophysical data (including recent laser-Raman studies) of isolated nu bodies and inner histones, we have proposed that the chromatin subunit consists of a DNA-rich outer domain surrounding a protein core composed of .cap alpha.-helical-rich histone globular regions, close-packed...
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| Language: | unknown |
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2013
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| Online Access: | http://www.osti.gov/servlets/purl/7107120 https://www.osti.gov/biblio/7107120 |
| Summary: | Based upon current biophysical data (including recent laser-Raman studies) of isolated nu bodies and inner histones, we have proposed that the chromatin subunit consists of a DNA-rich outer domain surrounding a protein core composed of .cap alpha.-helical-rich histone globular regions, close-packed with dihedral point-group symmetry. Analysis of the effects of urea on isolated nu bodies suggest that these two domains respond differently: the DNA-rich shell exhibits noncooperative destabilization; the protein core undergoes cooperative destabilization. This differential response of the two regions of a nu body to a simple chemical perturbant (i.e., urea) may furnish a model for the conformational differences in nu bodies postulated for active chromatin. Nu bodies are believed to organize into 20-30 nm higher-order fibers in condensed regions of chromatin. However, the integrity of subunits in these thick fibers has recently been seriously challenged. Evidence from our laboratory, presented here, confirms that the 20-30 nm chromatin fibers consists of a close-packing of nu bodies. The chromatin subunits, therefore, retain their integrity within the higher-order fibers. |
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